FUNBIO 21 - Transmission genetics: Chromosome mapping, multiple alleles

Question 1

Define Multiple Alleles

Answer 1

When there or more alternative kinds of genes occupy the same locus.

Question 2

Explain the ABO system.

Answer 2

There are four blood groups: A, B, AB, and O. This is due to RBCs having different agglutinogens (antigens) on their surface that are recognized by specific agglutinins (antibodies) in the serum of an opposite type.
Antigen A: likes Antibody B, can receive type A or O
Antigen B: likes Antibody A, can receive type B or O
Antigen AB: likes none, universal receiver
O: likes Antibody A & B, universal donor

Question 3

Define Polygenic Inheritance.

Answer 3

Traits not controlled by a single allele.
Ex: height
Ex: skin pigmentation (the more dominant alleles, the darker the skin)

Question 4

What is the pseudoautosomal region?

Answer 4

Small regions at the tips of the Y chromosome that correspond with a small region on the X chromosome, allowing for recombination between them.

Question 5

What happens in the absence or presence of the Y chromosome.

Answer 5

The sex-determining region or testis-determining region or SRY is near the pseudoautosomal region and indicates the development of male body parts. Absence of the Y chromosome leads to the development of female body parts. Often, the SRY can be relocated to an X chromosome by recombination, leading to an individual that is phenotypically male, but genotypically female.

Question 6

Compare X-linked and Y-linked genes.

Answer 6

X-linked genes are recessive for females, but dominant for males. Y-linked genes are dominant and passed down to all sons. Example: Haemophilia A is a recessive X-linked mutation, which produces an inactive clotting factor for the intrinsic pathway for blood clotting.