Genes

Question 1

In which stage of the cell cycle does the cell prepare for DNA Replication?

Answer 1

G1

Question 2

If the diploid chromosome number of a cell is 16, how many chromosomes and chromatids would the cell have at metaphase I of meiosis?

Answer 2

16 chromosomes, 32 chromatids

Question 3

Define synapsis, and at what stage(s) of cell division it occurs

Answer 3

Synapsis is the pairing up of two homologous chromosomes, and occurs in prophase I of meiosis

Question 4

What is the general phenotypic ratio in recessive epistasis?

Answer 4

9:4:3

Question 5

What is the general phenotypic ratio in dominant epistasis?

Answer 5

12:3:1

Question 6

What genetic principle is demonstrated by familial hypercholesterolaemia (mutation of the gene encoding LDL receptor), and how does this affect heterozygotes and homozygotes?

Answer 6

Incomplete dominance - heterozygotes have mild condition, homozygous recessives have severe condition

Question 7

What does the Y-axis on a Manhattan Plot represent?

Answer 7

The probability of association between individual SNPs and a disease

Question 8

Define the term ‘haplotype’

Answer 8

A set of SNPs which are close together in a small region of a chromosome

Question 9

Define the Barr Body

Answer 9

The inactivated X chromosome in the cells of female mammals

Question 10

Define linkage disequilibrium

Answer 10

Association of particular SNPs with each other in a given population

Question 11

Define the Pseudoautosomal region

Answer 11

A region of homologous DNA on the X and Y chromosomes of mammals (which allows them to pair during meiosis)

Question 12

Define Monosomy

Answer 12

When a cell or organism has one chromosome of a homologous pair missing

Question 13

When a male and female mouse, both heterozygous for a recessive, loss-of-function mutation in the maternally imprinted Igf2 gene, what is the expected phenotypic ratio of normal: dwarf offspring?

Answer 13

2 normal: 2 dwarf