Theme 2B

Question 1

What determines an organism’s phenotype?

Answer 1

Cell number, type and function.

Question 2

Where does transcription begin on the DNA strand?

Answer 2

Immediately to the right of the promoter DNA sequence (with TATA box).

Question 3

What are the four primary steps to making RNA molecules?

Answer 3

Initiation, elongation, termination, chromatin remodelling.

Question 4

What are the two types of transcriptional initiation processes?

Answer 4

1. General transcription factors bind to the promoter and then recruits RNA poly II.
2. Transcription activator proteins bind to enhancer regions, distant from the promoter. It loops the DNA in order to bring general transcription factors, mediator complex and RNA poly II together.

Question 5

What are the three types of termination?

Answer 5

1. Rho- independent termination (prokaryotes)
2. Rho- dependent termination (prokaryotes)
3. Cleavage and polyadenylation specificity factor (eukaryotes) (CPSF)

Question 6

What is the definition of epigenetics?

Answer 6

Regulation of gene transcription by posttranslational modification of histones.

Question 7

What are the four aspects of post-transcriptional regulation of gene expression?

Answer 7

1. 5’ Capping
2. 3’ Polyadenylation
3. Splicing
4. MicroRNAs

Question 8

What part of amino acid tail of histones affects transcription of genes?

Answer 8

Lysines.

Question 9

How are lysines affected?

Answer 9

1. Histone acetyltransferase (HATs) that add acetyl groups (CH3CO- to histone tails increase gene transcription by loosening DNA binding.
2. Methylation of histone tails can activate (Me) and repress (Me3) transcription of genes.

Question 10

What is the donor splice site?

Answer 10

The part that gets spliced initially by spliceosome to form a loop.

Question 11

What is it called when you splice to create different proteins from the same gene?

Answer 11

Alternative splicing.

Question 12

What is microRNA transcribed by?

Answer 12

RNA poly II.

Question 13

What are the double stranded miRNA/siRNA substrates of?

Answer 13

RISC (RNA induced silencing complex).

Question 14

How does RISC work? 2 steps.

Answer 14

1. RISC unwinds one of the RNA strands which attracts binding of the complementary RNA
2. Binding of the mRNA to RISC interferes with translation initiation (miRNA) or induces mRNA degradation (SiRNA)(represses gene expression posttranscriptionally).

Question 15

What is a possibility of why RISC was created?

Answer 15

For an antiviral mechanism against viral mRNA.