Heritability, Genetics, and Experience

How do genes affect behavior?

genetics → structure/function of the NS → how we perceive stimuli, process info, and respond to environment

What is Heritability?

An estimate of how much of the variance in a characteristic is due to differences in heredity (genes)

OR in a group of people, what is the contribution of genetic differences to phenotypic differences?

How do we study Heritability?

biochemical methods, twin studies, adoption studies

what are biochemical methods?

identification of certain genes linked to behaviors or disorders

what is the twin studies method?

where you pick a trait and see how often it is the same (concordant) in both twins.

compare the concordance in MONOZYGOTIC twins with the concordance in DIZYGOTIC twins.

What is the concordance of MZ > DZ ?

more shared genes and more shared traits = greater heritability

what is the concordance of MZ = DZ ?

difference in shared genes but not in shared trait = lower heritability

what is the adoption studies method?

choose a trait and see whether an adopted kid resembles biological parents more than adoptive parents (high heritability) or adopted kid is more like adoptive parents (low heritability)

what are the problems with studying twins and adoption?

prenatal & postnatal environments

describe the studies on maze-bright/dull rats

maze-dull and maze-bright rats are raised in enriched or impoverished environments.

maze-dull rats made more errors if they were raised in an impoverished environment.

describe the studies on human (twin) intelligence

intelligence develops as an interaction of inheritance and experience.

humans can inherit potential for greater intelligence but may not be realized in poverty-stricken environments.

describe the studies on PKU (a single-gene metabolic disorder)

it is an inherited inability to metabolize phenylalanine. it is mitigated (made less severe) entirely by a special diet in infancy and childhood (interaction between genetics & enviornment)

compare and contrast genetics and epigenetics

genetics: a gene → coding sequence of DNA

epigenetics: structure of the DNA → decides whether or not a gene is turned on (influenced by experience)

Define sex-limited genes

genes that are on the autosomal chromosomes and are activated/turned on under the influence of sex hormones (estrogen, testosterone…)

define sex-linked genes

genes on the sex chromosomes (X and Y) (X-linked genes). females have 2 copies of the X chromosome, males have 1 X and 1 Y

compare and contrast sex-limited and sex-linked genes

sex-linked genes are on the sex chromosomes (most are X-linked, most phenotypes seen in males more).

sex-limited genes are on the autosomal chromosomes (activated by sex hormones)

define transcription

the process of making mRNA from DNA.

a copy of genetic code from DNA → RNA.

occurs in the nucleus of a cell.

define translation

the process of making a protein from mRNA.

uses mRNA message to build specific protein.

occurs in the cytoplasm (ribosomes).

How do mRNA vaccines work?

it gives your cells the instructions (mRNA) to make a harmless piece of virus. your cells read this and make that protein that your immune system recognizes as foreign and learns to fight it. if the real virus enters, your immune system already knows how to fight it.

what are some epigenetic modifications that can occur?

methylation, acetylation, histone modifications

How does methylation affect gene activity?

it tightens DNA, which makes it harder to express a gene.

how does demethylation affect gene activity?

increase gene activity (becomes looser → gene more likely to be expressed)

how does acetylation affect gene activity?

increase gene activity (the proteins DNA wraps around loosens → easier for gene to be expressed)

what kinds of experiences can cause epigenetic modifications?

nutrition, drug exposure, health and disease

who can those epigenetic modifications effect?

the person in which it happens, their children, and potentially future generations