Base Excision Repair | DNA Repair Mechanism
Summary
TLDRThis video delves into the base excision repair mechanism, a crucial single-strand DNA repair process. It explains how enzymes like DNA glycosylase, AP endonuclease, DNA polymerase, and ligase work together to identify and fix base damage caused by chemicals or radiation. The video highlights the transformation of cytosine into uracil and the subsequent risk of point mutations during replication. The detailed mechanism showcases the steps from base recognition and removal to the final sealing of the DNA strand, emphasizing the importance of this repair process in maintaining genetic integrity.
Takeaways
- 🧬 The video discusses base excision repair, a mechanism for fixing single-strand DNA damage.
- 🔍 Damage to DNA bases can occur spontaneously due to exposure to chemicals or radiation, often affecting a single base.
- 🧩 The four DNA bases are adenine (A), thymine (T), guanine (G), and cytosine (C), with single base damage leading to mutations.
- 🛠️ Hydrolytic deamination is a common cause of base damage, transforming cytosine into uracil, which is not a normal DNA base.
- 🧬 Base excision repair involves specific enzymes to identify and repair the damaged bases.
- 🔬 DNA glycosylase is the enzyme that recognizes the damaged base and removes it from the DNA strand.
- ✂️ AP endonuclease then cleaves the DNA at the site where the base has been removed, creating a nick in the phosphodiester backbone.
- 🔄 DNA polymerase fills in the missing base, restoring the DNA strand to its original sequence.
- 🔗 DNA ligase seals the nick in the DNA backbone, completing the repair process.
- 📚 Flap endonuclease, such as PEN-1, is involved in long patch base excision repair, dealing with more extensive damage.
- 🔄 The detailed mechanism shows how base excision repair corrects uracil misincorporation during DNA replication, preventing point mutations.
Q & A
What is the main focus of the video?
-The video focuses on explaining the base excision repair mechanism, which is a single-strand DNA repair process.
Why is base excision repair important for DNA?
-Base excision repair is crucial as it corrects damage to a single DNA strand caused by chemicals or radiation, preventing mutations and maintaining genetic integrity.
What are the common causes of base damage in DNA?
-Base damage in DNA is commonly caused by hydrolytic deamination, oxidation, and alkylation, with hydrolytic deamination being the most pronounced.
How does the base damage transform the normal bases in DNA?
-Base damage can transform cytosine into uracil, adenine into hypoxanthine, and guanine into xanthine, which are abnormal bases not found in normal DNA.
What is the role of DNA glycosylase in the base excision repair process?
-DNA glycosylase recognizes the damaged base and removes it from the DNA strand, initiating the base excision repair process.
What is the function of AP endonuclease in DNA repair?
-AP endonuclease recognizes the abasic site (missing base site) and cleaves it, creating a nick in the phosphodiester backbone, allowing for further repair steps.
How does DNA polymerase contribute to the repair process?
-DNA polymerase inserts the missing base into the DNA strand after the damaged base has been removed, filling the gap left by the excision.
What is the role of DNA ligase in the final step of base excision repair?
-DNA ligase seals the nick in the DNA backbone, completing the repair process and restoring the integrity of the DNA strand.
What is flap endonuclease and when does it act in the repair process?
-Flap endonuclease, in the form of PEN-1, removes the flap structure generated during long patch base excision repair when more than one base is synthesized from an abasic site.
How does the presence of uracil in DNA lead to a point mutation during replication?
-During replication, if a damaged strand with uracil is used as a template, DNA polymerase will incorrectly pair adenine with uracil instead of cytosine, leading to a change in the genetic code and a point mutation.
Why is it necessary to repair uracil in DNA immediately after it is formed?
-Uracil in DNA, if not repaired, will cause errors during replication by leading to incorrect base pairing, which can result in point mutations and genetic disorders.
Outlines
🧬 DNA Base Excision Repair Mechanism
This paragraph delves into the process of base excision repair, a crucial single-strand DNA repair mechanism that rectifies damage caused by chemicals or radiation. It explains how DNA bases can be altered through hydrolytic deamination, oxidation, and alkylation, leading to the formation of abnormal bases like uracil, hypoxanthine, or xanthine. The paragraph outlines the enzymes involved in this repair process, starting with DNA glycosylase, which recognizes and removes the damaged base, followed by AP endonuclease that cleaves the phosphodiester backbone at the abasic site. DNA polymerase fills in the missing base, and DNA ligase seals the nick. The role of flap endonuclease in long-patch base excision repair is also mentioned. The summary highlights the detailed mechanism, starting from the damage caused by the incorporation of uracil during replication, which can lead to point mutations, to the correction of such errors by the base excision repair pathway.
👍 Viewer Engagement and Subscription Call
The second paragraph serves as a call to action for viewers, encouraging them to show their appreciation for the video by liking it and giving it a thumbs up. It also reminds viewers to subscribe to the channel for more content, reinforcing the importance of viewer interaction and subscription for the channel's growth and engagement.
Mindmap
Keywords
💡Base Excision Repair
💡DNA
💡Enzyme
💡Hydrolytic Deamination
💡Adenine, Thymine, Guanine, Cytosine (ATGC)
💡Uracil
💡AP Site
💡DNA Polymerase
💡DNA Ligase
💡Flap Endonuclease
💡Point Mutation
Highlights
The video discusses the base excision repair mechanism for DNA damage, specifically for single-strand DNA repair.
DNA damage can be caused by chemicals or radiation, leading to base modifications such as hydrolytic deamination, oxidation, and alkylation.
Hydrolytic deamination is the most common cause of base damage, transforming cytosine into uracil.
Abnormal bases like uracil, hypoxanthine, and xanthine are not found in normal DNA and can lead to genetic mutations.
Base excision repair is initiated by DNA glycosylase, which recognizes and removes damaged bases.
AP endonuclease recognizes the abasic site and cleaves the phosphodiester backbone.
DNA polymerase inserts the missing base to restore the DNA strand.
Ligase enzyme seals the nick in the DNA strand, completing the repair process.
Flap endonuclease, such as PEN-1, is involved in long patch base excision repair when multiple bases are synthesized.
The video explains the detailed mechanism of base excision repair, starting from DNA damage to the repair process.
Uracil in DNA can cause point mutations during replication if not repaired, as it pairs with adenine instead of guanine.
Uracil DNA glycosylase specifically targets and removes uracil from the DNA molecule, preventing mutations.
The abasic site created by the removal of the damaged base is a critical point for the subsequent steps of repair.
DNA polymerase and DNA ligase work together to fill in the gap and seal the DNA strand.
The video emphasizes the importance of base excision repair in maintaining genetic integrity and preventing mutations.
The process of base excision repair is a crucial single-strand DNA repair mechanism within the cell.
The video concludes with an invitation for viewers to like, subscribe, and support the channel for more informative content.
Transcripts
hello friends in this video we'll be
discussing about the base excision
repair wire damage to DNA is reviewed by
enzyme identity and make sure to note
here that it's a single strand DNA
repair mechanism not a double strand
repair mechanism so here the damage to a
single strand gets repaired we see here
we have a normal DNA molecule present
within the cell and when it gets exposed
to chemicals or additions it
spontaneously damages the bases in a
strand and most of the time we see
single base gets damaged among the four
bases that's ATGC adenine thymine
guanine and cytosine the single base
damage is mediated by hydrolytic
deamination oxidation and alkylation but
hydrolytic domination is more pronounced
order which transforms the bases into
abnormal basis like cytosine adenine and
gowning bases in DNA spontaneously palm
uracil hypo Centene or xanthine
respectively which you will never find
in normal DNA and when this type of
damage is found in the cell the base
excision repair comes into play to
repair the damage now let's have a look
on the enzymes that drive the base
excision repair first of all we have DNA
glycosylase it recognizes the lesion and
remove the damaged base from the strand
then we are AP endonuclease a purine ik
or a pyrimidine and a nucleus depending
upon which base is damaged either it may
be purine or pyrimidine this ap endo
nucleus recognizes the AP side that's a
missing base site and creates sneak in
phosphodiester backbone then we have DNA
polymerase which inserts the missing
base to DNA and finally there ligase
enzyme seals the knee
but we have also another enzyme here
that's called flap endonuclease in the
form of pen one it removes that Phi
prime club generated during long patch
base excision repair
that's when more than one base is being
synthesized from ap site so that time
this flap endonuclease also works in now
let's see the detailed mechanism of base
excision repair when the normal DNA gets
exposed to chemicals and or additions it
damages the DNA and one process is the
hydrolytic termination while the
cytosine base in the Strand changes into
uracil so the chemical damage or the
radiation damage changes this cytosine
based in to uracil now in a DNA molecule
we have uracil instead of cytosine till
now it will not harm the cell or any
process here but during the process of
replication
when this damaged strand having damaged
it base is used as a template strand it
will change the genetic code in the new
DNA the base should be cytosine here and
DNA polymerase will complementary
synthesized gowning but this does not
happen here we have the uracil instead
of cytosine here and for the
complementary base uracil the adenine
will be synthesized it by DNA polymerase
during replication thereby changing the
genetic code and it will cause point
mutation so after having uracil in
strand of DNA it's immediately countered
by the DNA glycosylase that's uracil DNA
glycosylase this and then eliminates
uracil from DNA molecule by cleaving the
N
glycolic bond and initiating the base
excision repair so now we have a DNA
with removed base and the site while
base is missing is termed as ap site
then offer this ap site is recognized it
by AP endonuclease which cleaves the ap
side to yield a three hydroxyl edge
ascent clip
are you deoxyribose phosphate as you can
see in this diagram now wherever why did
DNA strained and this white is to be
filled by the enzyme known as DNA
polymerases and DNA ligase the DNA
polymerase and DNA ligase
finally jumps in wire DNA polymerase
insert the missing base that cytosine
and the NIC is sealed by Danielle I
guess eventually so this is how the base
excision mechanism works in when damage
to DNA is found in the cell in the form
of base damage in single strand I hope
you liked the video if you liked it give
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