* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download DNA & RNA
Quantitative trait locus wikipedia , lookup
Point mutation wikipedia , lookup
Behavioural genetics wikipedia , lookup
History of genetic engineering wikipedia , lookup
Site-specific recombinase technology wikipedia , lookup
Gene expression programming wikipedia , lookup
Inbreeding avoidance wikipedia , lookup
Public health genomics wikipedia , lookup
Genetic engineering wikipedia , lookup
Genetics and archaeogenetics of South Asia wikipedia , lookup
Medical genetics wikipedia , lookup
Pharmacogenomics wikipedia , lookup
Designer baby wikipedia , lookup
Genome (book) wikipedia , lookup
Koinophilia wikipedia , lookup
Human leukocyte antigen wikipedia , lookup
Polymorphism (biology) wikipedia , lookup
Human genetic variation wikipedia , lookup
Dominance (genetics) wikipedia , lookup
Population genetics wikipedia , lookup
Hardy–Weinberg principle wikipedia , lookup
Changing Allele Frequency Chapter 23 What you need to know! • The conditions for Hardy-Weinberg Equilibrium • How to use the Hardy-Weinberg equation to calculate allelic frequencies and to test whether a population is evolving Sources of Microevolution • Changes in the allele frequency of a single population • Only populations can evolve (not individuals) • Natural Selection: differential reproductive success of certain phenotypes lead to a(n) increase/decrease of certain alleles • Mutation: introduces new alleles • Gene flow: add or remove alleles to a gene pool based on migration Sources of Microevolution • Genetic Drift: Random change of allele frequency in small populations • Founder Effect: spike in gene change due to genetic drift after a small population inhabits a new region • Bottleneck effect: a small surviving group (near extinction) gives rise to a new population with a dramatically different gene pool Sources of Microevolution • Non-random mating: • Sexual Selection • Mating more often occurs between close neighbors than distant neighbors • Inbreeding in small populations Genetic Equilibrium • In 1908, 2 mathematicians (Hardy & Weinberg) stated that the allelic frequency in a given population accounts for changes in populations • They develop the concept of genetic equilibrium: how alleles in a population could stay constant from one generation to another (no evolution) Equilibrium Requires 1. 2. 3. 4. 5. No natural selection No mutations No gene flow No genetic drift Random mating Variables • We have two copies (alleles) for each gene – Dominant alleles – Recessive alleles • p = frequency of dominant alleles – p = (# of dominant alleles)/(total alleles) • q = frequency of recessive alleles – q =(# of recessive alleles)/(total alleles) • Check your work: p + q = 1 Example • A rabbit population has two different alleles for fur color: • B = brown and b = white • The rabbit population has 50 members • 25 rabbits are BB - brown • 10 rabbits are Bb - brown • 15 rabbits are bb – white • Find p and q Genotypic Frequency in Equilibrium • • • • • Homozygous dominant genotypes = p2 Heterozygous genotypes = 2pq Homozygous recessive genotypes = q2 The sum of all genotypes = 1 p2 + 2pq + q2 = 1 Example • Are our rabbits in genetic equilibrium? • p = .6, and q = .4 Equilibrium Actual p2 = 25/50 2pq = 10/50 q2 = 15/50 • Since the numbers are not identical, we know this population is not in HardyWeinberg equilibrium