Epigenetics

Phenotype: result of gene expression May be easily observable traits Shape Size Color

Phenotype May require a special test to observe Blood type in humans Hip joint stability in dogs

What’s the Phenotype? More than one trait can be observed!

What’s the Phenotype? Color Shape of ears Length of hair Herding instinct

Phenotype results from Genes Genes are the instructions for phenotype; called genotype You get genes from your parents You therefore resemble your parents

Phenotype is not all caused by the genes Epigenetics: environment influences genes Internal Environment – cell contents and neighbors External environment – outside the body

Internal Factors Earliest cells are totipotent (able to become anything) As time passes, they become limited in what they can produce

Cloning Convince a totipotent cell that it is an embryo by transplanting the totipotent cell’s nucleus into an ova without a nucleus Result: copy of donor [some differences affecting aging]

Cloning

Clones also happen naturally…same DNA

Clones are NOT identical! Rainbow & CC

As the embryo ages, some genes are turned OFF. Rainbow could express both orange and grey fur, but CC only expresses grey. In females, one X chromosome is deactivated early in embryonic development. Similarly, embryonic cells develop limits for their fate.

Different portions of the Embryo have different Fates Fate Maps – show what portion of a zygote becomes what portion of the embryo (or placenta)

Ligers and Tigons Hybrids, so usually sterile Effect of egg protein is visible Liger: male lion and female tiger Typically much larger than either parent Tigon: male tiger and female lion Often smaller than both parents

Liger

Pleuripotent: can become many types of cell, but not all

Transplants and Grafts

Could be useful for humans

Other Cells influence gene expression Affect whether mitosis happens Affect which genes are expressed

Environment influences Phenotype Accident, disease, and other factors can change phenotype

Environment influences Phenotype Accident, disease, and other factors can change phenotype

A Few Classic Examples Bees: Royal Jelly transforms larvae into Queens Fertile; larger abdomen Unbarbed stinger

http://pheylonian.com/photos/custom/bee-sizes-queen-drone-worker.png

Crocodiles Egg incubation temperature causes gender

An example in Humans Poor diet can lead to people being stunted - smaller than their genes’ instructions