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heme abd albari .pdf

تفريغ أول ثلاث محاضرات د.أحمد زايد Gene Expression.

المحاضرة الرابعة من الجين

lecture4
DNA repair:

-if there's mispair (one or more than one nucleotide(either base ,or the whole nucleotide), and this happened each day in one cell about a million mismatch escape the proofreading property of DNA polymerase.
_agents which cause mutations or alteration could be
endogenous(mainly by replication system mispair)
exogenous(by radiation,chemicals,UV light,free radicals....etc)
_ newly synthesized strands aren't methylated,so this is use to identify ,and diffrentiate b\w them and parental strand(v.imp).
-excinuclease v.imp identify and excise the dimers by UV specific endonuclease.
-xeroderma pigmentosum v.imp
_correction of base alteration :
cytosine is deaminated to uracil by nitrous oxide,there will removal of base(uracil)by uracil N glycosylase(can recognize ) and Apyrimidinic site is formed,then apyrimidinic endonuclease will cut the strand ,so the lyase will cut in order for DNA poly can work and ligase will seal both parts of the strand.
_repair of ds. breaks :
those breaks caused by radiation and free radicals or gene rearragements.
-house keeping genes breaks is lethal
-high eupkaryotes(plants and animals)
-lower euokaryotes(monocellualar ,fungi ,viruces,algae)
-there's no repair in transcription
RNA is single strand of ribonucleac acid
functions of different RNA are imp
DNA mutation is replicated b\c genetic material of DNA is preserved as it is.
and,this will result may may be in producing supraactive enzyme or non functioning one.
in 5 prime of mRNA there's a cap(protect from exonucleases)and it's consists of methyl guanosine triposhpate,and recognition
in 3 prime ther's poly A tail also protect from exonuclease actitvity.
rRNA is part of ribosomes(rRNA+proteins)
tRNA transfer of A.As and contain anticodon that recognize the seqense of nucleotide in order to put the right A.As on

المحاضرة الخامسة من الجين ركزوا ع الرسمات!

lecture 5
mRNA production occur in nucleus,but it's function in ribosomes and it's giuded by special eupkaryotic str. that exist in the 5 prime end a chemical str. called cap and it exist for two purposes:
(protection\recognetion).
Genome : all DNA that is present in organism
the number of nucleotides(bp): it's not proportional to number of genes ,it doesn't mean that the more chr. the more the number of genes .
there's no different in gens b\w human (healthy individuals)
-gene expression=transcription+translation(in case of protein only)
because for example tRNA ,rRNA,and snRNA are only transcribed.
-RNA polymerase synthesize the RNA strand in direction of 5prime to 3 prime
-promotor is never transcribed(receive receptor hormone complex ,and regulate the process)
-the genes and promoters are the same in each cell for the same gene ,but what make the promoter start a transcription of same genes differntly is the transcription factors and acticvators
-holoenzyme:is very imp. recognize promoter region.
-difference b\w replication &transcription is very imp.

ملاحظات المحاضرة الاخيرة للدكتور أحمد زايد: ما قالش هلبا حاجات
1- The step with the highest rate of errors during protein synthesis is: the elongation step.

2- Peptidyltransferase is a ribozyme (part of the 23s/28s rRNA) NOT A PROTEIN

3- During Translation the a.a. are added from the COOH end
(The end that is attached to the 3' end of tRNA)

4- Chaperones are important for the folding of large** proteins not small ones.

5- Some genetic diseases are due to incorrect signal*** peptides (The a.a. seq that are responsible for protein targeting)

6- ما قالهاش الدكتور لكن هكي حسيتها مهمة+ نبي نتفكرها 🐣
Translation can be inhibited by the phosphorylation of eIF-2 which inactivates the factor.

7- eIF-2-GTP Factor & others in eukaryotes (IF-2-GTP in prokaryotes) is responsible for the recognition of the initial*** aminoacyl tRNA
*Which will be placed directly in the P site*

8- tRNA attaches to the a.a. by its 3' end

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