Control of gene expression

Question 1

Why is gene regulation necessary?

Answer 1

Regulate enzyme + hormone production

Question 2

How is gene expression controlled at the transcriptional level?

Answer 2

Chromatin remodelling

Histone modification

Question 3

Describe chromatin remodelling?

Answer 3

—> DNA wrapped around histones = chromatin

Transcription cannot occur when DNA tightly wound as RNA polymerase cannot access genes.

Protein synthesis only occurs during interphase.

Question 4

How does chromatin remodelling ensure regulation?

Answer 4

Ensures proteins necessary for cell division synthesised in time.

Prevents complex/energy-consuming protein synthesis from occurring when cell is dividing.

Question 5

Describe histone modification?

Answer 5

DNA -

Histones +

.: DNA coils around histones

Histones modified to increase/decrease degree of packing.

Question 6

What does epigenetics refer to?

Answer 6

Describes control of gene expression by modification of DNA.

Question 6

How is gene expression controlled at the post-transcriptional level?

Answer 6

RNA splicing

RNA editing

Question 7

Describe RNA splicing?

Answer 7

Primary mRNA = Mature mRNA

Introns removed + exons joined together

Modified nucleotide added to 5’ end.

Long chain of adenine nucleotides added to 3’ end.

Help stabilise mRNA

Question 8

Describe RNA editing?

Answer 8

Sequence of mRNA molecules change through addition, deletion, substitution.

Result in synthesis of different proteins = different functions

Increases range of proteins made from single mRNA molecule.

Question 9

How is gene expression regulated at translational level?

Answer 9

Degradation of mRNA

Binding inhibitory proteins to mRNA

Activation of initiation factors

Question 10

What are protein kinases?

Answer 10

Enzymes which catalyse addition of phosphate groups to proteins.

Changes tertiary structure .: function of protein

Important regulators of cell activity

Often activated by cAMP.