BIO130 - Exam 3 - Lecture 4

Non-Mendelian Inheritance

Polygenic Inheritance

Phenotype is the result of two or more genes
Leads to continuous variation (a range of values)

ie. human skin tone

Incomplete Dominance

Heterozygotes are intermediate in appearance between the two homozygotes

Codominance

Complete and simultaneous expression of both alleles in a heterozygote

Multiple Alleles

More than two

Ie. ABO blood types in humans (3 alleles, O is recessive, AB are codominant

Recessive Lethal

An allele that is lethal only when homozygous

May not have an effect on phenotype if heterozygote

X-linked Traits

Gene located on x chromosome

XY individuals are more likely to have trait - they only have one copy of the gene

Sex chromosomes

X chromosome: has many genes that are required for life

Y chromosome: no genes required for life

Epistasis

An interaction between genes such that one gene controls the expression of another gene

Ie. brown/black coated mice, separate gene controls whether the color is expressed or if they are albino

DNA

Is made of nucleotidesN

Nucleotides

5 carbon sugar, phosphate group and nitrogenous base

Nitrogenous Bases

Adenine, Guanine, Cytosine, Thymine (A-T) (C-G)

Double helix

Two strands of DNA, help together by H-bonds between bases

DNA Strands Antiparallel

Runs from 5’ to 3’ in opposite directions in the double helix.