multiple alleles – blood type

d. Multiple Alleles – Instead of having two forms of an allele, there are more than two for one gene.

i. The best example for humans is blood. There 3 alleles for blood types in humans: A, B and O. A and B are co dominant while O is recessive.

Multiple Alleles – Blood Type

Type A genotypes could be: IAIA or IAi.

Type B genotypes could be: IBIB or IBi.

Type AB genotype is: IAIB

Type O genotype is: ii

Practice

A man who is heterozygous for type A blood marries a woman who is heterozygous for type B blood. Find the possible outcomes

e. Sex linked traits

i. Autonomies – there are 44 (22, pairs) of non sex chromosomes.

ii. Sex Chromosomes – the 23rd pair of chromosomes are the sex chromosomes.

The genotype for females is XX; the genotype for males is XY.

e. Sex linked traits

iii. Sex linked traits – Are genes located on the X chromosome. There is almost no information located on the Y chromosome.

Since males have only one X chromosome they show whatever allele is on the X chromosome, regardless of whether it is dominant or recessive.

e. Sex linked traits

iii. This is the only time that a single recessive allele is expressed.

Two examples of sex-linked traits in humans are red/green colorblindness and hemophillia. (A recessive sex linked trait that keeps your blood from clotting.)

Color Test

Color Test

Color Test

Color Test

Sex linked traits - Colorblindness1. If normal vision (N) is

dominant to colorblindness (n) give the genotypes for each of the following:

A female carrier: XNXn

A homozygous dominant female: XNXN

Colorblind male: XnYColorblind female: XnXn

A male with normal vision: XNY

Sex linked traits• Who does the male get

the X chromosome from? Mother

• Who does a male inherit recessive sex linked traits from? Mother

• Who are colorblind more often, men or women? Men; no information on Y to mask the recessive trait on X.

Practice

A female carrier has a child with a male with normal vision. What are the chances of colorblindness occuring in:

Son?

Daughter?

Practice

A colorblind male has a child with a normal female. Fill out the cross.