Chapter 3Chapter 3

Population GeneticPopulation Genetic

Concept review…Population genetic

Gene pool concept

Hardy-Weinberg

Law

At the end of the lesson, you should be able to :

a)Gene pool concept:- Explain gene pool and allele frequency- Explain population genetics and its relation

to allele frequency- Explain allele frequency and genetic

equilibrium

Gene pool conceptGene pool concept

Gene pool conceptGene pool concept• Studies the change of frequencies of alleles within a

population

• Population :- a group of individuals of the same species that live in a habitat & may interbreed to produce fertile

offspring

- shares a same gene pool

• Gene pool - total aggregate of genes in a population at any one time

- consists of all alleles at all gene loci in all individuals of the population at a given time

Gene pool conceptGene pool concept

• For a diploid species, each locus is represented twice in the genome (homozygous / heterozygous)

• Eg: - A study was done on 10,000 rats, focusing on the fur colour (determined by dominant allele A & recessive allele a)

- Data: AA individuals = 6,000 Aa individuals = 2,000

aa individuals = 2,000

:. Total number of alleles for fur colour = 2(6000) + 2(2000) + 2(2000) = 20000

Gene pool conceptGene pool concept• Each of the allele types has a relative frequency in the gene pool

• Allele frequency: ratio of any given allele in a population, relative to all the other alleles of that gene at the same locus

• Eg: - Using the previous data, calculate the allele frequencies for A & a in the gene pool - Total of A alleles = 2(6000) + 1(2000)

= 14000

- Total of a alleles = 2(2000) + 1(2000)= 6000

- Frequency for A alleles = 14000 / 20000 = 0.7

- Frequency for a alleles = 6000 / 20000 = 0.3

Gene pool conceptGene pool concept

• For a gene locus where only 2 alleles occur in a population, allele frequencies can be calculated using this equation :

p + q = 1

p = frequency of the dominant allele q = frequency of the recessive allele

• If q = 0.3, p = 1 – 0.3= 0.7

Gene pool conceptGene pool concept

• Allele frequencies in a gene pool determine the genetic change for a population

• Naturally, the composition of a gene pool may change over time due to certain factors

• Change in allele frequencies

Change in gene pool

Change in genetic composition of population

Evolution

Gene pool conceptGene pool concept

• If no change in allele frequencies from one generation to the next, the gene pool is considered static

• This shows that the gene pool is in genetic equilibrium

Sekilas pandang…

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Sekilas pandang…

Thank you for your attention