pop gen part 1
TRANSCRIPT
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