section 24.1 genes in populations

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Section 24.1LECTURE

SLIDES

Prepared by

Ashish MurthyRaritan Valley Community College

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SECTION 24.1 OUTLINE

Population Genetics

Gene Pools

Polymorphic/Monomorphic/SNP

Allele/Genotype Frequency*

Hardy Weinberg Principle*

Micro-Evolution*

POPULATION GENETICS

The Study of Genes and Genotypes in a population

Population - a group of individuals of the same species that occupy the same environment (that can interbreed)

Genetic Variation

Genetic Variation related to Phenotypic Variation

GENE POOLS

All of the alleles for every gene in a given population

Changes between Generations

Use to examine variation in alleles between individuals of a population

DIFFERENT TYPES OF GENES

Polymorphic – 2 or more alleles for a single gene that occur at greater than 1% frequency

Monomorphic – 1 allele for a single gene occurs at greater than 99% frequency

POLYMORPHISM Single Nucleotide Polymorphism (SNP)

Sickle Cell Anemia

Deletion

Duplication

ALLELE FREQUENCY

30 Homozygous Dominant Humans (TT) 20 Heterozygous Humans (Tt) 10 Homozygous Recessive Humans (tt)

Frequency of T: (30)(2) + 20 Frequency of t: (10)(2) + 20

(30+20+10)(2) (30+20+10)(2)

GENOTYPE FREQUENCY

30 Homozygous Dominant Humans (TT) 20 Heterozygous Humans (Tt) 10 Homozygous Recessive Humans (tt) Frequency of TT: 30 (30+20+10)

Frequency of Tt: 20 Frequency of tt: 10 (30+20+10)

(30+20+10)

HARDY-WEINBERG PRINCIPLE

Relates Allele Frequency and Genotype Frequency

Developed in 1908

Godfrey Harold Hardy and Wilhelm Weinberg

HARDY-WEINBERG VARIABLES

If p = 0.4, then q = 0.6

HARDY-WEINBERG EQUATION

EXAMPLE CALCULATION

HARDY-WEINBERG EQUILIBRIUM

P = .8 Q = .2

= = .64 = . 32 = .04

HARDY-WEINBERG ASSUMPTIONS

No new mutations

No natural selection

No random change in allele frequencies (large population)

No Migration

Random mating

MICRO-EVOLUTION

Changes in a population’s gene pool

Allele Frequency changes

New Genetic Variation

Evolutionary Mechanisms

SOURCES OF NEW GENETIC VARIATION

EVOLUTIONARY MECHANISMS