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.
Пікірлер: 103
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
@hussainbiology
Ай бұрын
glad to know that...
Thank you for this CLEAR explanation!
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.
excellent explantion! Thanks so much
Thank you for this through explanation!
thank you! super helpful and clear!
THANKS HUSSAINNN !!! YOU ARE THE BEST !
@hussainbiology
5 жыл бұрын
Thanks Emila for appreciation...Glad to know that it helps.....
Always been a big fan of your work.... Can you please do a video on Nucleotide excision repair?
very well done mate
Video excellent bro,but voice is not clarity,make sure for that
Great work ... Keep it up...
Thank you so much!!
Good one . Thanks
Thanks for precise and clear explanation 🙏
@hussainbiology
3 жыл бұрын
You are welcome ✌️
great explanation
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 :)
@hussainbiology
6 жыл бұрын
Glad to know that my work helps you and i really appreciate your words ........It really boosts my confidence ..... Thanks Ayesha 😊
Superb explanation
fantastic video, thank you :0)
@hussainbiology
4 жыл бұрын
you are welcome ✌️
Amazingly explained
@hussainbiology
5 жыл бұрын
Thanks Pranali for appreciation...Glad to know that it helps...
I learned that from your one previous video
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 ✨
@hussainbiology
Жыл бұрын
thanks for appreciating my work.... keep sharing
WONDERFUL!!
@hussainbiology
5 жыл бұрын
Thanks dear for appreciation
T hank you
This video is awesome!
@hussainbiology
6 жыл бұрын
Thanks Sarah for appreciation.....Keep supporting 😊
Because of methylated cytosine converts to thymine by removing amino group and adding one h2o molecule
Vedio was helpful
Thank u
@hussainbiology
5 жыл бұрын
Thanks buddy for appreciation....
U r doing great...keep it up
@hussainbiology
Жыл бұрын
Thank you so much 😀
good !
@hussainbiology
6 жыл бұрын
Thanks Buddy....appreciate ur support
Nice nice very nice
@hussainbiology
5 жыл бұрын
Thanks Mansha for appreciation...
Thanku sir🥰
@hussainbiology
Жыл бұрын
my pleasure... Glad it helps ✌️
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?
replication, transcription and translation
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
@hussainbiology
2 жыл бұрын
Great 👍 first of all thanks buddy for appreciation .... and where from u got to know i am from Kashmir ?
@beighmubashir4902
2 жыл бұрын
@@hussainbiology comment sections se pata chala bhai ...thanks to you I almost topped my batch after watching your vedios ..
Plz recombination repair topic pr video bnado sir..🙏🙏🙏
@hussainbiology
Жыл бұрын
Haan jaldi
Do we have a short-patch and long-patch repair in prokaryots ? Is it kinda BER ?
@hussainbiology
9 ай бұрын
Yeah….it is kinda a BER
do you provide any notes in any ur website or in pdf format...it will be really helpful!!!
@hussainbiology
3 жыл бұрын
Apologies.. the website is not functional anymore and as of now I don't provide any notes
@MelomaniacEarth
3 жыл бұрын
@@hussainbiology its fine sir...the video itself was informative 🙂
base excision what 😳
Sr nucleotide repair ki video kb banaoge 2 sal ho gai
❤❤
👏🏻👏🏻👏🏻
Sir u don't have nucleotide excision repair lecture video i need this
@hussainbiology
6 жыл бұрын
Apologies.... I haven't made a video on that yet but i will definitely consider your suggestion .
@hemjoshi1724
6 жыл бұрын
Hussain Biology sir is it possible tomorrow because I have exam ur previous lectures helped me in understanding the topic so I need for this also if possible
@hussainbiology
6 жыл бұрын
Sorry Hem.......It is not possible to make a video and edit it within few hours...
@hemjoshi1724
6 жыл бұрын
Hussain Biology ok sir
@hussainbiology
6 жыл бұрын
Apologies,,,,,Couldn't help
You didn't clearly explain the work of Ap endonuclease. DNA glycosylase removed the base... And what did the Ap endonuclease do?
@FOODIESWITHAQSA
3 жыл бұрын
AP endonuclease cut phosphate sugar backbone and create a nick
@bibek8945
3 жыл бұрын
@@FOODIESWITHAQSA now i get it... Tq
Sir wil u plz make a video on reversion mutation?...it is complicatd, evn im nt undrstng why reversions r used to tst mutagenicity.... plz sir make me clear?😊
@hussainbiology
6 жыл бұрын
I will definitely help you out.......
@Micro-life
6 жыл бұрын
Hussain Biology ...advance thnks sir😊😊😊
@Micro-life
6 жыл бұрын
Hussain Biology ...thnku sir fo sharing😊😊😊😊
@hussainbiology
6 жыл бұрын
My pleasure 😊😊😊😊
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???🥺
@hussainbiology
Жыл бұрын
No no.. i don't think i have made a video on that topic..... Ya toa mai he bhool gaya hoon
Where is nucleotide excision repair???
sir kya apki videos NET k liye b usefull hoti hain...?
@hussainbiology
6 жыл бұрын
Hi Navita.......Yes i try to make advanced level videos and I hope you will find them useful for CSIR net.... My Channel is totally based on CSIR NET.....
@navitahooda6427
6 жыл бұрын
Hussain Biology thanq sir
@hussainbiology
6 жыл бұрын
You are welcome.....
sorry what is AP Site?
@hussainbiology
5 жыл бұрын
apurinic or apyrimidinic site. Where Purine or Pyrimidine is missing.
@ComandaKronikk
5 жыл бұрын
@@hussainbiology I've been told by my professor that AP sites are strictly for missing purines
@hussainbiology
5 жыл бұрын
@@ComandaKronikk Actually apyrimidine site is very rare since it requires high acidity to cleave off the pyrimidine from the site where as Apurine site is easily formed in the cell at lower acidity or even under neutral pH. that is why your Professor has told u it is mostly Purines.
I think the hydrolytic deamination results in cytosine to thymine not uracil
you are from kashmir? I can tell from your sound..lol😁
@hussainbiology
5 жыл бұрын
Indeed i am Kashmiri...
@basharatali927
5 жыл бұрын
which district? srinagar?
@hussainbiology
5 жыл бұрын
@@basharatali927 Baramulla Pattan
@basharatali927
5 жыл бұрын
ok sir BTW I am a sheena dard from Gurez valley bandipora ..
@hussainbiology
5 жыл бұрын
That is great......Means i have now subscriber from Gurez also...,😊😊
It's not gounine it's guanine.... correct the pronunciation Mr. 🙂
@hussainbiology
23 күн бұрын
Apologies....i accept i am bad at pronunciation but the point is... u understood still
Plz teaches in Hindi
your pronounciation is a bit of. You pronounce repair as rapier. Good pronounciation is like r eee p eehhhhh r.
@karishmadeegan8297
3 жыл бұрын
90 percent of his audience is Indian so I don't think pronunciation is a major concern for him. Yes it is slightly off but it doesn't need to be perfect. It's still understandable for most of his viewers :)
@janhavikuvar173
2 ай бұрын
Tere se pucha??
@Snaomib
Ай бұрын
L take
Video excellent bro,but voice is not clarity,make sure for that