7A Linkage and Epistasis

Question 1

How are chromosomes sex linked

Answer 1

The genetic information for biological sex is carried on 2 sex chromosomes
Females XX
Males XY
An allele is sex linked when the allele that codes for it is located on a sex chromosome

Question 2

Compare the X chromosome to the Y chromosome

Answer 2

Y is smaller and carries fewer genes

Question 3

Why are males more likely to display recessive phenotypes for genes that are sex linked

Answer 3

The only have one X chromosome so they only have one allele for sex linked genes

Question 4

Examples of genetic disorders caused by faulty genes ( x linked disorders)

Answer 4

Colour blindness and haemophilia

Question 5

Define autosome

Answer 5

Any chromosome that isn’t a sex chromosome
Autosomal genes are located on the autosomes

Question 6

Why are genes on the same autosome said to be linked

Answer 6

They stay on the together during independent segregation of chromosomes in meiosis I and their alleles will be passed on to offspring together unless crossing over splits them up first
The closer together two genes are on the same autosome the more closely they are said to be linked as crossing over is less likely to split them up

Question 7

Function of an epistatic gene

Answer 7

To mask the expression of another gene

Question 8

How to many different genes control the same characteristic

Answer 8

They interact with each other