Vocabulary:
Allele -
One of a pair (or more) versions of a gene that occupies a specific position
(locus) on a specific chromosome.
Diploid -
Individual has two of each type of chromosome.
Homozygous -
Individual has two copies of the same allele.
Ex. AA or aa
Heterozygous -
Individual has one copy of two different alleles.
Ex. Aa
Genotype -
The specific alleles an individual has.
Ex. AA (dominant),
Aa (heterozygous), or aa (recessive)
Phenotype -
The observable characteristics of an individual, based on genetic and
environmental factors.
Ex. Brown hair, orange throat, AB blood type
Asexual:
Individual gets all genetic material from one parent. Progeny are genetically identical to
parent. Perfect replicator.
Sexual: Individual
gets genetic material from two parents.
For each gene, an individual receives one allele from each parent.
Haploid: inherit from both, but only across many
loci
Diploid: inherit from both for all loci
Autosomal
inheritance (Does not hold true
for sex chromosomes)
Hardy-Weinberg Law:
In
a population where individuals interbreed randomly, gene frequencies and
genotype ratios remain constant from generation to generation.
Assumptions:
Large
population
Population
is diploid
Individuals
interbreed randomly
|
|
P(Mating) |
P(AA) |
P(Aa) |
P(aa) |
|
AA x AA |
Dm
Df |
1 |
0 |
0 |
|
AA x Aa |
Dm
Hf |
0.5 |
0.5 |
0 |
|
AA x Aa |
Hm
Df |
0.5 |
0.5 |
0 |
|
AA x aa |
Dm
Rf |
0 |
1 |
0 |
|
AA x aa |
Rm
Df |
0 |
1 |
0 |
|
Aa x Aa |
Hm
Hf |
0.25 |
0.5 |
0.25 |
|
Aa x aa |
Hm
Rf |
0 |
0.5 |
0.5 |
|
Aa x aa |
Rm
Hf |
0 |
0.5 |
0.5 |
|
aa x aa |
Rm
Rf |
0 |
0 |
1 |
The probability
of producing a particular genotype is the summation of the probability of a
particular mating combination times the probability of that mating producing
the particular genotype.
See BarryÕs
Excel spreadsheet for details on calculating multi-generational probabilities.
DÕ = D2 +
½ (2DH) + ¼ H2
DÕ = (D +
½ H)2
DÕ = p2
HÕ = 2pq
RÕ = q2
QED