Biochemistry 3 | بايوكمستري 3
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تسجيلات الكلية ...
والشيتات علي هيئة بي دي أف ...
ومواعيد المحاضرات ....
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اسئلة د.محمد القرقوري ف جزئية الجين والانزيمولوجي👆

اسئلة مفاضلة 2 السيم اللي فات
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ملاحظات د. عبد الله بشين في المحاضرة الأولى * Regulation of Gene Ex. *

- Each cell expresses particular genes; therefore, each cell has its own morphological and functional characteristics.

- Insulin gene: found in all cells but only expressed in Beta cells of pancreas.

- Constitutive genes are expressed in all types of cells.
e.g. enzymes for glycolysis

- DNA is not converted to RNA, it is only photocopied. *used as a template to synthesize RNA*

- Proteins, RNA, carbs can't act as a template.
Except in reverse transcriptase of retroviruses which uses an RNA as a template to transcribe a DNA segment in a process called reverse transcription.
Telomerases can use RNAs to synthesize nucleotide sequences in the DNA as well.

- Types of DNA:
cDNA "Complementary DNA"
Genomic DNA (found in nucleus)
Mitochondrial DNA

- Unicellular organisms are affected faster by the external environment than multicellular organisms.

- At temperatures: 25-37 degrees Celsius, yeast will produce heat-shock proteins to adapt to the new environment.

- Operons are found in prokaryotes.
Polycistronic mRNA is found in prokaryotes.

- Monocistronic mRNA found in both.

- LacI is a constitutive gene which is continuously expressed at low* rates. (Has a weak promoter: sequence for attachment of factors is far from the consensus seq.)

- The area between the start and stop codons in the mRNA *the translated area* is known as: Open-reading frame.

- Prokaryotes don't have a nucleus, so both transcription and translation happen in the cytosol. Translation can start before transcription ends.

- In eukaryotes transcription and translation are separated both in time and location. So gene expression is a lot slower in eukaryotes.

- Post-transcriptional modification *adding CAP and Poly-A tail* happens only in eykaryotes and is another reason why Gene Ex. is slower in eukaryotes.

- Haematopoietic stem cells divide rapidly, so they express genes responsible for the cell cycle at very high rates. "Proto-oncogenes"

- Proto-oncogenes: genes expressed in haem. cells to speed up cellular proliferation.

- The mature** cell will not express these genes.

- Tumor suppressor genes: stop cellular proliferation.

- Leukemia: cells don't achieve maturity *they replicate non-stop*.