Animal Phys Lecture 6 Epigenetics

Phenotypic Plasticity

The ability of a single animal-with a fixed genotype- to express two ore more genetically controlled phenotypes

Phenotypic plasticity is carried out through…

One gene type, multiple phenotypes or by the environment

Adaptive response

How adaptations of the past are responsible for patterns of the phenotypic plasticity today (like how mussel shells are thicker in the presence of crabs)

Chemical/physical necessity

The forced pattern of an individual (like how rats who have a low protein diet will lead to poor performance in a maze)

Polyphenism

Outputs aren’t continuous, but rather discrete, resulting in several distinct phenotypes from the same genetic background (distinct morphology)

Polygenetic inheritance

How in Daphnia identical individuals can assume 2 or more distinct body forms based on the environment (helmet/larger exoskeleton)

Seasonal inheritance

How in butterflies identical individuals can assume 2 or more distinct body forms based on the season when they developed (coloring for thermoregulation)

Epigenetics

Modifications that do not change DNA sequence but affect which genes are expressed that are transmitted when genes replicate (can be environmentally induced and passed on)

DNA methylation

Covalent bond of a methyl group attached to cytosine residue, often at promoter (repression expression of gene) and transferred to daughter cells via DNA methyltransferase

Covalent modification of histone proteins

DNA wrapped around histones and the modification (tighter or looser) alters transcription (usually through methylation, acetylation or phosphorylation)

What are the two types of Epigenetic markers?

DNA methylation and covalent modification of histone proteins

Tissues usually have this pattern of gene expression

Consistent-tissue specific pattern

When do epigenetic markings take place?

During early stages of development and plays a key role in defining, establishing and maintaining cell lineages

Honeybees

DNA methylation can cause a worker bee to become a queen

Carpenter ants

Castes differ in brain histone acceleration

Mitotic/somatic inheritance

Somatic cell DNA tag inherited by other somatic daughter cells

Meiotic/transgenerational

Somatic cell DNA tag inherited by reproductive cells; sperm or egg (how mice and plants can be subjected to toxic agents)

Top-down order of study

Starting from an animal behavior and working down to find the root of why they act like that (to the genetic makeup)

Bottom-up order of study

Starting with the genetic makeup of an organism and working up towards knowing the tissue function and learning how is animal function going to be affected if its genes are changes