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# Pop gen part 1

## on Jan 25, 2011

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## Pop gen part 1Presentation Transcript

•
• Chapter 3 Population 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 concept
• Gene 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 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 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 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 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 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… “ Hiduplah dengan penuh cita-cita & harapan, jadilah manusia yang sentiasa berpandangan jauh dan berwawasan…”
• Sekilas pandang… Thank you for your attention