Genetics, Populations, Evolution and Ecosystems: Inheritance - Linkage

Question 1

What are the two ways in which genes can be linked?

Answer 1

• Sex-linked genes
• Autosomal genes

Question 2

What is sex-linkage?

Answer 2

• Some characteristics are sex-linked
• When genes are located on the X or Y chromosomes

Question 3

Why are most genes on sex chromosomes called X-linked genes?

Answer 3

• Y chromosome is smaller than X chromosome so carries fewer genes
• Most genes on sex chromosomes are only carried on X chromosome (called X-linked genes)

Question 4

Why are males more likely to express recessive phenotypes for sex-linked genes?

Answer 4

• Males only have 1 X chromosome so often only have 1 allele for sex-linked genes
• Only 1 recessive allele needed for its characteristic to be expressed

Question 5

What are autosomes and autosomal genes?

Answer 5

• Autosomes are any chromosomes that aren’t a sex chromosome
• Autosomal genes are genes located on autosomes

Question 6

What is autosomal linkage?

Answer 6

• Genes on the same autosome
• Linked because they stay together during independent segregation of chromosomes in meiosis I
• Unless if separated during crossing over