Sex Chromosomes and Linkage

These flashcards cover key concepts related to sex chromosomes, genetic linkage, and examples of inheritance patterns such as haemophilia and colour blindness.

What are the two sex chromosomes in mammals?

X and Y chromosomes.

What is the usual sex chromosome combination for males and females?

Males: XY, Females: XX.

What does a Punnett square show regarding offspring probability?

The probability of having male or female offspring is 50%.

What are sex-linked characteristics?

Characteristics coded for by genes found only on sex chromosomes.

Which chromosome carries fewer genes, X or Y?

Y chromosome.

What is an example of a condition that is X-linked?

Colour blindness and haemophilia.

What does it mean for a male to have one allele of an X-linked gene?

Males express the characteristic of this allele even if it is recessive.

Can males be carriers of X-linked genes?

No, males cannot be carriers of X-linked genes.

What happens when a carrier female and affected male have children in terms of colour blindness probability?

There is a 50% chance of producing a child with colour blindness.

What is autosomal linkage?

Genes on autosomes that can be inherited together.

How does the proximity of genes on a chromosome affect inheritance?

Genes found close together are more likely to be inherited together.

What evidence is there for crossing over during meiosis?

The presence of recombinant gametes with linked genes.

What ratio is expected from unlinked genes during dihybrid crosses?

9:3:3:1.

How does crossing over affect alleles on the same chromosome?

It can put new alleles together in combination.