neurophysiological psychology chapter four textbook

genes

units of heredity

chromosomes

strands of genes that come in pairs

deoxyribonucleic acid (DNA)

double-standed molecule

*serves as a template for RNA

ribonucleic acid (RNA)

single-stranded molecule

*serves as a template for the synthesis of protein molecules

four DNA bases

adenine, guanine, cytosine, thymine

four RNA bases

adenine, guanine, cytosine, uracil

Any protein consists of some combination of ____ amino acids.

20

enzymes

biological catalysts that regulate chemical reactions in the body

homozygous

same gene for both chromosomes

rr, RR

heterozygous

unmatched pair of genes

Rr

genes can be:

• dominant

• recessive

• intermediate

dominant gene

exerts strong effect in either the homozygous or heterozygous condition

recessive gene

exerts its effects only in homozygous cindition

Suppose you have high sensitivity to tasting PTC. If one of your parents can also taste it easily, what (if anything) can you predict about your other parent’s ability to taste it?

If one parent has high sensitivity to the taste of PTC, we can make no predictions about the other parent. You may have inherited a high-sensitivity gene from one parent, and because the gene is dominant, you need only one copy of the gene to taste PTC

Suppose you have high sensitivity to the taste of PTC. If one of your parents has low sensitivity, what (if anything) can you predict about your other parent’s taste sensitivity?

If one parent has low sensitivity, you must have inherited your high-sensitivity gene from the other parent, who must have high sensitivity.

Why is it misleading to talk about “a gene for” some characteristic?

Almost any characteristic depends on more than one gene, as well as influences from the environment.

sex-linked genes

genes on sex chromosomes (x and y)

autosomal genes

all other chromosomes (than sex chromosomes)

sex-limited genes

present in both sexes but active mainly in one sex

(ex: chest hair, breast size, amount of crowing in roosters, rate of egg production in hens)

Both sexes have the genes, but ___ ______ activate them in one sex and not the other, or one sex more than the other. Many sex-limited genes show their effects at puberty.

sex hormones

How does a sex-linked gene differ from a sex-limited gene?

A sex-linked gene is on the X or Y chromosome.
A sex-limited gene is on an autosomal chromosome, but hormones activate it in one sex more than the other.

mutation

heritable change in DNA molecule

genetic changes occur through

• mutation

• duplication

• deletion

epigenetics

field that deals w/ changes in gene expression

histones

proteins that bind DNA into shape that is more like string wound around balls

Many experiences can alter the chemistry of the brain in a way that ________ some genes and ______ others.

activates; inactivates

How does an epigenetic change differ from a mutation?

A mutation is a permanent change in part of a chromo- some. An epigenetic change is an increase or decrease in the activity of a gene or group of genes.

How does adding a methyl or acetyl group to a histone protein alter gene activity?

Adding a methyl group turns genes off. An acetyl group loosens histone’s grip and increases gene activation

heritability

variation depends highly on genetic differences

monozygotic twins

from one egg

dizygotic twins

from two eggs

About the only behavior that has not shown a significant heritability is _____ ________, such as Protestant or Catholic

religious affiliation

What are the main types of evidence to estimate the heritability of some behavior?

The main evidence is greater similarity between monozygotic twins than dizygotic twins. Another is resemblance between adopted children and their biological parents

If every child had an equally good environment, would heritability of IQ scores increase or decrease? If every child had an equally bad environment, would heritability increase or decrease?

If the quality of the environment is equal for all, heritability will increase, regardless of whether the environment is equally good or equally bad. If everyone has the same environment, whatever variation still exists would have to be due to heredity

What would be the heritability of having two arms? High or low?

The heritability is almost zero. You may be surprised, because having two arms is obviously under genetic control. However, heritability measures how much the variation in some feature depends on variation in genetics. Nearly all the variation in having two arms or having fewer depends on amputations (under the control of the environment) and not on any variation in genetics.

Even a trait with _____ heritability can be modified by ___________ interventions.

high; environmental

phenylketonuria

genetic inability to metabolize the amino acid phenylalanine

What example illustrates the point that even if some characteristic is highly heritable, a change in the environment can alter it?

Keeping a child with the PKU gene on a strict low- phenylalanine diet prevents the cognitive deficits that the gene ordinarily causes. The general point is that sometimes a highly heritable condition can be modified environmentally

A gene can influence brain ______, but it can influ- ence behavior even without being _____ in the brain.

development; expressed

evolution

change over generations in the frequencies of various genes in a population

artificial selection

choose individuals w/ desired trait + make them parents of next generation

*ex: racehorses

Lamarckian evolution

theory of evolution in which inheritance of acquired characteristics

ex: if you exercise your muscles, your children will be born w/ bigger arm muscles

*no evidence that this occurs

fitness

the number of copies of one’s genes that endure in later generations

*evolution, by definition, improves this

Many people believe the human appendix is useless. Will it become smaller and smaller with each generation?

No, the appendix will shrink only if people with a gene for a smaller appendix reproduce more successfully than other people do.

evolutionary psychology

concerns how behaviors evolved; emphasizes evolutionary + functional explanations of how our genes reflect those of our ancestors and why natural selection might have favored genes that promote certain behaviors

altruistic behavior

an action that benefits someone other than the actor

kin selection

selection for a gene that benefits an individual’s relatives

reciprocal altrusim

idea that individuals help those who will probably return the favor

group selection

altruistic groups thrive better than less cooperative ones

What are plausible ways for possible altruistic genes to spread in a population?

Altruistic genes could spread because they facilitate care for one’s kin or because they facilitate exchanges of favors with others (reciprocal altruism). Group selection may also work under some circumstances, especially if the cooperative group has a way to punish or expel an uncooperative individual.