Human Genetics

Sex Chromosomes XX = girl XY= boy

Sex-linked Traits traits on the sex chromosomes X chromosome has about: 1000 genes Y has about: 26 genes

Sex-Linked Traits Most debilitating (harmful) sex-linked traits are recessive Females must get 2 alleles on both X chromosomes to get these diseases If males get 1 allele on their X chromosome then they get the disease

Examples of Sex-Linked Genetic Diseases Hemophilia :1 or more blood clotting factors not produced People can’t stop bleeding

Muscular Dystrophy a muscle disorder that results in weakening and loss of skeletal muscles

Male Pattern Baldness

Red-Green Color Blindness Individual can’t see red and green colors Found in 1 in 10 males and 1 in 100 females in the U.S.

Tests for Red-Green Colorblindness

What numbers are in the circles?

Example Problem Cross a normal female with a color blind male How many of their daughters will be color blind? What about their sons?

Cross a color-blind male with a carrier female. Will any of their sons be color-blind? Any of their daughters?

Cross a normal male with a carrier female Cross a normal male with a carrier female. What kind of children will they have?