Patterns Of Heredity & Human Genetics

Patterns of Heredity & Human Chapter 12 Genetics

Pedigrees illustrate inheritance Pedigree: a graphic representation of genetic inheritance.

Simple Mendelian Inheritance Attached earlobes (ff) Widow’s peak (Ww or WW) Hitchhiker’s thumb (Hh or HH) Cleft chin (Cc or CC)

Incomplete dominance Incomplete dominance: the phenotype of

heterozygous individuals is intermediate between the 2 homozygotes.

Codominance: Expression of both alleles Codominant alleles:

cause both phenotypes to be produced BB = black chickens WW = white chickens

Codominance in Humans Sickle cell anemia

Multiple Alleles The gene that controls feather color in pigeons

has multiple alleles (each individual can only have 2 alleles of a gene)

Blood type in humans is an example of codominant inheritance The alleles for blood type are A, B, O (P325)

Multiple Alleles

Sex determination Autosomes: chromosomes 1-22 Sex chromosomes: Chromosome 23 Females (XX) Males (XY)

Sex-linked Inheritance Sex-linked traits are traits controlled by genes

located on sex chromosomes

X-linked disorder

Sex-linked traits in humans Red green color blindness Hemophilia

Polygenic Inheritance Polygenic inheritance: traits that are controlled

by two or more genes

Polygenic traits in humans

Abnormal # of chromosomes

Environmental influences on gene expression