Week 1 - Thursday 6th October

Question 1

List the types of disease causing mutations.

Answer 1

Loss of function mutations - involve a reduction or complete loss of function of the gene product.
Gain of function mutations - can be beneficial but can also result in a non-beneficial gene product, excess production of the gene product or a functionally altered gene product.

Question 2

What is Polymerase eta. (POLH)?

Answer 2

Specialised DNA polymerase which is able to bypass certain blocking lesions (eg. it can accurately bypass UV induced dimers).

Question 3

How is the transcription of genes regulated?

Answer 3

Chromatin modification
* Genes in highly compacted chromatin are generally not transcribed.
* Histone acetylation looses chromatin structure, enhancing transcription.
* DNA methylation generall reduces transcription.
Regulation of transcription initiation
- DNA control elements in enhancers bind specific transcription factors.
- Binding of the DNA enables activators to contact proteins of the promoter, initiating transcription.

Question 4

What is the slippage mispairing mechanism?

Answer 4

During replication, the DNA polymerase and newly synthesised DNA strand complex sometimes temporarily dissociates from the template DNA. In areas with repetitive sequences, the polymerase may reassociate with the template strand in a position one or two repeats ahead or behind where it left off.

Question 5

What is unequal crossover?

Answer 5

Unequal crossover is also referred to as illegitimate recombination, and is a crossover of homologous recombinants that have not been perfectly aligned and so can cause copy number variants (CNV’s).

Question 6

What does ‘nonsynonymous’ mean?

Answer 6

Alters the amino acid sequence of a protein