Base Excision Repair | DNA Repair Mechanism

The Base excision repair (BER) is a cellular mechanism that repairs damaged DNA throughout the cell cycle. It is responsible primarily for removing small, non-helix-distorting base lesions from the genome. The related nucleotide excision repair pathway repairs bulky helix-distorting lesions. BER is important for removing damaged bases that could otherwise cause mutations by mispairing or lead to breaks in DNA during replication. BER is initiated by DNA glycosylases, which recognize and remove specific damaged or inappropriate bases, forming AP sites. These are then cleaved by an AP endonuclease. The resulting single-strand break can then be processed by either short-patch (where a single nucleotide is replaced) or long-patch BER .

The Base Excision repair mechanism makes use of the following enzymes to repair the DNA :
DNA Glycosylase
AP Endonuclease
DNA Polymerase
DNA Ligase

The Base Excision Repair , is initiated by the damaged DNA due to chemicals and radiations.The Base Excision repair is a single strand repair mechanism where single base gets transformed into different base like in Hydrolytic Deamination where Cytosine changes into Uracil thereby changing the genetic code.

Single bases in DNA can be chemically damaged by a variety of mechanisms, the most common ones being deamination, oxidation, and alkylation. These modifications can affect the ability of the base to hydrogen-bond, resulting in incorrect base-pairing, and, as a consequence, mutations in the DNA. For example, incorporation of adenine across from 8-oxoguanine (right) during DNA replication causes a G:C base pair to be mutated to T:A. Other examples of base lesions repaired by BER include:

Oxidized bases: 8-oxoguanine, 2,6-diamino-4-hydroxy-5-formamidopyrimidine (FapyG, FapyA)
Alkylated bases: 3-methyladenine, 7-methylguanosine
Deaminated bases: hypoxanthine formed from deamination of adenine. Xanthine formed from deamination of guanine. (Thymidine products following deamination of 5-methylcytosine are more difficult to recognize, but can be repaired by mismatch-specific glycosylases)
Uracil inappropriately incorporated in DNA or formed by deamination of cytosine[2]
In addition to base lesions, the downstream steps of BER are also utilized to repair single-strand breaks.

[spicytuna]

oh my God.
i am from non-biology background.
cannot believe our human has this jaw opening cellular dna mechanism.
amazing how this was even discovered.
thank you

[caterine]

THANKS HUSSAINNN !!! YOU ARE THE BEST !

[xzunvqm]

Thank you for this through explanation!

[yazanabandah]

Ap Endonuclease cleaves the 5’ end .. and Lyase cleaves the 3’ end .. then DNA polymerase and DNA lygase play role.
You forgot to mention the Lyase part!
“Base-specific Glycosylase removes altered base and creates AP site (apurinic/apyrimidinic). One or more nucleotides are removed by AP-Endonuclease, which cleaves the 5′ end. Lyase cleaves the 3′ end. DNA Polymerase-β fills the gap and DNA Ligase seals it. Occurs throughout cell cycle.” GEL PLease! (The steps gylcosylase, endonuclease, lyase, polymerase, ligase)
The quote is from FA USMLE step 1, biochemistry section (2 section), page 40.

[namratagupta]

Thanks for precise and clear explanation 🙏

[smahi]

Always been a big fan of your work.... Can you please do a video on Nucleotide excision repair?

[ayeshahameed]

i just want you to know that all of your videos are awesome... keep it up... and help us by making more clear videos like that :)

[keerthichandranchoutapalli]

Your videos helps me a lot during my exams and makes easy to understand the topics short and very clear.. I really appreciates your hard work... Keep it up... Try to make videos in regarding to every concept in biology because some hard portions we are finding your videos... Once again thank you for your great work ✨

[asankhadiptoghosh]

I learned that from your one previous video

[kannankamal]

Video excellent bro, but voice is not clarity, make sure for that

[asankhadiptoghosh]

Because of methylated cytosine converts to thymine by removing amino group and adding one h2o molecule

[JS-hhzs]

One question though. How the DNA glycosylase know which base (in this case uracil), are the wrong uracil. After all, there are uracil also in immature mRNA. Why don't the glycosylase also cut the uracil from the right nucleotide? how it recognize the wrong uracil?

[elahefa]

Do we have a short-patch and long-patch repair in prokaryots ? Is it kinda BER ?

[Thewiseenigma]

Sr nucleotide repair ki video kb banaoge 2 sal ho gai

[srimanc.r]

replication, transcription and translation

[MelomaniacEarth]

do you provide any notes in any ur website or in pdf format...it will be really helpful!!!

[yashusharma]

Plz recombination repair topic pr video bnado sir..🙏🙏🙏

[beighmubashir]

Today I got to know that u r from Kashmir...I was thinking that u r Pakistani, , ...I am from lolab valley kupwara and I am studying outside state and your vedios has helped me a lot from previous few years....Love u bro and now I am much proud on myself that whatever I achieved, some credit goes to u also ....Love u man 😊...proud of uhh

[bijayachettri]

Sir you've deleted video on nucleotide excision repair ??? It was in your channel and i couldn't find it ..will you let me know you deleted or its there???🥺

[hemjoshi]

Sir u don't have nucleotide excision repair lecture video i need this