genetics and heritability

Mitosis

one cell divides into two identical daughter cells (body cells), aka we start as one cell and split to become millions

Meiosis

Sexual cell division—Four genetically unique gamete cells, chromosomes are reduced by half

crossing over

homologous chromosomes exchange genetic material during meiosis

locus

position of gene on chromosome

genome

complete set of an organism’s genes

genotype

inherited genetic material

phenotype

observable expression of gemotype

regulator genes

control the switching on & off of genes—chain reaction + network

allele

2+ different forms of a gene (dominant allele or recessive allele)

homozygous

same alleles are inherited (CC or cc)

heterozygous

different alleles are inherited (Cc or cC)

intermediate heterozygous

in between--wavy hair

combined heterozygous

both-curly and straight hair

dominance heterozygous

only reflects dominant gene

genomic imprinting

rare heterozygous result where only one copy of a gene is expressed, either from the mother or the father

PKU

disorder caused by recessive gene. results in a missing enzyme and has damaging effects on the CNS

down syndrome

trisomy 21-extra 21st chromosome due to failure of chromosome separation

Klinefelter Syndrome

XXY (male)—low testosterone, some hips and breasts, normal IQ

Turner Syndrome

(45, x)- missing second X. Normal IQ, sometimes nonverbal

Behavioral Genetics

extent to which genes and environment contribute to individual differences

polygenetic

multifactorial (multiple genes and environments)

heritability

how much the measured variance of individuals in a given environment is attributable to genetic differences among those individuals AKA the proportion of variability in behavior that can be attributed to environmental factors

heritability equation

H²=genetic variance/genetic var+env. var. Ranges from 0 to 1—closer to 1 means very much due to genetics, far from 1 means genes don’t matter

Heritability Example

heritability of height = 0.8, genes account for 80% of the variation of height in a population

Family Study

family members should be more genetically related than unrelated individuals—how characteristics are shared among family members

monozygotic twins

egg splits--twins share 100% of the same DNA. only difference between them is their environment

dizygotic twins

mom double ovulates (2 eggs), they are just like any other siblings. 50% of genes in common

genotype-environment correlation

genes affecting the environment one experiences

genotype-environment interactions

effect of genes depends on the environment and vice versa (ex: genetic preposition for depression but it onky develops if traumatic event is experienced)

passive gene-environment correlation

parents pass on both genes and environment (child has no role)

active gene-environment correlation

people seek out environments that match their genetic tendencies

evocative or reactive gene-environment correlation

traits evoke certain responses from others (naturally cheerful temperament receives positive treatment from teachers)

genome wide association study

identify genetic variants associated with traits using SNPs. Can only measure association, not causation

SNP

single base-pair variation in DNA sequence that causes genetic variation, like T1D

genome wide complex trait analysis

how much of the variation in a complex trait is explained by all SNPs (overall genetic contribution of SNPs)

epigenesis

the environment or context can influence the genetic expression of genes

Methylation

adding a methyl group to DNA, altering gene expression (on and off, hormone production, etc)