Genetics

patterns in which single-gene traits and disorders occur in families.

Huntington disease is an example

Affects both sexes and appears in every generation

Cystic fibrosis is an example

Affects both sexes and can skip generationsthrough carriers

Follows one trait and the self-crossed plants are hybrids.P Parental generation | Tall × Short↓F1 All tall↓F2 1/4 Short: 3/4 Tall

each element (gene) separates in the gametes. This reflects the actions of chromosomes and the genes they carry during meiosis

carry same alleles TT or tt

carry different alleles Tt

Organism’s alleles

= Outward expression of an allele combination

Most common phenotype (Recessive or dominant)

Variant of a gene’s expression that arises when the gene undergoes mutation

Rules that explain the common patterns of single-gene transmission

Passing of a trait depends on whether:Gene is on an autosome (chromosomes 1-22) or on a sex chromosome (X and Y)Allele is recessive or dominant

A lethal genotype causes death before the individual can reproduce

Removes an expected progeny class following a specific cross. For example, a double dose of adominant allele may be lethal.

Heterozygous phenotype is intermediate between those of the two homozygotes

Heterozygous phenotype results from the expression of both alleles.

a cell surface glycoprotein and there are 3 alleles.

one allele produces A antigen. one allele produces B antigen. one allele does not produce antigens.