Lecture 7: Non-Mendelian inheritance Part II

Complex (quantitative) traits

Are controlled by multiple genes (polygenic inheritance), often influenced by the environment, show continuous variation

example of complex (quantitative) traits

human height (controlled by many genes, influenced by environment, show continuous variation)

multigenic (polygenic) inheritance

Multiple genes each contribute a small, additive effect to the phenotype, no single gene determines the trait, individual alleles usually have incomplete dominance effects.

example of multigenic (polygenic) inheritance

human skin color (determined by multiple genes)

maternal (cytoplasmic) inheritance

Organelle (e.g., chloroplasts) genomes are often inherited from mom

cellular explanation for maternal inheritance

Eggs (not sperm) provide most of the zygote’s cytoplasm

X-inactivation

when one of two X chromosomes is silenced in females (in XX/XY and XX/X0 systems), achieves dosage compensation

epigenetic inheritance

changes in gene expression without changing the DNA sequence

Genomic imprinting

gene expression only occurs from the genetic material from one parent

dosage compensation

balances gene expression from sex chromosomes between sexes