Patterns of Heredity & Human Genetics Chapter 12 Patterns of Heredity & Human Genetics

Pedigrees

Simple Recessive Heredity Most disorders are caused by recessive alleles Cystic fibrosis Tay-sachs disease Phenylketonuria

Simple Dominant Heredity Only one dominant gene causes the trait to appear Huntington’s disease

Incomplete Dominance Heterozygous individual shows a third trait A blending of the dominant and recessive

Codominance Heterozygous individual shows both traits at the same time Blood type, sickle cell anemia

Sex Determination Humans have 46 chromosomes 22 pairs of autosomes 1 pair of sex chromosomes XX is female XY is male

Sex-linked Disorders Usually more common in males than females Colorblindness Hemophilia

Sickle Cell Anemia Created through mutation of a single base pair Disease of the red blood cells Found mainly in people of African ancestry

Multiple Alleles Characteristic controlled by more than two alleles Results in more than two possible outcomes Skin color, eye color, height

Karyotype

Down Syndrome

Turner Syndrome

Klinefelter Syndrome

Blood Types Controlled by three genes: IA, IB, i Two genes are codominant One gene is recessive Results in 4 blood types: A, B, AB,O