BIOL 1010 Lecture Notes - Lecture 5: Allele Frequency, Gene Pool, Sexual Reproduction
11 Oct 2018
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Genetic Variation 3
Genes are located at specific places on the DNA strand called loci.
All individuals of the same species possess the same genome-the complete set of genetic information
and associated DNA. NO two individuals have the same genotype. Natural selection acts on the
phenotype of individuals, the amount of DNA found in different species varies. Some species are
polyploidy, they have three or more complete sets of chromosomes. Large genomes have a greater
potential for genetic diversity and a greater number of targets for mutation. The greater the number of
genes, the greater the extent of genetic variation there will be within a species and from individual to
individual, because there exists a greater number of potential different combinations of alleles. Sexual
reproduction increases the genetic diversity among members of the same species that live in a particular
area.
Gene pool: total of alleles within a population
Allele frequency: proportion of gene copies in a population of a given allele
Evolutionary changes in a population can be measured in part by looking for changes in allele
frequencies.
If there were only one allele for a particular gene, that allele’s frequency would be 100 % and it would
be considered fixed.
Hardy –Weinberg Principle
The allele frequencies will not change from generation to generation, provided that
The population is very large, mating opportunities are equal, no mutation occurs, no migration occurs,
no natural selection occurs- all individuals have an equal chance of reproductive success.
P + q = 1
P2 +2pq +q2 = 1 p=frequency of allele A, q= frequency of allele a, p2= frequency of AA genotype,
2pq= frequency of Aa genotype, q2= frequency of aa genotype
Key factors that can cause evolution:
When a population is small, the chances can cause changes in allele frequencies, individuals (mates) that
are preferred will pass on their alleles, genetic mutations occur, new alleles may be created, or an allele
may be changes into another, changing the frequencies of both new and original alleles, migrating, they
remove alleles from one population and add to another, natural selection, when certain alleles, thus
traits have greater reproductive success that others, their relative frequency of these `favoured` alleles
increases in the next generation.
4 different ways: Genetic Drift, gene flow, mutations, natural selection
Document Summary
Genes are located at specific places on the dna strand called loci. All individuals of the same species possess the same genome-the complete set of genetic information and associated dna. Natural selection acts on the phenotype of individuals, the amount of dna found in different species varies. Some species are polyploidy, they have three or more complete sets of chromosomes. Large genomes have a greater potential for genetic diversity and a greater number of targets for mutation. The greater the number of genes, the greater the extent of genetic variation there will be within a species and from individual to individual, because there exists a greater number of potential different combinations of alleles. Sexual reproduction increases the genetic diversity among members of the same species that live in a particular area. Gene pool: total of alleles within a population. Allele frequency: proportion of gene copies in a population of a given allele.
