GENOTYPE, PHENOTYPE, AND VARATION

LECTURE 6

Phenotype

Physical appearance or attributes of an organism

Genotype

Genetic make-up of an individual

Dominance vs. Recessive vs. Incomplete Dominance

• One allele determines the phenotype of a diploid genotype

• One allele expression is ‘masked’ by dominant allele

• Refers to intermediate representing of both homozygous traits

Environmental Variation

• organisms differing in characteristics due to differences in environmental factors

  • phenotypic plasticy: Ability to change phenotype due to environmental factors ( organisms that have same genetic make-up look/behave differently )

  • canalized genotypes are restraint to environmental variation

Genetic Varation

Changed in genetic make-up of a species ( aka SNPs )

Mutations

• Somatic Mutations: mutations that aren’t inherited to next generation

• Germ-line Mutations: mutations that are inherited to next generation

  • Germ-line mutations are important for evolution to take place

Haplotypes

SNPs that are typically inherited to one another ( relative close to one another on chromosome )

Nucleotide Diversity

Measure of genetic variation within a population by taking average number of nucleotide differences per site between 2 DNA sequences

Point Mutations

• Single nucleotide change

  • Synmonyms

  • Non-synmonyms

  • Transition: purine/pyrimind replace with other of their own

  • Tranversion:purine/pyrimind replaced with other

Bigger Mutations

• Deletions: section of DNA is removed

• Duplication: section of DNA is repeated

• Fission/Fusion: chromosome broken into two; 2 chromosome come together as one

• Translocation: piece of chromosome moves to another

• Transposable: genes moves to different location

Classical School of Varation

Idea proposed by Muller that believed mutations were bad (deleterious) ; believed would be removed by purify selection

• Wild type is favored

Balance School of Varation

Idea proposed by T.Dobzhanky that believed there is alot of genetic variation within the genome ; would be maintain through balancing selection

• Heterozygous are favored