tutorial qs

Question 1

In which of the following growth media would you expect to see high levels of mRNA synthesis for the
enzymes of the E. coli lac operon?

Answer 1

No glucose, high lactose

Question 2

lactose will only be metabolized if

Answer 2

glucose is absent

Question 3

9. Describe the process of translation termination.

Answer 3

1. When a stop codon is encountered, proteins known as release factors bind
2. The peptide is transferred to a molecule of water (instead of another amino acid) causing the
   peptide chain to be released
3. The ribosome dissociates

Question 4

10. What are the 3 main differences in how bacteria undergo translation?

Answer 4

1. mRNA has no 5’ cap so instead the small ribosomal subunit recognizes a sequence known as the
   Shine-Dalgarno sequence which lies upstream of the start codon
2. Bacteria has polycistronic mRNA
3. Translation occurs in the same place as transcription/replication for bacteria

Question 5

A missense mutation is

Answer 5

a type of base pair substitution that leads to a change from one amino acid to a different amino acid

Question 6

a nonsense mutation is

Answer 6

a type of base pair substitution that leads to a change from one amino acid to a stop codon

Question 7

operons

Answer 7

Contain a cluster of genes transcribed as a single mRNA

Question 8

lac repressor binds when

Answer 8

lactose is present in the cell