Gene Expression

Question 1

What process copies DNA to mRNA?

Answer 1

Transcription

Question 2

Where does transcription occur?

Answer 2

In the nucleus

Question 3

What process converts mRNA to proteins?

Answer 3

Translation

Question 4

Where does translation occur?

Answer 4

In the cytoplasm.

Question 5

What are the three stages of transcription and translation?

Answer 5

Initiation, elongation, termination.

Question 6

During DNA replication, name the enzyme, substrate and template used.

Answer 6

Enzyme - DNA polymerase
Substrate - dNTPs
Template - DNA

Question 7

During transcription, name the enzyme, substrate, and template used.

Answer 7

Enzyme - RNA polymerase
Substrate - NTPs
Template - DNA

Question 8

During translation, name the enzyme, substrate and template used.

Answer 8

Enzyme - ribosome
Substrate - amino acids
Template - mRNA

Question 9

What is the name of the promoter sequence used to indicate transcription?

Answer 9

A TATA box (TATAAA)

Question 10

Does the TATA box exist on the coding strand or the template strand?

Answer 10

Coding strand
The code ATATTT exists on the template strand and the complimentary code TATAAA on the coding strand initiates transcription.

Question 11

Does the template strand run 5’ to 3’ or 3’ to 5’? What does that make the coding strand?

Answer 11

Template strand - 5’ to 3’

Coding strand - 3’ to 5’

Question 12

What does rRNA stand for?

Answer 12

Ribosomal RNA

Question 13

What does mRNA stand for?

Answer 13

Messenger RNA

Question 14

What does tRNA stand for?

Answer 14

Transfer RNA

Question 15

What are the names of the capping systems used at the 5’ end and the 3’ end of the complete mRNA strand after transcription?

Answer 15

5’ - a 5’ cap

3’ - a polyA tail followed by the sequence AAAAA… until ten 3’ termination end.

Question 16

What does capping do?

Answer 16

Give protection and stop degradation.

Question 17

What happens to pre-mRNA to make the complete mRNA strand?

Answer 17

The introns are spliced from the pre-mRNA to create a shorter mRNA strand of exons.

Question 18

What codons ALWAYS starts translation and what bases is it made up of?

Answer 18

Methionine
A - Alanine
U - Uracil
G - Guanine

Question 19

How are the complimentary bases on a tRNA stem loop bonded?

Answer 19

Through hydrogen bonds

Question 20

What is an anticodon?

Answer 20

An anticodon on a tRNA molecule which is complementary to the codon on the mRNA strand. An anticodon lies at the bottom of the stem loop of tRNA and codes for a specific amino acid.

Question 21

What is tRNA’s function?

Answer 21

TRNA is a molecule that transfers amino acids from the nucleus to the ribosome for protein synthesis.

Question 22

What is the shine-dalgarno sequence?

Answer 22

The coding sequence where the ribosome joins the strand, located about 8 bases up from start codon. Translation does not begin at this point. There a short sequence of non-coding region before the start codon begins coding.

Question 23

What do E, P and A regions stand for and where are they located?

Answer 23

E = E side, this is the left hand side of the start codon at the beginning of translation.
P = Peptidyl site, on the start codon, in the middle.
A = Aminoacyl site, to the right of the start codon, the next codon to be coded.

Question 24

In translation, what happens in elongation?

Answer 24

A peptide bond is created between the amino acid coded on the P site and and the amino acid on the A site. The ribosome then moves from left to right (5’ to 3’), so the original P position is taken up by E, A by P and A is a new codon. As the ribosomes moves along the strand a polypeptide chain is created with the amino acids coded in translation, creating a protein.