Anthro 105: 01/23/11 – Class Notes

Read chapter 12 for Weds.

 

X-Linked Hemophilia

  • Gene is located on the X-chromosome, thus males and females are affected differently.
  • Females = XX
  • Males = XY
  • Hemophiliac Male (XhY) – only 1 X-Chromesome with recessive gene causes disorder.
  • Hemophiliac Female (XhXh) – both X’s must carry the recessive gene.
  • A male hemophiliac cannot pass the gene to his son, only his daughter as he only passes on the Y to his sons.

Polygenetic Inheritance

  • Two or more genes contribute to the phenotypic expression of a single characteristic
  • These traits show gradations, there is a series of measurable intermediate forms between two extremes.
  • Hair, eye and skin color are polygenetic traits.
  • Traits can be influenced by your environment.
  • Regulatory genes: can mask expression of some traits.
  • Skin color is governed by at least 12 alleles.

Discontinuous Distribution of Mendelian Traits

  • Shows discontinuous distribution of ABO blob type in a hypothetical population
  • Described in terms of frequency.
  • Continuous Expression of a Polygenetic Trait
    • Represents the continuous expression of height in a large group of people.

Population Genetics

  • Evolutionary forces bring about change in the gene pool of a population.
  • Four evolutionary forces are recognized by scientists (mutation, natural selection, gene flow, genetic drift).

Evolutionary Forces

  1. Mutation: a change in the DNA.
    1. The source of genetic variation.
    2. In humans, occurs at a rate of ~30 mutations per million sex cells formed.
  2. Natural Selection: factors in the environment exert pressure favoring some individuals over others.
    1. Acts on variation
  3. Gene Flow: The exchange of genes between populations.
  4. Genetic Drift: random changes in gene frequency from one generation to the next.
    1. Related to smaller population size.
    2. founder effect.

* Additional factors: female choice, unequal fertility, consanguineous mating, isolating mechanisms.

To read these notes in their original format (from the Evernote for Mac application) on the Evernote website click here.

Posted by on Jan 25, 2012 in Anthropology, Class Notes, WCC | 0 comments