Complex Inheritance of Human Traits
Codominance With codominance, a cross between organisms with two different phenotypes produces offspring with a third phenotype in which both of the parental traits appear together..
Codominance Examples
Multiple Alleles Control: 1. blood type: I A, I B, i I A and I B are codominant Table on page 331 It is important that one know his/her blood type Blood transfers Parentage
Polygenic Inheritance Inheritance controlled by two or more genes (Aa x Bb x Cc) found on same or different chromosomes Ex. Stem length in plants, skin color
Controlled by 3-4 pairs of genes Genes are controlled by the production of melanin (a chemical that adds brown color to the skin; the darker a person is the more melanin one has) Skin Color
Non-Disjunction Failure of the chromosomes to separate during meiosis. This may result in offspring either having too many chromosomes or not enough
Down’s Syndrome Extra 21 st chromosome Trisomy 21 Karyotype
Monosomy X Female missing a chromosome X Turner’s syndrome
Klinefelter’s Syndrome Male with extra chromosome (XXY)
Genetic Disorders Causes errors in the genetic material Sickle Cell Anemia – red blood cells have a sickle shape instead of an oval. Found in African Americans Mostly or dark – skinned people. Cells clog blood vessels causing pain and early death
Normal Blood CellSickle Cell
Environment can play a major role in genetics 1. Internal factors – Hormones Horn Size 2. External factors—Arctic Fox Temperature Nutrition Light Chemicals Infectious agents