Variation Within Species & Mutations and Selective Advantage

Patrick Zisser and Peter Dyloco

A group of organisms that can interbreed in nature and produce fertile offspring

Species

A part of a chromosome that governs the expression of a trait and is passed on to the offspring; it has a specific

DNA sequence

Gene

WHAT IS GENETIC VARIATION?

Genetic Variation

The different allele combinations in a species that cause differently expressed

phenotypes and genotypes

Cause of Genetic Variation

Order of bases in nucleotides

Variation Within Species

Sexual Reproduction

Inheritance of different alleles

Genetic Variation• Reflected in phenotype• Reflected in unseen genetic

makeup

Selective Advantage

Survival

Factors in Genetic Variation

1. Total variety of genetic informationA. Independent AssortmentB. Crossing over/random segregation

2. Mutations3. Gene flow

Genetic Diversity: Total Variety of Genetic Information

VS.

A permanent change in the genetic material of an organism, the only source of new genetic variation

Mutation

CAUSES OF MUTATION

Causes of Mutation

• Natural:– Errors during DNA replication or meiosis

• Environmental– Mutagens• Radiation• Viruses• Transposons• Chemicals

Natural: occurs during DNA replication or meiosis; when DNA is copied and before cell divides (S phase)

175 mutations vs. parent

Environmental: Mutagens - Radiation

Environmental: Mutagens - Viruses

Environmental: Mutagens - Transposons

A segment of DNA that can become integrated at many different sites along a chromosome (especially a segment of bacterial DNA that can be translocated as a whole)

Environmental: Mutagens - Chemicals

Gene Flow

The net movement of alleles from one population to another due to the migration of animals

RESULTS OF MUTATION

1.Cell death2.Cell malfunction3.Selective advantage

Cell Death and Malfunction

Mutation

Product of gene changed and/or cell malfunctions• 70 percent are harmful

Cell death caused by malfunction

Mutations in somatic cell disappear after death of organism Only mutation in gamete cell may pass trait as new allele

Note

A genetic advantage that improves an organism's chance of survival usually in a changing environment

Selective Advantage

Example I: Daphnia

Example II: Bacteria

P1 generation

F1 generation mutation I

Survives antibiotic

F2 generation mutation I

Dies

F2 generation mutation II

Dies

F2 generation mutation III

Survives antibiotic

F1 generation mutation II

Dies

F1 generation mutation III

Dies

End.