Chapter 7 Extending Mendelian Genetics

Karyotype = picture of all chromos in cell They can show a change in chromos whether autosomal or sex-linked

Autosomal recessive disorders  take 2 copies of the recessive Ex. Albinism Ex. Cystic fibrosis Ex. Tay-Sachs disease A carrier has 1 recessive, doesn’t show symptoms

Autosomal dominant disorders  less common, only take 1 dominant Ex. Achondroplasia (dwarfism) Ex. Huntington’s disease

Sex linked genes (those on X & Y) also affect inheritance Since males have 1 X (XY) they show all alleles on X (even recessive) Ex. Color blindness is more common in men  3 genes on X chromo

Females are carries for sex-linked disorders Ex. Queen Victoria carried the allele for hemophilia (on X)  passed on to many in royal family

Not all alleles follow the dominant vs. recessive pattern Ex. Red flowers x white flowers = pink flowers Incomplete dominance = neither allele is completely dominant Heterozygous shows a blend of the traits

Codominance = both alleles are expressed Ex. Speckled chicken Heterozygous shows both traits

Human example of codominance = blood type Controlled by 3 allels; I A, I B, i I A and I B are codominant, i is recessive Also an example of multiple alleles

Polygenic trait = trait controlled by 2 or more genes Ex. Skin color in humans is controlled by 4 genes Ex. Human eye color is controlled by at least 3 genes

Phenotypes can also be affected by the environment (nutrition, exercise, health care)

A pedigree chart = genetic family tree (shows genos and phenos) Squares = males; circles = females Shaded in = has trait; not shaded = no trait

Pedigrees can be used to determine genotype based on whether the trait is autosomal or sex- linked, dominant vs. recessive