Transcription

Question 1

During transcription, is the entire genome transcribed?

Answer 1

No, only the genes that are needed.

Question 2

During transcription, is the DNA strand read from the 3’ end or the 5’ end?

Answer 2

3’ to 5’

Question 3

Are genes more dense in eukaryotic or prokaryotic DNA?

Answer 3

Prokaryotic DNA

Question 4

Is all of the DNA that is transcribed also translated?

Answer 4

Yes in prokaryotes No in eukaryotes as introns are removed.

Question 5

What is the difference between location of related genes in eukaryotes and prokaryotes?

Answer 5

In prokaryotes related genes are located near each other. In eukaryotes, related genes can be on different chromosomes.

Question 6

What enzyme catalyses transcription?

Answer 6

RNA polymerase.

Question 7

During transcription, how many phosphate groups are present on incoming ribonucleotides? What changes are made to the phosphate groups?

Answer 7

Nucleotides come in with triphosphate groups (ribonuceloside triphosphates). Cleavage occurs between the first and second phosphate groups, leaving one on the nucleotide. The released energy is used for RNA synthesis.

Question 8

What is the rate of transcription?

Answer 8

20nt/second

Question 9

In the image shown in which direction is transcription occurring? (Show are short RNA strands coming off the left end of the DNA and long RNA strands coming off the right side of DNA)

Answer 9

Left to right.

Question 10

What is a-amanitin?

Answer 10

A drug produced by some mushrooms that inhibit the active site of RNA polymerase. Highly toxic and primarily affects the liver which is highly active.

Question 11

Why can transcription and translation be coupled in prokaryotes but not in eukaryotes?

Answer 11

Prokaryotes have no nucleus.

In eukaryotes, transcription occurs in the nucleus while translation occurs in the cytosol.

Question 12

From which end is RNA read during translation?

Answer 12

5’ to 3’

Question 13

Why is eukaryotic transcription more complicated than in eukaryotes?

Answer 13

• Genes interupted by non-coding sequences
• Chromatin structure/protein association
• Multiple polymerases
• Compartmentalisation means that RNA must have a prolonged half life.

Question 14

By convention, what is used to label introns and exons?

Answer 14

Introns are labelled with letters, while exons are labelled with numbers.