Topic 8: RNA Structure and Transcription
Summary
TLDREste video analiza el dogma central de la biología, que explica cómo el ADN se convierte en proteínas a través de dos procesos: transcripción y traducción. La transcripción ocurre en el núcleo, donde el ADN se copia en ARN mensajero (ARNm), y la traducción sucede en el citoplasma, donde el ARNm se convierte en proteínas. Se explican las diferencias entre el ADN y el ARN, así como los tipos de ARN involucrados en este proceso. Además, se introduce la regulación de la expresión génica, destacando los factores que influyen en la transcripción y cómo se procesan los intrones y exones en el ARN.
Takeaways
- 🧬 El dogma central explica cómo el ADN se convierte en proteínas mediante dos procesos: transcripción y traducción.
- 📜 La transcripción ocurre en el núcleo y convierte ADN en ARN mensajero (ARNm).
- 🔄 La traducción ocurre en el citoplasma y convierte el ARNm en proteínas.
- 🔬 El ARN es un ácido nucleico que actúa como intermediario en la producción de proteínas.
- 🌐 El ARN tiene uracilo en lugar de timina, lo que lo diferencia del ADN.
- 🧩 En la transcripción, el ARN mensajero se empareja con bases complementarias del ADN: G con C, A con U.
- 🚶♂️ La transcripción tiene tres etapas: iniciación, elongación y terminación.
- 🔗 La ARN polimerasa es responsable de desenrollar el ADN y formar el ARNm.
- ✂️ Los intrones se eliminan y los exones salen del núcleo para convertirse en ARNm maduro.
- ⏳ La degradación del ARNm regula la expresión genética, ya que afecta cuánto tiempo se traduce en proteínas.
Q & A
¿Qué es la dogma central de la biología molecular?
-La dogma central de la biología molecular explica cómo el ADN se convierte en proteínas a través de dos procesos: la transcripción (ADN a ARN) y la traducción (ARN a proteínas).
¿Dónde ocurren la transcripción y la traducción en la célula?
-La transcripción ocurre en el núcleo, mientras que la traducción ocurre en el citoplasma.
¿Cuál es la principal diferencia entre ADN y ARN?
-El ADN contiene desoxirribonucleótidos y tiene timina como base, mientras que el ARN contiene ribonucleótidos y usa uracilo en lugar de timina.
¿Qué es el ARN mensajero (mRNA) y cuál es su función?
-El ARN mensajero (mRNA) es una molécula intermedia que transporta la información genética del ADN al ribosoma para la síntesis de proteínas.
¿Qué son los intrones y exones en el proceso de transcripción?
-Los intrones son secuencias no codificantes que se eliminan del ARN antes de que este salga del núcleo, mientras que los exones son las secuencias que permanecen y codifican para proteínas.
¿Qué papel juega la ARN polimerasa en la transcripción?
-La ARN polimerasa es la enzima responsable de unir y copiar la hebra de ADN en ARN durante la transcripción, tanto desenrollando el ADN como haciendo el apareamiento de bases complementarias.
¿Qué es el proceso de iniciación en la transcripción?
-La iniciación es el primer paso de la transcripción en el cual la ARN polimerasa se une a una región promotora en el ADN para comenzar a sintetizar ARN.
¿Qué sucede durante el proceso de elongación en la transcripción?
-Durante la elongación, la ARN polimerasa se desplaza a lo largo del ADN y sintetiza una cadena de ARN utilizando el apareamiento de bases complementarias.
¿Qué ocurre en la etapa de terminación de la transcripción?
-En la terminación, la ARN polimerasa llega a una secuencia de terminador en el ADN, lo que hace que se detenga la transcripción y se libere el ARN recién sintetizado.
¿Cómo se procesa el ARN antes de salir del núcleo?
-El ARN recién transcrito se somete a un procesamiento que incluye la adición de un caperuza en el extremo 5', una cola poli-A en el extremo 3' y la eliminación de intrones, dejando solo los exones.
¿Qué es la traducción y dónde ocurre?
-La traducción es el proceso por el cual el mRNA se utiliza para sintetizar proteínas. Ocurre en el citoplasma, específicamente en los ribosomas.
Outlines
🧬 Central Dogma y Proceso de Transcripción
El primer párrafo explica el concepto de la Dogma Central, que describe cómo el ADN se traduce en proteínas. Se mencionan dos procesos principales: Transcripción (de ADN a ARN) y Traducción (de ARN a proteína). La Transcripción ocurre en el núcleo y la Traducción en el citoplasma. Se destaca la importancia de los genes como regiones específicas del cromosoma que codifican proteínas. Se explica la diferencia entre ADN y ARN, destacando que el ARN es una molécula intermedia que lleva la información proteica y puede catalizar algunas reacciones. Se presentan los tipos de ARN: mensajero (mRNA), de transferencia (tRNA) y de la ribosoma (rRNA).
🍪 Genes como Recetas y Proceso de Transcripción
El segundo párrafo compara los genes con recetas, explicando cómo cada gen se puede considerar una receta para producir una proteína específica. Se describe el proceso de Transcripción como la fotocopia de una receta para no dañarla. Se menciona que, al igual que las recetas, solo se transfiere una parte del ADN (el gen) a ARN para su posterior traducción a proteínas. Se enfatiza la importancia de la Transcripción como el paso intermedio entre el ADN y las proteínas, y cómo la secuencia de bases en el ADN determina la secuencia en el ARN.
🔬 Detalles del Proceso de Transcripción
En el tercer párrafo se explican los detalles del proceso de Transcripción, que incluyen la iniciación, la elongación y la terminación. Se describe la función de la RNA polimerasa, que actúa como un enzima promotor y catalizador del proceso. Se menciona la importancia de la región promotora en el inicio de la Transcripción y cómo solo una cadena del ADN se utiliza como plantilla para la síntesis del ARN. Se aborda la terminación del proceso cuando se alcanza la secuencia terminadora, despidiendo la RNA polimerasa y liberando el ARN completo.
🧬 Regulación de la Expresión Genética
El cuarto párrafo trata sobre la regulación de la expresión génica, que comienza en el núcleo de las células eucariontes. Se describe cómo ciertos genes están compactados y no pueden ser transcritos, mientras que otros están disponibles. Se explica el proceso de maduración del ARN mensajero, incluyendo la eliminación de intrones y la formación de exones, lo cual permite que el ARN salga del núcleo y se traduzca en proteínas. Se mencionan los factores de transcripción que ayudan a regular la expresión génica y la importancia de la esplicación alternativa para crear diferentes proteínas a partir del mismo ARN.
🌐 Regulación de la Expresión Genética y Proceso de Traducción
El quinto párrafo profundiza en la regulación de la expresión génica, mencionando mecanismos como la retención del ARN mensajero en el núcleo y la degradación del ARN. Se discute cómo la actividad de las proteínas y su capacidad de ser correctamente doblegadas y ubicadas también influyen en la expresión génica. Se hace una revisión del proceso de Transcripción y se establece la conexión con el proceso de Traducción, que es el siguiente paso en la conversión del ARN mensajero en proteínas.
➡️ Proceso de Traducción y Función del ARN
El sexto párrafo concluye el video explicando cómo el ARN mensajero, una vez procesado y maduro, se dirige al citoplasma para iniciar la Traducción. Se describe cómo el ARN se une a la ribosoma y se traduce en una cadena de aminoácidos que formará la proteína. Se enfatiza la importancia de que el ARN esté listo para la Traducción y cómo los intrones son eliminados para que solo queden los exones, que especifican los aminoácidos.
Mindmap
Keywords
💡Dogma central
💡Transcripción
💡Traducción
💡ARN mensajero (ARNm)
💡ARN de transferencia (ARNt)
💡Promotor
💡ARN polimerasa
💡Exón
💡Intrón
💡Cap y cola poli-A
Highlights
Introduction to the central dogma of molecular biology and its two processes: transcription and translation.
Explanation of where transcription and translation occur within a cell.
Description of the role of DNA and genes in protein production.
Differences between DNA and RNA, including the sugar component and base pairing.
The function of RNA in protein synthesis and its three types: mRNA, tRNA, and rRNA.
Analogy of genes to recipes in a cookbook, explaining gene expression.
Process of transcription from DNA to messenger RNA (mRNA).
The three steps of transcription: initiation, elongation, and termination.
Role of RNA polymerase in the initiation of transcription.
Mechanism of elongation in transcription where RNA polymerase synthesizes RNA.
Termination of transcription and the release of mRNA.
Gene regulation starting in the nucleus and its impact on gene expression.
Difference between prokaryotic and eukaryotic cells in terms of transcription and translation.
Importance of RNA processing, including the removal of introns and addition of a cap and tail.
The role of transcription factors in regulating gene expression.
Differentiation between exons and introns and their role in mature mRNA formation.
Regulation of gene expression through RNA export and degradation.
Importance of protein folding and stability in gene expression.
Overview of the transcription process and its significance in gene expression.
Transcripts
foreign
hi everybody so as you remember this is
going to be the second part of this
discussion and we are going to actually
dig into the central dogma which again
explains how DNA is encoded into
proteins
as a reminder there are two processes
processes to the central dogma the first
one is when DNA goes to RNA specifically
we're going to look at messenger RNA and
this is called trans
description
and the second part taking messenger and
RNA to protein is called translation
transcription happens in the nucleus
translation happens in the cytoplasm
so protein production always starts with
DNA and what it essentially starts with
is a gene that is a small region of
amdna that's in part of a chromosome
right the sequence of DNA in each gene
is what's going to encode or be the
specific protein that we make
so in order for proteins to be produced
it requires this kind of intermediate
molecule called RNA RNA is a nuclear
nucleic acid as a review from what we
looked at at the beginning of the
semester when we looked at biomolecules
but how are they different from DNA well
a big part if you look here are
the areas on the bottom and when we're
talking about five Prime three prime
we're looking at this is a very first
carbon because this is where the base
would be attached if we add the sugar so
that's one that's two that's three four
and five
so on the second one you'll notice in
DNA it's called deoxy
ribonucleic acid because d means it's
without an oxygen which is there
so that's one way that it's different
right and when we talked about three
prime I said when you looked at 3 Prime
there's always a hydrogen is the last
atom well it's true but if you look at
it it's fully the o h that's there at
the end and then essentially what will
happen up here is you'll get that
phosphate that's there
so when we look at the sugar that's the
difference on the sugar now a big thing
that we'll notice and you can easily
tell for sequence of an RNA if you have
DNA or RNA because if you have DNA you
have thymine
and if you have RNA you have uracil
so when we look at this G's and C's
still base pair with each other but
anywhere you have a t you would now have
a u in your messenger or name
so if you have a DNA sequence this is
our DNA
that has c g t and a
your messenger RNA
would then be still G
it would be C where T is it would be a
but where a is it would now be U
so you can put this together the same
way as you do your complementary DNA
sequence it's just wherever you would
have a t you'd replace it with a u
now that makes a big difference in terms
of what we have here because what we
have if you look
here messenger RNA tends to be single
stranded and then DNA we know it's
double-stranded
and it also is different in its function
so it encodes in DNA storage for RNA and
protein encoding information and
transfers information to next generation
of cells or RNA carries protein accorded
information and helps to make proteins
specifically it even can catalyze some
reactions
so there are three types of RNA
we have messenger RNA which is when we
look at the central dogma that's where
we go DNA
2 RNA
Transfer RNA is going to be what helps
to make
RNA
2 protein
so it's going to be what actually helps
carry the information or carry the amino
acids to make the protein
and there are RNA that's part of the
ribosome specifically
and this is where translation is going
to occur so there are different types of
RNA molecules and shorthand for
Messenger rnas mRNA for transfer rna's
TRNA and for ribosomal it's RNA there
are other types of RNA but that is for a
more advanced class to discuss those
so I like to think about genes being
like a recipe in a good cookbook and
when I talked about this earlier in the
semester I compared it to my mom's
recipes
my mom was a fantastic cooking Baker I
grew up as a child on a farm
in Iowa we didn't have a whole lot of
money so my mom made everything from
scratch so when she passed away from
cancer it was really really important
that I get something that I felt was
what reminded me of her a part of her
and that I really identified with so I
took all her recipe boxes and everything
so all her recipe boxes in her big
recipe box has these individual recipe
cards
so the whole box itself
would be like this cookbook here oops
it has every single recipe that she ever
made kind of consistently that she
didn't have stored in her brain right
just like this cookbook does it has
multiple recipes in it so that would be
like our chromosome with a lot of genes
on it but we don't want to cook the
entire recipe in the box or all the cook
recipes in the cookbook we only want to
make brownies so we're going to take out
one recipe and then we are going to make
a photocopy of that
now I think about in terms of my mom's
box
I don't want to I don't like really
cooking with them because I'm scared I'm
gonna mess them up and once I mess them
up they're gone forever and they make so
much they're very very
um close and dear to me because a lot of
them are handwritten by her and so it
makes me feel extremely close so I
wouldn't want anything to go wrong with
it so I like to make copies of them
so this is what it's showing here is
that copy of that one brownie recipe
right the great thing is is if I make a
copy of it and I decide not to make the
recipe I can throw it away it's no big
deal
so if there are signals that say I need
to make this protein but then ends up
being so that we don't need to
necessarily make it the bot the cell
will just destroy it and it's no loss
right because we have the original
recipe or Gene still in the nucleus
now when we want to make that brownie
recipe we have to basically put things
like flour and sugar and salt and cocoa
and butter and eggs
all of those individual things would be
like the amino acids that we're using
here
4r
protein so we're going to bring all
those different amino acids make our
batter and cook it and so when we
actually get our protein
ready or you know done that's equivalent
to having our brownies ready to be eaten
or used however we need to
so the process of making the photocopy
because we stay in the same language is
transcription and the process of taking
that photocopy and making it actually
into our brownies is translation
foreign
is a process of taking DNA and creating
RNA
and so um
basically with DNA going to messenger
RNA we are staying in the same type of
biomolecule which is a nucleic acid
so what I want you to do here and you
can see in the description below that
there is a video and you you're just
going to watch this and it's going to
take you through the central dogma
overview what we're going to talk all
the way from DNA to protein but what
we're going to focus on next after you
watch this to get an idea what we're
about to talk about
is
transcription
so in transcription DNA sequences
determine the RNA sequence so when we
want to make RNA what I was talking
about earlier base pairing takes place
between the RNA and the DNA molecule
and we use complementary base pairing
oh if we look we do complementary base
pairing
basically if we have a piece of DNA that
has a c g and T as we know if we were
doing another piece
of DNA here
the complementary base pairing would be
t
n 4 C right G and four g c and four
thymine a those would be the DNA
complementary base pairing
now when we go to take DNA
and we base per with RNA we get you for
your cell C still base pairs with G that
doesn't change from what we saw here
G still base pairs with C and thymines
still base pairs with adenine so
basically we just replace
all RTS n d and hay
with use for RNA
and basically these if we go through and
make base pairing RNA to RNA
we follow the same rules that we did
from when we went from DNA to RNA as you
can see we already have uracil in our um
in our RNA there so it will base pair
with adenine
and here again adenine will base pair
with uracil
now that's base pairing how do we make
this messenger RNA to begin with
well there are three steps that take
place initiation
elongation and termination
so let's talk about each one of these
so in transcription initiation RNA
polymerase gets started as you remember
enzymes always tell us what we do so it
starts it ends with an ace that's how we
know what essentially
um
we have an enzyme and then it's telling
us what it makes which is RNA polymer
right so in if you remember when we were
in DNA replication we had DNA polymerase
because it was making a DNA polymer
so what happens here
is here
is the gene we want to make
now just like if you are a you know
someone who's new in the music field you
want your career to get started you want
people to know you and get everything
like maybe you want to get things booked
right venues
um get on the TV get on the radio so you
hire a promoter to basically get your
career started so think about this we
have what's known as the very first area
here a promoter region
and this is where our enzyme
will bind
to start
transcription which makes sense we're
starting transcription right because
we're at initiation
so we're starting the process
right
so basically this is the area on the
gene the promoter region that RNA
polymerase will bind
there are things like transcription
factors
that help with this binding
so this is initiation in part one
now for initiation remember that the DNA
is always the template to start this but
only one strand will become or be used
as the template strand to make messenger
RNA
the other strand does not participate at
all
the second part of this is elongation
so think about it we are
making
a long
strand
of RNA
so this is where the RNA polymerase is
actually making
that's what synthesize means making
the RNA
so the RNA polymerase is going to move
along the piece of DNA using
complementary base pairing to do this so
if you remember from DNA replication you
had two enzymes
you had an enzyme called helicase
to unzip
and then you had DNA
polymerase
to make DNA strand
here
the RNA polymerase
does both
it unzips
the strand of DNA and then it does the
base pairing
so he's very efficient
so we do have this base pairing of
nucleotides that come in to make this
new
um strain of
RNA
the third step we have is termination
and if you get terminated from a job
you're basically getting fired so you
stop working there
that's what happens here the RNA will
reach the end
there is a Terminator sequence
that tells
the RNA polymerase
to stop
and once it reaches that end of the gene
it stops it falls off
once that termination happens the
messenger RNA is complete
at that at the Terminator sequence
the RNA the DNA the RNA polymerase they
all separate from each other the DNA
becomes a double helix again
so this the cell is actually produced an
RNA copy of that Gene
now the overall expression of those
genes is going to be what it makes at
the end but the way that DNA in packaged
regulates gene expression
so when eukaryotic cells our cells for
instance Gene regulation actually starts
in the nucleus
some genes are wound up so tight they
can't be transcribed but other genes are
available
and what's cool is once you get that
messenger RNA remember how I said you
can't leave your house until you're
mature
well they're going to go through a
process
that removes pieces of RNA that doesn't
need to be there
and it's going to allow only those
pieces of RNA
to actually leave so if you notice
there's two types there are what called
exons and introns
introns
get removed and stay in
the nucleus
Excellence exit
the nucleus and become what's known as
mature messenger RNA and it's going to
move out of those nuclear pores
to the cytoplasm
and as I also um said about starting
transcription you have or what are known
as transcription factors and they help
to regulate gene expression too
in eukaryotic cells many different
proteins that are called transcription
factors combined to DNA and help with
the process of transcription being
turned on
this is going to affect the activity of
RNA polymerase altering the rate of
transcription
in eukaryotic cells they can use
different combinations of what are
called exons this is what's known as
alternate splicing and this creates
different proteins from the same
messenger RNA
so you can see here the introns get cut
out and stay in
they really get
um deteriorated
and then the exons exit
and they become the actual messenger RNA
that will be translated to a protein
you also have the process of RNA export
that regulates gene expression so
certain eukaryotic proteins can actually
hold messenger RNA inside the nucleus
making it so that it can never reach a
ribosome so that will also determine
whether or not a Gene gets expressed or
made into a protein
ornate degradation can also regulate
gene expression degradation means
breaking down
so when that messenger RNA exits the
nucleus and goes into the cytoplasm
right that's where it is now
some messenger RNA may be broken down to
graded very quickly so they can't be
translated into very much protein or
protein at all other messenger rnas are
long-lived and can be translated into a
lot of protein over time so depending on
your genes it can either
um
be translated for a long time or short
amount of time based on RNA degradation
protein activity can also regulate gene
expression some proteins are more stable
why others are broken down quickly
moreover in order to function proteins
must also be folded properly and reach
the correct location so we were talking
about the Philadelphia in mad cow
disease and as you know and what we'll
talk about later in this talk is an idea
of prions but first in order for us to
understand what a prion is we have to
know what a protein is and how proteins
are made but as I always say for
instance I have a shirt on right now it
has a hole at the top so I can put my
head in it it has two holes so that my
hands and my arms can go through it it
has a large hole at the bottom so my
torso can fit now I could have this
shirt made but if the hole where my head
goes through isn't there
it's not gonna work as a shirt
so if proteins aren't put together
correctly I.E folded right they won't
work right
so this is one important thing that we
will talk about
so let's review transcription really
quick and you can take some important
notes on the things that you feel are
the most important in the process and
remember it is in three steps initiation
elongation
and termination that's how I remembered
them and this will give you an idea of
how this works overall
and this will lead us to
the idea of RNA processing
and basically one more step in order for
the RNA
to leave the nucleus once transcription
is complete
it needs to be processed to become
mature
one of those is the introns and exons
so if you think prokaryotic cells
everything happens in the cytoplasm they
don't have a nucleus
so as once transcription is complete
they will start translating protein now
they can actually have it happen at the
same time as in
the process of transcription could be
happening in as it transcribes the DNA
at the areas that have already been made
to messenger RNA you can start
translation on it's pretty cool but
eukaryotic cells all of this is
happening in the nucleus so there has to
be chemical alterations that happen
before the messenger RNA can actually
leave for a translation to start
and one important process is adding a
cap and a tail to the messenger RNA
so as you notice the five primary that
had that phosphate they're going to add
this little structure that's called the
cap and then on the three prime they're
going to add what's called a poly a tail
and if you remember if you've ever heard
of anything called polyamorous
relationships versus monogamous
relationships monogamous starting with
mono means one
polyamorous means many people in a
relationship so polyatil just means
there's a lot of A's at the end and this
cap and a tail is going to protect the
messenger RNA from being broken down
once it goes into the cytoplasm
also we remove introns and the exons
become the sequence that's going to
specify the amino acids
and the introns are sequences in the
gene that aren't used for producing a
protein
so the introns are removed before it
leaves the nucleus
both of these allow the RNA to be ready
for translation or become mature
this processed RNA is now a functional
messenger RNA molecule
once it's completed that processing it
leaves the nucleus and then it will bind
to a ribosome in the cytoplasm for
translation to begin
and this is where we're going to stop
for this video so that you can
kind of review your notes look at
transcription and when we start here in
a minute we're going to talk about
translation and translation is we finish
this right
and now we're starting this
which is the process of taking messenger
RNA to proteins this is happening in the
cytoplasm in the messenger RNA is the
messenger from the nucleus on how that's
to happen
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