Genetics

Question 1

Chromosomal grouping:

Answer 1

1. Relative size
2. Position of centromere/kinetochore
3. Banding patterns

Question 2

Types of position of centromere:

Answer 2

• metacentric (p & q same length)
• submetacentric (slight difference in length of p & q arm)
• acrocentric (very short p arm compared to q arm)
• telocentric (centromere is at the end of chromosome)

Question 3

Chromosomes that are acrocentric:

Answer 3

Chromosome 3, 14, 15, 21, 22, Y

Question 4

What is point mutation?

Answer 4

Mutation in one base sequence

Question 5

Types of point mutation:

Answer 5

1. Silent mutation (mutated base seq still codes for the same a.a., hence no effect)
2. Missense (mutated base seq codes for a diff a.a.)
3. Nonsense (mutated base seq signals for STOP, hence no polypeptide chain and protein will form)
4. Frameshift (insertion/deletion/repetition that alters the whole reading frame, causing the a.a. seq after point of mutation to change)

Question 6

Types of inheritance:

Answer 6

1. Autosomal dominant (heterozygous)
2. Autosomal recessive (haemoglobinopathies, may skip a generation)
3. X-linked recessive/dominant
4. Co-dominant (ABO blood group: AB group)

Question 7

X-inactivation:

Answer 7

Also called lyonization. Females have two X chromosomes, hence one is silenced. Inactivation happens in somatic cells (descendants of that cell will have the same X chrom inactivated).