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ANTH222 Lecture Notes - Mendelian Inheritance, Point Mutation, Allele

1 pages103 viewsFall 2012

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Dr.Francis Allard

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Notes: 9/17 Variation/Evolution
Review of Last Class:
- Variation occurs as a result of mutation
- Point mutation- change in genes
- Meiosis/sexual reproduction- genes get reshuffled not created (crossing over,
independent assortment, etc.)
- Alleles- versions of a gene
- Recessive alleles only show when in homozygous conditions
- Environment only works on phenotype
- Evolution- change in allele frequency, happens at the population level (not individual)
Three Dimensions of Variation:
1. Now vs. Before (time period variation)
2. Here vs. There (location based variation)
3. Human vs. Animal (cross species comparisons)
Four Evolutionary Forced that Change Allele Ratio:
1. Mutation ultimate source of variations, but a weak evolutionary force, random and
2. Natural Selection amplifies mutations, major impact on ratio
3. Gene Flow outside genes coming into a population
4. Genetic Drift random change in allele frequency due to sampling variation in a finite
population, more amplified in smaller groups
a. Fonder Effect: a small portion of initial population begins a new population,
amplified by growth of population)
- 1-2% of DNA produces proteins/genes (RNA proteins etc.)
- 80% of “junk DNA” isn’t junk
Regulatory Sequences produce transcription factors that turn on/off genes that produce
Chimps and humans are 98.6% genetically similar. The difference between chimps and
humans is form regulatory sequences and when they turn on/off protein genes.
Ex. chicken vs. snake (necks)- same genes, just different regulators (one’s on,
one’s off)
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