hardy Weinberg equilibrium.pptx.com..pk.
- 1. Hardy Weinberg equilibrium Submitted to: Dr. Khalid Mukhtar Submitted by: Amna Akram Roll no.: ZOOL51F22R002 BS ZOOLOGY
- 2. Hardy Weinberg equilibrium Submitted to: Dr. Khalid Mukhtar Submitted by: Amna Akram Roll no.: ZOOL51F22R002 BS Zoology 5th regular University of Sargodha
- 3. Introduction • In population genetics, the Hardy–Weinberg principle, also known as the Hardy–Weinberg equilibrium, model, theorem, or law, states that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences.
- 4. History • Independent Discovery (1908): • ○ Godfrey Harold Hardy: A British mathematician who formulated the principle in a letter to the Science magazine. ○ Wilhelm Weinberg: A German physician who independently derived the same principle. • Significance: ○Provided a mathematical framework to understand genetic stability in populations. ○ Challenged the prevailing notion that dominant alleles would automatically increase in frequency.
- 6. Basic concepts: • Genome- Complete set of DNA, including all of it’s genes(of organism). In human being, copy of entire genome more than 3billion DNA base pairs in all cells that have nucleus. • Gene frequency- Relative proportion of a particular genes or alleles of single locus in a population. When we consider a particular gene on single locus in population, then we note the probability of a particular genes. One character dominant in a population while other is recessive.
- 7. Cont… • Genotypic Frequency-Relative proportion of a particular genotype in population. • Population Genetics-Study of allele frequency and genotype frequency. • Population-It is freely interbreeding group of individuals. • Allele frequency- It is number of individuals alleles of certain type divided by total number of alleles of all types in a population. • Gene locus- It is the portion on chromosome that representing single gene.
- 8. Hardy Weinberg equation • For example – • If the frequency of allele ‘A’ in the population is ‘p’ and the frequency of allele “a” in the population is “q”. Then the frequency of genotype AA=p² the frequency of genotype Aa=2pq the frequency of genotype aa= q² mathematical, p+q=1 • p² + 2pq + q2 = 1
- 10. Hardy Weinberg Assumptions 1. Random mating 2. Very large population 3. Absence of natural selection 4. No gene flow or migration 5. No mutation 6. Genetic drift
- 11. Random mating • Organisms mate randomly with each other, no preference with a particular genotypes. This type of mating leads to the resultant production of the same number of offspring for all females in a population which tends to maintain genetic equilibrium. Hence, to attain the genetic equilibrium, random mating should occurring in the population.
- 12. Rando m mating
- 13. INFINITE LARGE POPULATION • To maintain the genetic equilibrium the population should be effectively infinitely large in size. Because of that genetic drift is not causing a random changes in allele frequencies due to sampling error from one generation to the next generation.
- 14. Natural Selection Is the differential survival and reproduction of individuals due to difference in the phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristics of the population over the generation. Hence, to apply the Hardy-Weinberg law the natural selection should be absent.
- 16. • Migration is the movement of an organisms from one place to another with intent to settle. Causes of migration due to environmental condition / factors need for resources due to over population were often cause migration. M Migration/ Gene flow
- 17. NO GENE FLOW / MIGRATION Immigration Coming into groups/population from other area. Emigration Emigration Leaving habitat area to move to another area.
- 18. CONTS. • Migration is ultimately leads to genes disturbs in the population. • It is responsible for adding and deleting the alleles from the population. Due to gene flow, population becomes unstable and disturbs the genetic equilibrium. Hence, migration should not be present in the population to attains the Hardy-Weinberg equilibrium.
- 19. Mutation • Mutation is the alteration in the nucleotide sequence in the genome of an organism, virus or extra-chromosomal DNA. Mutation is the ultimate source of genetic variation, preventing populations becoming genetically homogeneous situations where they otherwise would.
- 20. Genetic drift • Genetic drift :- Genetic drift is a change in the frequency of an allele within a population over time. This change in frequency of the allele or gene variation must occur randomly in order for genetic drift to occur
- 21. Use of hardy Weinberg equilibrium • 1. Identify the known genotype frequencies. • 2. Calculate the allele frequencies (p and q). • 3. Use the allele frequencies to calculate the expected genotype frequencies. • 4. Compare the expected and observed genotype frequencies.
- 22. Example: A Population of Flowers • Scenario: In a population of 100 flowers, 36 are red (dominant phenotype), and 64 are white(recessive phenotype). Steps:1. Calculate q² (frequency of white flowers): q² = 64/100 = 0.64 • 2. Calculate q (frequency of the recessive allele): q = √0.64 = 0.83. Calculate p (frequency of the dominant allele): p = 1 – q = 0.2 • 4. Calculate the expected genotype frequencies: p² = 0.04 (homozygous dominant) 2pq = 0.32 (heterozygous) q² = 0.64 (homozygous recessive)
- 23. Real-world Examples of Hardy-Weinberg Equilibrium and Deviations • Human populations: Examples of genetic disorders like cystic fibrosis and sickle cell anemia. Animal populations: Studies on populations of birds, insects, and mammals. • Plant populations: Investigations of flower color, seed shape, and other traits.
- 24. Conclusions • Hardy-Weinberg equilibrium is a powerful tool for understanding population genetics. By understanding the assumptions and limitations of this model, we can gain insights into the forces shaping the genetic makeup of populations over time.