MCGB - Gene Expression

Question 1

What is the name given to the transformation of DNA to mRNA?

Answer 1

Transcription

Question 2

What is the name given to the transformation of mRNA to proteins?

Answer 2

Translation

Question 3

What is a gene?

Answer 3

A stretch of DNA with a chromosomal locus, sometimes also referred to as a unit of inheritance/transcription.

Question 4

Where is the info for where to initiate/terminate transcription and translation stored?

Answer 4

In the genes.

Question 5

Is a ribosome required for making RNA?

Answer 5

No, it is required for making a polypeptide.

Question 6

What are the three stages of making a polypeptide from DNA called?

Answer 6

Initiation, elongation, termination.

Question 7

Describe the three stages of DNA replication (initiation, elongation, termination).

Answer 7

I - recognition of the origin of replication.
E - DNA polymerase extends the strand in the 5’ to 3’ direction.
T - replication forks meet

Question 8

Describe the three stages of transcription.

Answer 8

I - the promoter is recognised by the transcription factor
E - 5’ to 3’ chain growth
T - This is sequence dependent

Question 9

What is a “promoter”?

Answer 9

A region of DNA that initiates transcription of a particular gene.

Question 10

What is a TATA box?

Answer 10

A section of DNA in the promoter region that the transcription factor binds to, which causes transcription to start.

Question 11

Does transcription travel towards or away from the promoter?

Answer 11

Away, and always the same direction on the same gene.

Question 12

In what two ways is mRNA protected from degradation by exonucleases and other enzymes?

Answer 12

CAPPING (an altered base at the 5’ end) and TAILING (also called polyadenylation, lots of A bases are added to the end)

Question 13

What does splicing remove from pre-mRNA?

Answer 13

It removes the introns as they do not code for proteins.

Question 14

DNA is very stable. Why is RNA required to be less stable?

Answer 14

It must be able to be degraded when it is finished with.

Question 15

What is a polyribosome (or polysome)?

Answer 15

A complex of an mRNA molecule and two or more ribosomes that is formed during active translation.

Question 16

Which organelle is formed from rRNA and protein?

Answer 16

Ribosomes

Question 17

What are the five kinds of RNA?

Answer 17

Ribosomal RNA (rRNA), messenger RNA (mRNA), transfer RNA (tRNA), microRNA (miRNA), noncoding RNA

Question 18

Which type of RNA makes up roughly 80% of all RNA?

Answer 18

rRNA

Question 19

Which type of RNA has 100,000s of versions but only a few copies of each?

Answer 19

Messenger RNA

Question 20

What is meant by the statement that the genetic code is “comma-less”?

Answer 20

It has no gaps (and is non-overlapping)

Question 21

Why are there short sections of identical code at the start and end of almost every protein (what do they do)?

Answer 21

They are start and stop codes

Question 22

What is a “stem loop”?

Answer 22

This occurs when a section of RNA folds around and hydrogen bonds are formed between anti-parallel, complementary sequences.

Question 23

What is inosine?

Answer 23

A nucleoside that is formed when hypoxanthine is attached to a ribose ring.

Question 24

Explain the “wobble base pair”.

Answer 24

Due to the degeneracy of the genetic code (different codons code for same amino acid) the third base in the codon has slightly less strict base pairing rules and will form bonds with different bases (eg G can pair with U).