lecture 13 - Phenotypic variation and inheritance

Describe inheritance?

• Some traits are heritable - passed on from one generation to the next

• Heredity - phenomenon which offspring resemble their parents

• Variation - why offspring are not identical

What are the principles of heredity?

• Inherited characteristics determined by genes

• All individuals of the same species have the same base set of genes

• Variants of the same gene - alleles - account for the variant traits

Describe genotype and phenotype?

• Genotype - organisms internal genetic code

• AA (dominant homozygote), or aa (recessive homozygote) to Aa (heterozygote)

• Phenotype - physical or observable expression of code

How do we get different alleles of genes?

• Changes in genotype arise from mutation of DNA

• Point mutations - single nucleotide changes

• Insertions or deletions

• Translocations, deletions or duplications - large scale chromosomal changes

• Mutations can be in the coding region or non coding region

Describe the causes of mutation?

Spontaneous mutations results from internal cellular processes

• mis incorporations of nucleotides during DNA replication

• Errors during meiosis

Induced mutations result from external mu ages

• UV light, chemicals

Describe mutation outcomes?

• Loss of function - interfere with ability of gene to code for a fully functioning protein

• Gain of function - result in a protein with altered functionality

• Silent mutation - no affect on protein

Describe somatic vs germ line mutations?

• Somatic mutations occur in soma, cells of the body not involved in sex cells

• Germline mutations happen in germ (sex cells), therefore inherited

Describer further sources of genetic variation?

• Reproduction

• Bacteria

Describe variation in bacteria?

• Bacteria genetically variable

• Mutations and rapid reproduction

• Horizontal DNA transfer

Describe horizontal DNA transfer?

• 3 ways

• Conjugation - transfer by direct cell to cell contact

• Transformation - uptake incorporation of naked DNA

• Transduction - transfer of chromosomal from cell to cell by bacteria

Describe transposing mediated DNA transfer?

• Are lengths of DNA that jump from one site to another

• Can integrate into DNA

• Can cut themselves out of DNA

• Can reintegrate elsewhere

• Contains genes that encode resistance to antibiotics