DNA replication in Prokaryotes & Eukaryotes (DETAILED) | Molecular Biology 🧬 & Biochemistry 🧪

Summary

This script delves into the intricacies of DNA replication, a fundamental process in cell division. It explains the stages of the cell cycle, particularly the S phase for DNA synthesis and the M phase for mitosis. The video clarifies the roles of various enzymes, the anti-parallel structure of DNA, and the significance of telomeres and centromeres. It also touches on the importance of proteins in the body and the semi-conservative nature of DNA replication, providing a comprehensive overview of the molecular biology behind cellular reproduction.

Takeaways

• 🧬 DNA replication is a crucial process that occurs during the S phase of the cell cycle, allowing for cell division and the transmission of genetic information.
• 🔬 The central dogma of molecular biology describes the flow of genetic information from DNA to RNA to proteins, highlighting the importance of transcription and translation.
• 🌟 DNA is anti-parallel, meaning the two strands run in opposite directions, with complementary base pairing (A with T and G with C), which is essential for accurate replication.
• 🌀 DNA replication involves unwinding the double helix, which is facilitated by helicase enzymes, and the formation of replication forks that extend in both directions.
• 🧵 The process of DNA replication is semi-conservative, meaning each new DNA molecule consists of one original (parental) strand and one newly synthesized (daughter) strand.
• 🌐 DNA topology plays a significant role in replication, with topoisomerases helping to manage the torsional stress that occurs as the DNA unwinds, preventing entanglement and ensuring smooth replication.
• 🔬 Telomeres are the protective ends of chromosomes that shorten with each cell division, but can be maintained or regenerated by the enzyme telomerase, preventing loss of genetic material.
• 🌿 The difference between euchromatin and heterochromatin is important for DNA accessibility; euchromatin is relaxed and accessible for transcription and replication, while heterochromatin is condensed and less accessible.
• 🌀 The centromere, a region of condensed DNA, holds sister chromatids together during the S phase of the cell cycle but splits during the M phase, allowing for the separation of chromosomes during cell division.
• 🧪 DNA polymerases are essential enzymes that synthesize new DNA strands during replication, with different types (such as DNA polymerases Alpha, Delta, and Epsilon in eukaryotes) playing specific roles in the process.

Q & A

What is the main topic of the video script?

The main topic of the video script is DNA replication, including its process, the role of various enzymes, and the significance of the semi-conservative nature of DNA replication in the S phase of the cell cycle.

What is the S phase of the cell cycle?

The S phase of the cell cycle is the phase where DNA synthesis occurs, preparing the cell for division by replicating its DNA.

What is the role of helicase in DNA replication?

Helicase is the enzyme responsible for unwinding the double helix structure of DNA, creating replication forks and allowing the DNA strands to be accessed for replication.

What is the purpose of single-stranded DNA binding proteins in DNA replication?

Single-stranded DNA binding proteins serve to stabilize the unwound DNA strands, preventing them from reannealing or being degraded by nucleases, thus maintaining the integrity of the DNA during replication.

How does the process of DNA replication ensure the accurate copying of genetic information?

DNA replication ensures accurate copying through the use of complementary base pairing (A with T, and G with C) and the action of DNA polymerases, which synthesize new DNA strands in a 5' to 3' direction based on the template provided by the parent strands.

What are Okazaki fragments and why are they significant in DNA replication?

Okazaki fragments are short stretches of RNA synthesized on the lagging strand during DNA replication. They are significant because they represent the discontinuous nature of replication on the lagging strand, which is later joined together by DNA ligase to form a continuous strand.

What is the difference between the leading and lagging strands in DNA replication?

The leading strand is synthesized continuously in the same direction as the replication fork movement, while the lagging strand is synthesized in short fragments in the opposite direction due to the 5' to 3' synthesis limitation of DNA polymerase, necessitating the use of multiple primers and Okazaki fragments.

What is the role of telomeres in DNA replication?

Telomeres are the protective caps at the ends of chromosomes that prevent the loss of genetic information during DNA replication. They shorten with each cell division, but the enzyme telomerase can help maintain telomere length, delaying cellular senescence.

What is the significance of the semi-conservative nature of DNA replication?

The semi-conservative nature of DNA replication means that each new DNA molecule consists of one original (parent) strand and one newly synthesized (daughter) strand. This ensures that genetic information is accurately passed from one generation of cells to the next.

Why is DNA replication crucial for cell division?

DNA replication is crucial for cell division because it ensures that each daughter cell receives an identical copy of the genetic material, maintaining the continuity of genetic information and allowing for growth, repair, and reproduction of cells.

What is the role of topoisomerases in DNA replication?

Topoisomerases are enzymes that manage the topological constraints of DNA during replication. They remove positive supercoils ahead of the replication fork and add negative supercoils behind it, preventing the DNA from becoming overly tangled and ensuring smooth progression of the replication machinery.

Outlines

00:00

🧬 DNA Replication Basics

This paragraph introduces the concept of DNA replication, explaining its importance in cell division. It highlights that DNA replication occurs during the S phase of the cell cycle, while cell division happens in the M phase. The central dogma of molecular biology is also discussed, emphasizing the flow from DNA to RNA to proteins. The paragraph further explains the necessity of DNA being in a relaxed state for replication, contrasting euchromatin and heterochromatin, and noting the maternal inheritance of mitochondrial DNA.

05:03

🌟 Telomeres and Telomerase

The second paragraph delves into the role of telomeres and telomerase in DNA replication. It explains that telomeres shorten with each cell division, leading to senescence, but telomerase can prevent this shortening. The paragraph also contrasts eukaryotes and prokaryotes in terms of their need for telomere synthesis and the presence of telomerase. The importance of telomerase in preventing aging and maintaining cell division is emphasized, along with the potential for neoplastic growth if telomerase activity is unchecked.

10:05

🔬 DNA Replication Process

This paragraph describes the mechanics of DNA replication, detailing the role of helicase in unwinding the double helix and the initiation of replication forks. It explains the semi-conservative nature of DNA replication, where each new DNA molecule consists of one original and one new strand. The paragraph also discusses the differences between prokaryotic and eukaryotic DNA replication, including the circular versus linear nature of DNA and the number of origins of replication.

15:06

🎧 Topology and DNA Supercoiling

The fourth paragraph explores the concept of DNA supercoiling and its impact on DNA replication. It uses the analogy of headphones to explain positive and negative supercoiling, highlighting the role of topoisomerases in managing DNA topology. The paragraph also discusses the clinical implications of topoisomerase inhibitors in treating bacterial infections by preventing DNA replication in bacteria.

20:06

🧬 DNA Replication Details

This paragraph provides a deeper look into the specifics of DNA replication, focusing on the synthesis of new DNA strands. It discusses the role of primase in creating RNA primers, the directionality of DNA polymerase activity, and the formation of Okazaki fragments on the lagging strand. The paragraph also compares the continuous nature of the leading strand with the fragmented nature of the lagging strand and the need for DNA ligase to join these fragments.

25:08

🌐 DNA Polymerases and Their Functions

The sixth paragraph discusses the different types of DNA polymerases involved in DNA replication and repair. It differentiates between the roles of DNA polymerases in prokaryotes and eukaryotes, highlighting the specific functions of DNA polymerases Alpha, Delta, and Epsilon in eukaryotes. The paragraph also explains the process of removing RNA primers and replacing them with DNA, as well as the importance of DNA ligase in joining Okazaki fragments.

30:11

🔬 Final Thoughts on DNA Replication

The final paragraph wraps up the discussion on DNA replication, reiterating the importance of the S phase in the cell cycle for DNA synthesis. It touches on the implications of uncontrolled cell replication in cancer and the role of chemotherapy in inhibiting DNA replication. The paragraph also mentions the unique role of DNA polymerase gamma in replicating mitochondrial DNA, which is inherited maternally. The speaker encourages students to practice drawing comparison tables from memory to solidify their understanding.

Keywords

💡DNA Replication

DNA replication is the process by which a cell duplicates its DNA before cell division. It is crucial for the continuation of life and is a central theme in the video. The script discusses how DNA replication occurs in the S phase of the cell cycle, emphasizing the importance of this process in cell division and the maintenance of genetic information. The video also explains the role of various enzymes, such as helicase and DNA polymerase, in unwinding and synthesizing new DNA strands.

💡Cell Cycle

The cell cycle is the series of events that lead to cell division and duplication. The script specifically mentions the S phase (synthesis) and the M phase (mitosis). The S phase is where DNA replication happens, preparing the cell for division, while the M phase is the actual division of the cell into two daughter cells. Understanding the cell cycle is essential for grasping the context in which DNA replication occurs.

💡Nucleotides

Nucleotides are the building blocks of DNA and RNA, consisting of a sugar, a phosphate group, and a nitrogenous base. The script uses the term to illustrate the structure of DNA and how new DNA strands are synthesized during replication. The video explains that DNA is made up of triple structures, with the sugar and phosphate forming the backbone and the nitrogenous bases pairing to create the double helix.

💡Complementary Base Pairing

Complementary base pairing is a fundamental aspect of DNA structure, where adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine (C). This concept is highlighted in the script to explain how DNA strands are held together and how new strands are synthesized during replication. The video mentions that A-T pairing requires two hydrogen bonds, while G-C pairing requires three, contributing to the stability of the DNA molecule.

💡Telomeres

Telomeres are the protective caps at the ends of chromosomes that prevent the loss of genetic information during DNA replication. The script discusses how telomeres shorten with each cell division and the role of telomerase in maintaining telomere length. This concept is crucial for understanding cellular aging and the potential for unlimited cell division, as seen in cancer cells.

💡Centromere

The centromere is the central region of a chromosome that holds the two sister chromatids together. The script explains that the centromere is made of heterochromatin, which is highly condensed and repetitive, providing stability. The video also discusses how the centromere splits during the M phase of the cell cycle, allowing the sister chromatids to separate and move to opposite poles of the cell.

💡Eukaryotes

Eukaryotes are organisms whose cells have a nucleus and membrane-bound organelles. The script contrasts eukaryotes with prokaryotes, highlighting differences in DNA structure and replication. Eukaryotic DNA is linear and replicates from multiple origins, while prokaryotic DNA is circular and replicates from a single origin. This distinction is important for understanding the complexity of DNA replication in more advanced organisms.

💡Prokaryotes

Prokaryotes are single-celled organisms without a nucleus or membrane-bound organelles. The script uses prokaryotes as a comparison to eukaryotes, explaining that their DNA is circular and replicates from a single origin. This contrasts with the linear DNA of eukaryotes, which replicates from multiple origins. Understanding the differences between prokaryotes and eukaryotes helps to illustrate the diversity of life and the complexity of cellular processes.

💡DNA Polymerase

DNA polymerase is an enzyme that synthesizes new DNA strands during replication. The script discusses different types of DNA polymerases, such as DNA polymerase 3 in prokaryotes and DNA polymerases Alpha, Delta, and Epsilon in eukaryotes. These enzymes are essential for the accurate replication of DNA and are a key focus in the video's explanation of the replication process.

💡Topoisomerases

Topoisomerases are enzymes that remove supercoils from DNA, preventing the DNA from becoming too tightly wound and inhibiting replication and transcription. The script uses the analogy of tangled headphones to explain the concept of torsional pressure and the role of topoisomerases in managing DNA structure. Inhibiting topoisomerases is a strategy used in some antibiotics to disrupt bacterial DNA replication.

Highlights

DNA replication is crucial for cell division and is discussed in the context of the cell cycle's S phase.

The central dogma of molecular biology, involving DNA to RNA to protein synthesis, is introduced.

DNA replication cannot extend to the end of the chromosome, leading to telomere shortening with each cell division.

Telomerase is an enzyme that can prevent telomere shortening, thus preserving genetic material.

DNA is primarily located in the nucleus, with some also found in mitochondria and chloroplasts in plants.

Euchromatin is relaxed and accessible for transcription and replication, unlike the condensed heterochromatin.

The centromere, made of heterochromatin, connects sister chromatids and is crucial for their separation during mitosis.

DNA's anti-parallel structure and complementary base pairing (A-T and G-C) are fundamental to its function.

DNA replication involves unwinding the double helix by helicase and synthesizing new strands with DNA polymerases.

The process of DNA replication in eukaryotes involves multiple origins of replication, unlike bacteria which have a single origin.

DNA replication is semi-conservative, conserving 50% of the original strands and adding 50% new strands.

Topoisomerases play a critical role in preventing DNA entanglement, which is crucial for replication and transcription.

Inhibiting bacterial topoisomerases with antibiotics like quinolones can lead to bacterial death by disrupting DNA replication.

The leading strand of DNA replication is synthesized continuously, while the lagging strand is synthesized in fragments called Okazaki fragments.

DNA ligase is essential for joining Okazaki fragments to form a continuous new DNA strand.

Different DNA polymerases have distinct roles in DNA replication and repair in both prokaryotes and eukaryotes.

Mnemonics are used to remember the functions of various DNA polymerases and other enzymes involved in DNA replication.

Cancer is associated with uncontrolled cell replication, and chemotherapy aims to inhibit DNA replication to treat it.

Understanding DNA replication is not only crucial for basic science but also has practical implications in medicine and pharmacology.

Transcripts

hey guys it's medical assistant is where

medicine makes perfect sense let's

continue our biochemistry playlist in

previous videos we talked about DNA and

RNA we talked about purines versus

pyrimidines we talked about nucleosides

versus nucleotides and we talked about

telomeres and centromeres today it's

time to delve into DNA replication how

can we replicate your DNA so that we can

replicate your cell I.E cell division

DNA replication happens here in the S

phase of the cell cycle the actual

mitosis or division of one cell into two

cells happens here at the M or the

mitosis phase s for synthesis of DNA M

for mitosis please watch the videos in

this playlist in order just like the

computer code is on the computer the

genetic code is on your DNA what's the

function to send a message to do what to

make proteins like insulin we need to

translate that message first from

meaningless codons into meaningful

proteins and there you go the central

dogma when you make another copy of DNA

it's called DNA replication this is DNA

synthesis which happens in the S phase

of the cell cycle DNA 2 RNA is

transcription if you go the other way

it's reverse transcription and then if

RNA becomes protein this is translation

also known as protein synthesis before

RNA gets translated it needs to exit the

nucleus and go to the cytoplasm can DNA

exit the nucleus and go to the cytoplasm

no because otherwise the DNA will get

degraded outside in a second okay why

did the RNA leave then why not stay

inside because your ribosomes and your

endoplasmic reticulum are outside where

is my DNA it's in the nucleus mainly but

that's not the only site we have some

DNA in the mitochondria plants have some

DNA in the chloroplast remember that you

inherited your DNA from Mommy and from

Daddy half and half but you inherited

your mitochondrial DNA only from Mommy

mnemonic mitochondria is maternal in

order for me to work on DNA it needs to

be relaxed like this exposed to the

enzymes and proteins that will help me

replicate my DNA I cannot work on a DNA

that is wrapped gazillion times on

itself and on histones such as

heterochromatin I cannot work with

heterochromatin but I can work on the EU

chromatin the difference between

neochromatin and heterochromatin was

discussed in previous videos in a

nutshell the euchromatin is relaxed it

is accessible which means transcribable

people and also replicatable and because

it's relaxed it appears lighter under

the microscope DNA is the classic

anti-parallel structure the nucleotide

is made of triple structures what do you

mean I mean sugar I mean phosphate and

nitrogenous bases complementary base

pairing because a binds with T and G

binds with C A binding with t requires

two hydrogen bond g-binding with C

requires three hydrogen bonds that's why

the GC is more stable mnemonic JC

stability what's the centromere it's the

central piece the central piece of what

the central piece of your chromosome

between the two sister chromatids how

come the centromere keeps both sister

chromatids connected and linked together

because the centromere is made of what

heterochromatin highly condensed High

really repetitive High JC content JC

equals stability so that the two sister

chromatids remain connected please

understand this the two sister

chromatids remain connected throughout

the S phase of the cell cycle throughout

the process of DNA replication they will

split however during the M phase of the

cell cycle hashtag mitosis only when the

mitotic spindle pulls them apart does

the centromere split into two halves or

two halves next telomeres Telo means the

end or the purpose as in Greek

philosophy the T loss and the logos and

the Mythos Etc too much Jordan Peterson

on this channel did you know that DNA

replication cannot extend all the way to

the end of the chromosome that's why the

end of of the chromosome contains DNA

that will not be replicated that's why

with each cycle your telomere shortens

because it's not replicated so your

telomere I.E the end piece of your

chromosome will keep getting shorter and

shorter and shorter with each subsequent

cell division unless you have a

telomerase which is a reverse

transcriptase enzyme which will make DNA

from RNA this DNA will preserve your

telomeres or synthesize new ones to be

specific I.E the telomerase will prevent

the shortening of your telomeres to

prevent the loss of genetic material

this is awesome two notes notes number

one the telomere exists at the three

prime end of your DNA only eukaryotes

need to synthesize telomere there's a

prokaryotes do not because they do not

live as long with each cell injury which

is followed by cell division trying to

regenerate and repair your tissue your

telomeres will shorten hashtag

senescence you're growing older because

of more cell division I.E more

shortening of your telomeres but

telomerase will save the day in

eukaryotes just like you and in the last

video we said what's going to happen

without telomerase as you see here I'm

shortening my telomeres and I'm aging

take it too far death but thanks to

telomerase I am preserving the telomeres

which means my cells will keep dividing

and dividing and dividing growing and

growing and growing take it too far

neoplasia as Dr Thomas Saul said there

are no Solutions in life only trade-offs

and telomerase is a classic example DNA

synthesis I.E DNA replication happens

during the S phase of the cell cycle the

synthesis phase synthesis of new DNA but

the cell division itself dividing of one

cell into two separate cells happens

during the M phase mitosis during the S

phase both sister chromatids remain

connected and linked in the middle

hashtag centromere but during the M

phase the centromere will split hashtag

mitotic spindle please pause and review

today's topic is DNA replication we are

focused on the S phase of the cell cycle

please pause and review the central

dogma let's replicate your DNA so that

we can make it into RNA so that we can

secrete proteins why do I need proteins

well let me help you with this your

insulin is a protein most of your

enzymes are proteins all of your

receptors are proteins with some

carbohydrates all of your channels are

proteins all of your pumps including the

famous sodium potassium 80 base pump are

proteins all of your carriers are

proteins the most abundant protein in

the blood albumin is a protein and

without it you will swell like a welder

Beast the second most important protein

in your plasma is globulin another

bigger protein without it no coagulation

factors you will bleed to death no

antibodies you will die from infections

no transferrin which is a protein that

carries iron in the blood oops you get

iron problems which can lead to anemia

also don't forget that proteins make

more than half of your cell membrane you

know how many cells do you have like a

hundred trillion gazillion something

like that let's take that DNA template

it and make another template another

copy synthesis that's DNA replication

occurs in the nucleus let's start I

start with my double-stranded DNA the

double helix yeah the double helix let's

unwind the Helix and open it up who's

doing this helicase helicase is the

enzyme that will unwind the double helix

oh that's a beautiful name and then what

I start with the origin of replication

and I open some replication forks next

the forks will keep forking left and

right back and forth up and down these

lovely two strands that you had are

called parent strands because they are

the original strain we will use each of

these strands to lay down New Daughter

strands why do you call them daughter

because they are new they came from the

parent who will synthesize the two new

daughter strands DNA polymerases okay

that's beautiful who's gonna help the

polymer races replisome what the flip is

that it's a complex of proteins that

help with replication oh that makes

sense I feel much better let's talk

about the difference between bacteria

and you both of you have double-stranded

DNA however the bacterial DNA is

circular in shape but your DNA is linear

that's a big difference moreover the

bacteria starts one origin of

replication but U starts multiple

origins of replication even within the

same chromosome why because you have

more genes because you have more cells

because you need more proteins in your

life you are a more complex organism who

is going to unwind the double helix

helicase in both of you who's gonna

stabilize the Unwound template strand

because listen to me the moment you

create the Gap I.E the fork this lovely

nucleotides contain nitrogenous species

these bases when they are exposed like

this not contained but exposed they are

very sticky they want to bind to

something if they bind to something

before you finish they will ruin your

DNA replication who's gonna tell them to

stop being so sticky single stranded DNA

binding proteins they will stick to

those exposed bases and tell them to

wait until we finish DNA replication

since the bacteria have circular DNA I

open a fork and before you know it I

will keep forking this way and this way

but since it's a circle they will meet

each other and before you know it we

have two DNA molecules instead of one

this is a replication however in you as

a eukaryote your DNA is linear as you

open it up via multiple origins of

replication this strand will open up and

this one will open up but remember the

two sister chromatids remain connected

at the center at the centromere as long

as we are in the S phase which is the

phase of DNA replication later when you

go to the m phase mitosis the mitotic

spindle will split the centromere into

two halves and the S phase DNA synthesis

the centromere remains intact both

sister chromatids remain connected

however when you reach the M phase the

mitotic spindle will split your

centromere into two halves and therefore

the two sister chromatids will separate

one will go to each of the two new

daughter cells that's the story of my

centromere in the S phase it is intact

and the two sister chromosome limited

remain connected however during the M

phase the centromere is split and the

sister chromatids are separated one to

each new daughter cell who did that

mitotic spindle made of what

microtubules made of what tibulin

protein and just like any other protein

it requires DNA replication

transcription and translation just to

make the tubulin just to undergo mitosis

just to replicate your cells your body

is amazing two parent strands I already

had those however we will use each one

as a template to synthesize a new strand

so at the end of the day the two parent

strands remain but we added two New

Daughter strands that's why we say that

DNA replication is

semi-conservative because we conserved

50 percent from the past and we added 50

percent the two new daughter strains

that's why we can call DNA another name

we called it negatively charged we

called it polar we called it

anti-parallel we called it nucleic acid

we called it possessing complementary

base pairing now let's call it

semi-conservative replicator let's

review DNA replication occurs in the S

phase of the cell cycle let's start with

the double-stranded DNA amazing and then

start an origin of replication or many

because I'm a human being opening those

replication forks keep forking this way

and this way thank you so much helicase

for unwinding the double helix in both

directions the moment you open up your

DNA those bases are sticky and they want

to stick to anything who's gonna protect

me from this disaster the answer is a

single stranded DNA binding proteins

which serve two functions function

number one they prevent the newly

separated bases from sticking to

something else and ruining the DNA

replication the second function is that

they prevent the destruction of DNA by

the nasty nuclease enzyme why do we call

it nucleus because it's an enzyme that

destroys the nucleus why do I care as a

DNA because DNA is in the nucleus doofus

that's why it's called nuclease Thank

you so these single stranded DNA binding

proteins are amazing yeah because they

are proteins that bind to the single

strand after separation I get it what's

the first order of business add a primer

what the flip is that short RNA about 10

nucleotides so to speak how can I make

this primer which is RNA primase will

make it for for you in which direction 5

Prime to three prime just like how DNA

polymerase works next my favorite part

of the video the super coils here is the

story get your lovely headphones the

ones with wire not the Bluetooth ones

not your earbuds the classic ones from

the good old days they are thin and

linear according to the science of

topology a branch of mathematics if

anything is thin and linear torsional

pressure will happen that's why the

moment you put your headphones in your

backpack and come back to retrieve them

two days later or so you will find your

headphones in Tangled together what the

flip I straightened them out before I

put them in the backpack I swear I did

straighten them out how come they're

entangled like this torsional pressure

baby topology what do we call is

positive super coils okay now what are

you going to do with your headphones now

well I gotta use them so I will

disentangle them how did you do it you

did it via adding negative super coils

which is a technical term for removing

the positive super coils or

counteracting the positive super coils

so that you disentangle and straighten

up your headphone wires again let me

take you back to ancient Greece what

does time and space mean let's start

with time time is called Chrono that's

why we talk about chronic diseases

diseases that last for a long time how

about space space in Greek is toppo so

Topo means space yeah because your

headphones got entangled in space due to

torsional pressure that act upon them in

Space by the same flipping token your

DNA has double strands it is thin it is

long by the laws of nature it should

entangle like this if my DNA is

entangled like this hashtag positive

super coils do you think I'll be able to

replicate it no do you think I'll be

able to transcribe it no do you think

I'll be able to translate it into

meaningful proteins also no no proteins

no cell division no cell functions you

are toast because you're straightened

DNA got converted to the evil

topoisomer isomer and chemistry means

similar yeah it is similar it still

contains the same nucleotides and

nucleosides everything is there the

genetic code is there it just has a

different orientation in space rendering

it useless so if your DNA got entangled

you are finished but hi Miracle says how

come I survived all of these years

because you have a topoi summer race

that will disentangle your DNA I.E

prevent it from being entangled in the

first place how did it do it and instead

of adding positive super coils let's do

the opposite add negative super coils

I.E prevent the coiling but wait it gets

better let's make it clinical do you

want to destroy bacteria oh yeah those

disease-causing bacteria the bad one of

course I want to punch him in the face

easy inhibit their topoi summer Race by

giving medications that are

topoisomerase Inhibitors such as

quinolones AG

levofloxacin

moxifloxacin

oxyfloxacin

ciprofloxacin and other antibiotics by

inhibiting their topoisomerase these

bacteria will be left in this state I.E

entangled do you think this bacteria can

divide no no cell division the bacteria

is toast because the life span of the

bacterium is very short that's why give

the patient a week on those quinolones

and boom the pneumonia is gone or the

urinary tract infection is gone because

without replication the people I mean

the bacteria perish this is the beauty

of topology

microbiology and molecular biology why

don't they teach like this in school

biochemistry makes so much sense once

you understand what the flip you're

talking about yet today we have doofuses

with stethoscopes running around saying

oh why do I need to study molecular

biology I will be working in the ICU at

the hospital I am not trying to invent a

new drug doofus it's because you were

work at the ICU at the hospital that you

need to learn this because if an

organism does not possess to isomerase

then giving quinolone antibiotics to

them is pointless isn't it to learn more

about quinolones and other antibiotics

download my antibiotics course at

medicosisperfectsnetis.com it will teach

you about antibacterials antivirals

antifungals and anti-parasitic

medications back to DNA replication what

should I do to my double-stranded DNA

open it up

helicase and then what add primers short

RNA segments who's going to add them DNA

primase We'll add the primers and then

what who's going to make the new DNA the

daughter strands answer DNA polymerases

but please pay attention one of your

parents dnas was three prime to five

Prime and the other one was five Prime

to three prime your DNA polymerase the

synthesizer of new DNA only puts no

nucleotides in the five Prime two three

prime Direction which means it reads

from the three prime to five Prime

template it will read this template 3 to

5 and synthesize the complementary

segment 5 Prime to three prime okay as

you see here the helicase is opening it

up this way keep opening it up opening

it up opening it up and Mr DNA

polymerase is adding The New Daughter

strand here with a beautiful single

stride hashtag leading strand okay but

we have a problem on the opposite side

this Hiller case will open up your DNA

it will Cruise like a sharp knife in

warm butter as it cruises it opens up no

segments but remember your DNA

polymerase only works five Prime to

three prime so it will start here and go

here and then my helicase will open more

so we'll add another segment and it will

open more it will add another segment

why didn't we do it in a single stride

just like the leading strand because the

helicase hasn't opened the entire DNA

yet so we have to put it in fragments

who discovered these fragments a famous

Japanese scientist named akazaki that's

why we call them okazaki fragments why

does Japan has this flag because the

Land of the Rising Sun who is gonna bind

and ligate and join these okazaki

fragments together to make a continuous

strand DNA ligase well now let's compare

between the leading Strand and the

lagging strand the leading strand is

continuous one single stride the lagging

strand is fragmented the leading strand

is comp complementary to the parental 3

Prime to five Prime strand but the

lagging strand is complementary to the 5

Prime to three prime parent strand okay

leading strand is continuous no need for

DNA ligase how about lagging strand it

needs DNA ligase I am not saying that

the leading strand will never need DNA

like this it will need DNA like this as

we'll discuss later in the next video on

DNA repair when you try to repair a

piece of DNA of course you will like it

I'm just trying to keep it simple

lagging strand of course needs DNA

ligase way more than the leading strain

leading strand because we started at one

point we'll need one primer this is

theoretical in reality it needs more

than this but we're keeping it simple

lagging strand however needs many

primers there is a crazy mnemonic that I

invented if you may forgive my language

I was going to say the lagging strand is

is a boot licker but I said let me have

some respect for myself and make it an

expensive boot Gucci liquor G with the

G's and L with the L lagging is a Gucci

liquor not just that it's a chattered

goatee liquor why because it is

dependent on others it's dependent on

the DNA ligase it will lick its boot and

it's dependent on multiple primers which

means multiple primases it will lick

their boot now our comparison table is

getting longer enzyme needed to make the

primer which is RNA in the prokaryotes

it's primase in the eukaryotes also

primase the enzyme needed to synthesize

DNA The New Daughter strands in

prokaryotes it's DNA polymerases in

eukaryotes DNA polymerases but to which

polymerase I am glad you asked if you

want to synthesize new DNA which are the

daughters strand ends in prokaryotes

we're using DNA polymerase 3. in the

eukaryotes you're using DNA polymerases

Alpha Delta and Epsilon let's add some

mnemonic remember that making new DNA

means synthesizing no no clear tides and

remember the nucleotide is a Triad a

trio of sugar

nitrogenous base and phosphate so

nucleotide three components that's why

we have DNA polymerase 3 and we have

three different DNA polymerases in

humans what are those three DNA

polymerases Alpha Delta Epsilon mnemonic

add new DNA this Delta you can pronounce

it like a d and we are adding no DNA

next if you want to remove the RNA

primer in either one we're using 5 Prime

to 3 Prime exonuclease let me remind you

of something remember that we added the

primer via primase in the five Prime to

three prime Direction so it makes sense

to remove it by going in the same

direction 5 Prime to 3 Prime

exonuclease also remember that the DNA

polymerases added DNA in the five Prime

to three prime so it all makes sense we

always go from the 5 Prime to 3 Prime

whether you are making new DNA new

primer or removing a primer however this

five Prime three prime

exonuclease enzyme has different names

in prokaryotes and eukaryotes in

prokaryotes we call it DNA polymerase

one in eukaryotes is the rnas H because

it's an enzyme that's removing RNA why

do they call it age maybe it's

alphabetical but a mnemonic is hella in

German means lighter when you make it

lighter you're removing stuff I am

removing the RNA to make it lighter do

you have a mnemonic for the DNA

polymerase one yeah easy remember it's

always harder to build up than to tear

down tearing someone down is easy

building up people is different that's

why tearing down took just DNA

polymerase one but building up requires

three that's how I remember it I know

it's weird next after removing the

primer which is RNA how can I replace

this RNA with DNA well DNA polymerase

one again and DNA polymerase Delta here

how do I remember it Delta in Greek

looks like s in English so this is the

enzyme that will swap DNA for RNA

meaning substitute DNA for RNA IE remove

the r RNA throw it in the trash and add

DNA instead let's look at it in a

different way let's talk about the

prokaryotes alone and then the

eukaryotes alone first DNA polymerases

in prokaryotes we have DNA polymerase

one two and three forget two it's not

important for your exam just focus on

one and three DNA polymerase one it's

easier to tear down after you tear down

that RNA replaced with DNA oh so it has

two functions yes it has two functions

in prokaryotes and then you build up

with the DNA polymerase 3 synthesizes no

DNA amazing we're done next eukaryotes

giselian polymerases let's just focus on

five these are not the only one there is

more Alpha Beta Gamma Delta Epsilon I

made a mistake here I should have

written them as Alpha Beta Gamma Delta

Epsilon I made a mistake I apologize my

proofreading mechanisms are are not as

robust as my DNA ones more on that in

the next video DNA polymerases Alpha

Delta and Epsilon will add no DNA IE DNA

synthesis DNA polymerases beta and

Epsilon will help us repair the DNA

which is the topic of the next video DNA

polymerase gamma replicates not the

nuclear DNA of your nucleus the

mitochondrial DNA of your mitochondria

remember that you inherited the

mitochondrial DNA only from your mother

it's purely maternal not paternal

mnemonic gamma Gaga Imagine That Lady

Gaga is your mama mitochondrial DNA

honestly I would rather throw a Viper

down my shirt than have Lady Gaga as my

mom AZ medicosis chilled down we're done

with DNA replication just don't forget

that we cannot replicate the last part

we cannot extend the replication all the

way to the end of the chromosome that's

why we have a telomeres without

telomerase your telomeres will keep

shortening and shorting and shortening

and you grow old not just as a person as

a cell and the cell that is getting

senescent is going to die thankfully you

have telomerase as a eukaryote but

prokaryotes do not their lifespan is not

that long they do not need it anyway and

the comparison table is getting longer

who's gonna join my okazaki fragments

DNA ligase whether it's prokaryotes or

eukaryotes who's gonna remove the

positive super coils I.E add negative

super coils DNA Tuple isomerases next

Who's Gonna synthesize the telomeres to

prevent the shortening of the telomeres

well in eukaryotes is the telomerase in

prokaryotes there is nothing it does not

apply there so we can write n a here

just like Bank of America if you want to

be an excellent student bring a piece of

paper and draw this table from scratch

from memory without looking you're

allowed to copy this you can look while

copying the point of comparison and do

the same thing for this second table

from scratch on paper finally some

pearls for the pros DNA replication took

place in the S phase of the cell cycle

cancer is uncontrolled replication of

your cells due to errors or mutation

chemotherapy is the opposite

chemotherapy is trying to treat cancer

by inhibiting replication of your DNA

some antibacterials and antivirals will

try to kill bacteria or kill viruses by

inhibiting their DNA not yours to learn

more about oncology I.E cancer and the

anti-cancer Pharmaceuticals and their

mechanisms download my anti-cancer

pharmacology course to learn how your

beautiful kidneys work download my renal

physiology course here is a question for

you would you consider the cells of your

kidney as labial cells stable cells or

quiescent cells let me know the answer

in the comment section in the meanwhile

Please Subscribe hit the bell and click

on the join button you can support me

here or here go to my website to

download my courses be safe stay happy

study hard this is medicosa's perfect

status where medicine makes perfect

sense