Discuss the ways the genome and the environment interact to produce a phenotype

Question 1

1. Give 4 examples of diseases which have strong genetic influence
2. Give 4 examples of diseases which have strong environmental influence

Answer 1

• Genetic:

1. Duchenne muscular dystrophy
2. Phenylketuonuria (PKU)
3. Galactosemia
4. Heamophilia

• Environmental

1. Scurvey
2. TB
3. CVD
4. Diabetes

Question 2

Define monogenic and multifactorial disorders and give 4 features of each

Answer 2

• Monogenic: Defects in one gene

1. Rare
2. Genetic simple
3. Unifactorial
4. High recurrence rate within families

• Multifactorial: Environment + genetics

1. Common
2. Genetic complex
3. Multifactorial
4. Low recurrence rate within families

Question 3

Give 2 features and 3 examples of polygenic inheritance:

Answer 3

• Phenotype determined by many genes (at different loci)
• Traits = continious distrubution
• Blood pressure, height, weight

Question 4

Define heritability and give 4 ways to gain evidence about heritability

Answer 4

• Proportion of variance in aetiology

1. Familial risks
2. Twin studies
3. Adotion studies
4. Population and migration studies

Question 5

Define the term epigenetics?

Answer 5

• The study of how the expression of DNA can be changed without changing the sequence of DNA

Question 6

DNA methylation: Define, methylation enzyme, donor, consequence

Answer 6

1. Methyl group is added to a CpG site
2. DNA methyltransferase (DNMT3a & DNMT3b)
3. S-adenosyl methotinine (SAM)
4. Gene silencing (of promoter regeions)

Question 7

What are histones?

Answer 7

• Proteins which condense and structure DNA into nucleosomes

Question 8

Histonne methylation: Define, enzymes, consequence

Answer 8

• Methyl groups added to lysine (K) and arginine (R)
• Histone methyltransferase (HMTs)
• Activate/repress transcription

Question 9

Histone Acteylation: Define, enzyme, donor, consequence

Answer 9

• Acetyl groups added to lysine residues on the histone N-terminal tail
• Histone acetyltransferase (HATs)
• Acteyl CoA
• Activate transcription of gene

Question 10

Why does acteylation lead to transcription of a gene?

Answer 10

• By adding the acetyl group to the lysine, it will neutralise its positive charge which would therefore weaken the attraction between the DNA molecule and histone tail.

Question 11

What are mutagens and consequences and give 4 examples?

Answer 11

• External agent that increases the risk of mutation
• Irreversible and hertiable changes to DNA
• Carcinogens, x-rays, ultra-violet radiation, radioactive substances