Neural Development Flashcards
Genes
- Units of heredity that maintain their structural identity from one generation to another
- As a rule, genes come in pairs because they are aligned along chromosomes (strands of genes) that also come in pairs
Homozygous
-If you have the same genes on your two copies of some chromosome, you are homozygous for that gene
Heterozygous
-If you have an unmatched pair of genes, you are heterozygous for that gene
Dominant gene
-Shows a strong effect in either the homozygous or heterozgyous condition
Recessive gene
-Shows its effect only in the homozygous condition
Sex-linked genes
-Are the genes on the sex chromosomes designated X and Y
Autosomal genes
-All other chromosomes that aren’t X or Y are called autosomal chromosomes
Sex-limited genes
- Genes that are present in both sexes but that exert their effects primarily in one sex because of activation by androgens or estrogens
- Examples are the genes that control the amount of chest hair in men, breast size in women, amount of crowing in roosters, and rate of egg production in hens
Epigenetics
- A field that deals with changes in gene expression without modification of the DNA sequence
- Epigenetic changes can be inherited, at least for a generation or two
Histones
- Proteins called histones bind DNA into a shape that is more like string wound around a ball
- The histone molecules in the ball have loose ends to which certain chemical groups can attach
- To activate a gene, the DNA must partially unwind from the histones
Adding or removing an Acetyl group to histone tails does what?
- Adding an acetyl group to histone tails causes the histones to loosen their grip on the DNA, and therefore facilitates expression of that gene
- Removing an acetyl group from histone tails causes them to tighten their grip on the DNA, and therefore turns the gene off
Add or removing a methyl group to histone tails does what?
- Methyl groups are usually added or removed at the promoter regions of the beginning of a gene
- Adding methyl groups (CH3) to a promoter turns OFF a gene
- Removing a methyl group from a promoter turns ON a gene
Heritability
- Estimate of the degree to which variation in a characteristic depends on genetic variations in a given population
- Heritability ranges from zero, indicating no genetic contribution to the variation, to one, indicating complete control
- Remember, any estimate of heritability applies only to a particular population at a particular time
What 3 ways do researchers use to determine the heritability of a characteristic?
- Twin studies:
- Monozygotic twin studies = from one egg
- Dizygotic twin studies = from two eggs
- “Virtual twin” studies = children of the same age, adopted at the same time into a single family - Adoption studies
- Candidate gene approach
Proliferation
-The production of new cells