up to genome projects

Question 1

explain how a single base substiution causes a change in the structure of a polypeptide (3)

Answer 1

1. changes primary structure
2. changes tertiary structure
3. change in hydrogen/ionic bonds

Question 2

describe how alterations to tumour suppressor genes can leads to the development of tumours (4)

Answer 2

1. increased methylation of TSG
2. mutation in the TSG
3. amino acids sequence is altered
4. uncontrollable cell division

Question 3

define epigenetics (2)

Answer 3

1. heritable changes in gene function
2. without changing the base sequence of DNA

Question 4

explain how increased methylation could lead to cancer (3)

Answer 4

1. methyl groups added to TSG
2. transcription of TSG is inhibited
3. leads to uncontrolled cell division

Question 5

give 1 way in which benign tumours differ from malignant tumours (1)

Answer 5

dont spread to other body parts

Question 6

explain how methylation of tumour suppressor gene can cause cancer (3)

Answer 6

• methylation prevents transcription of TSG
• protein that prevents cell division is not produced
• no control of mitosis

Question 7

explain why steroid hormones can rapidly enter a cell by passing through its cell surface membrane (2)

Answer 7

1. lipid soluble
2. diffuse through phospholipid bilayer

Question 8

1 MDs are a group of malignant cancers. In MDS,
the bone marrow doesnt produce healthy blood cells.
HSCT is one treatment for MDS. the patient receives stem cells from the bone marrow of a person who does not have MDS.
Before the treatment starts, the patient’s faulty bone marrow is destroyed.

(a) For some patients, HSCT is an effective treatment for MDS.
Explain how.

Answer 8

1. Produce healthy (blood) cells;
2. No MDS/faulty/cancerous (blood) cells;
3. Stem cells divide/replicate;

Question 9

MDS can develop from epigenetic changes to tumour suppressor genes.
In some patients, the drug AZA has reduced the effects of MDS. AZA is an inhibitor of DNA methyltransferases. These enzymes add methyl groups to cytosine bases.

Suggest and explain how AZA can reduce the effects of MDS in some patients (3)

Answer 9

1. (AZA) reduces methylation (of DNA/cytosine/gene);
2. (Tumour suppressor) gene is transcribed/expressed;
3. Prevents rapid/uncontrollable cell division

Question 10

3 SCD is a group of inherited disorders. People with SCD have sickle-shaped red blood cells.
A single base substitution mutation can
cause one type of SCD.
This mutation causes a change in the structure of the beta polypeptide chains in haemoglobin.
HSCT is a long-term treatment for SCD.
In HSCT, the patient receives stem cells from the bone marrow of a person without SCD. The donor is often the patient’s brother or sister. Before treatment starts, the patient’s faulty bone marrow cells have to be destroyed.

Use this information to explain how HSCT is an effective long-term treatment for SCD. (3)

Answer 10

1. Produce healthy (red blood) cells
2. No sickle/faulty/SCD (red blood) cells (produced)
3. Stem/marrow cells (continuously) divide/replicate
   OR
   Less chance of rejection (from brother/sister);

Question 11

6 Scientists have investigated the use of different types of stem cell to treat damage to the heart after a myocardial infarction. During a myocardial infarction, a number of different cell types in the heart die. This includes cardiomyocytes
which are heart-muscle cells.

Embryonic pluripotent stem cells (ESCs) can divide and differentiate into a wide
range of different cell types.

suggest one reason why ESCs might be
suitable to treat damage to the heart. (1)

Answer 11

(ESCs) can replace any type of (heart) cell;

Question 12

Embryonic pluripotent stem cells (ESCs) have not yet been used to treat people who have had a myocardial infarction. This is because of concern that the use of ESCs might lead to
more harm to the person.
One way that ESCs might lead to more harm is
by differentiating into the wrong types of cells.

Suggest one other way that putting ESCs into a person’s heart might lead to more harm to the person. (2)

Answer 12

1. Might divide out of control;
2. Leading to tumour / cancer;

Question 13

2 The binding of testosterone to an AR (androgen receptor) changes the shape of the AR. This AR molecule now enters the nucleus and stimulates gene expression.

Suggest how the AR could stimulate gene expression (2)

Answer 13

1. (AR is) a transcription factor;
2. Binds to DNA/promoter;
3. (Stimulates) RNA polymerase;

Question 14

in the cytoplasm, testosterone binds to a specific androgen receptor (AR).
An AR is a protein.
Suggest and explain why testosterone binds to a specific AR. (2)

Answer 14

1. Has a (specific) tertiary structure/shape;
   Accept in context of AR or testosterone.
   Ignore 3D.
2. (Structures are) complementary;