Genetic Expression

Question 1

Suggest how a mutation van lead to the production of a protein that has one amino acid missing

Answer 1

A loss of a triplet

So that amino acids is not coded into the polypeptide sequence

Question 2

Suggest how the production of a protein wih one major and missing may lead to a genetic disorder such as Ellis -van Creveld syndrome

Answer 2

It changes the positioning of bonds of ionic, disulfide and hydrogen bonds in the tertiary structure

This results in a different active site and so afaukty enzyme

Question 3

Suggets how molecules such as oestrogen can effect gene expression

Answer 3

It binds to the protomer which it stimulates

RNA polymerase binds to the the start of the target gene and increases transcription

Question 4

what is cancer

Answer 4

cancer is the result of cell multiplication/ replication that is out of control

Question 5

doctors have found that cancer of the larynx is associated with high levels of tobacco use

Describe one type of evidence that could led them to make the association

Answer 5

1. positive correlation between the amount of tobacco used and cases of cancer of the larynx

Question 6

The scientists found that the protomer DNA of the p16 gene had become methylated

The protomer in the sequence of bases where the enzyme RNA - polymerase binds a DNA molecule

Explain how methylation of the protomer sequence of the p16 gene could cause changes shown in figure 5

(Figure 5 shows the amount of p16 protein decreasing against time exposed to cadmium ions)

Answer 6

methyl groups bind to DNA and so p16 can not be transcribed/ expressed

RNA polymerase could not bind to DNA so no transcription of the gene

Question 7

peroxides are chemicals that can cause changes in DNA

Ebesien reacts with peroxides and breaks them down

Use the information and information from the graph to suggest how oestrogen may increase the risk of breast cancer

Answer 7

1. oestrogen may lead to peroxide formation

2. peroxide affects tumour suppressor gene/ oncogenes

Question 8

how do mutations in the tumour suppressor gene lead to cancer

Answer 8

tumour genes are inactivated

so they are unable to control cell division resulting in cell division to be out of control

Question 9

what does oestrogen bind to

Answer 9

oestrogen binds to a protein, not DNA

Question 10

Explain how increased methylation can lead to cancer

Answer 10

1. Methyl groups are added to (both copies) of the tumour suppressor gene
2. this prevents the transcription of the tumour suppressor gene
3. therefore the protein that the gene codes for is not produced
4. so the cell divides uncontrollably resulting in cancer

Question 11

Suggest and explain two reasons why there is a high frequency of the E280A mutation in Yaramul (lines 13–15)

Answer 11

1. Isolated so inbreeding/ low genetic diversity / small gene pool;
2. Allele inherited (through generations) from a (common) ancestor

Question 12

The age at which the E280A mutation is expressed to cause AD can vary (lines 11–12).

Suggest and explain one reason for this.

Answer 12

1. Epigenetics/environment / named factor e.g. stress, alcohol, toxins, diet, exercise, smoking;
2. methylation (of genes)ORacetylation (of histones);

Question 13

suggest two harms to using stem cells to treat/ replace damaged cells

Answer 13

1. the stem cells might differentiate into the wrong specialised cells
2. the stem cell might divide out of control leading to cancer