Transcription: Synthesis of RNA

Question 1

In lecture it is stated that we need transcription for (roughly) three reasons. Generally speaking what are these reasons?

Answer 1

• To protect DNA (from cytoplasmic event)
• Serve cell’s metaboilc needs (by increasing copies of genome)
• Regulate rate of protein synthesis

Question 2

As it pertains to prokaryotic cells, how many RNA polymerase(s) are present? What is its/their function(s)?

Answer 2

1 single RNA polymerase that transcribes all types of RNA

Question 3

In comparison to prokaryotes, eukaryotes have 3 types of RNA polymerases. What is the function of each one?

Answer 3

RNA polymerase I = synthesizes rRNA

RNA polymerase II = synthesizes mRNA

RNA polymerase III= synthesizes tRNA and 5S rRNA

*all three polymerases have the same mechanism of action but recognize different promoters

Question 4

Define the word gene:

Answer 4

A segment of DNA coding for the expression of RNA

Question 5

Define the word promoter:

Answer 5

A sequence for binding of RNA polymerase

Question 6

What is the orientation of the Template strand during transcription?

Answer 6

Complementary and antiparallel to the coding strand

Question 7

In prokaryotes the promoter sequence is TATAAT otherwise known as what?

Answer 7

The Prinbow box

Question 8

In eukaryotes the promoter sequence is TATA also known as what?

Answer 8

TATA box

Question 9

Elongation (during transcription) stops at the terminatino signal through 2 distinct mechanisms: Rho indepentdent and Rho-dependent. What is the difference between these two mechanisms?

Answer 9

Independent: Where thh formation of the hairpin loop by transcript results in the release of RNA polymerase and transcript from DNA.

Dependent: Where the binding of Rho factor causes the release of polymerase and transcript

Question 10

In bacteria, many protien coding genes are linked together and controlled by a single promoter, this is known as a what?

Answer 10

Operon

Question 11

In prokaryote the absence of a nucleus allows for the combination of what 2 processes?

Answer 11

Transcription and Translation

Question 12

The drug Rifampin is used to treat a TB infection it is a potent inhibitor of what?

Answer 12

Bacterial RNA polymerase

Question 13

In eukaryotes promoters can contain multiple binding sites for General Transcription Factors (GTFs). What is the purpose of GTFs?

Answer 13

They interact with each other and RNA polymerase II to initiate transcription.

Question 14

In the process of synthesizing eukaryotic mRNA, what is the component known for increasing mRNA stability?

Answer 14

Poly A tail (added by poly A polymerase)

Question 15

Splicing requires 3 components: GU nucleotide at one of the intron, a splice acceptor /an AG nucleotide sequence at the opposite end, and a branch point near the splice acceptor. What is the component responsible for recognizing these 3 splice sites?

Answer 15

snRNA’s

Question 16

In lecture we learn about the protein RBM20 which facilitates the shift from fetal cardiac titin to adult cardiac titin. It is noted that adults with a greater amount of fetal titin than adult titin will suffer from dilated cardiomyopathy. What is attributed to this pathology?

Answer 16

Mis-splicing

-if they’re are low levels of RMB20 the titin gene is spliced as the longer springy (pathological) form.

Question 17

In thalassemias it is noted that the mutations in the TATA box will result in a B+ phenotype. What is the relevance of the TATA box and why do we not want mutations here?

Answer 17

TATA is the promoter region for eukaryotic genes (meaning the initiation of their transcription) and therefore a mutation here would reduce the accuracy of the start point of transcription.

-This would result in a dramatic decline in production of the protein of interest

Question 18

In eukaryotic transciption the shine-delgarno - equivalent is synthesized. What is it?

Answer 18

The CAP sequence

-> binds to 40S subunit during translation