Chapter 4 (Module 4.1) - Genetics and Evolution of Behavior

Question 1

this term refers to units of heredity that maintain their structural identity from one generation to another

Answer 1

genes

Question 2

what does a dominant gene mean?

Answer 2

a dominant gene shows a strong effect in either the homozygous or heterozygous condition

Question 2

what does DNA stand for?

Answer 2

deoxyribonucleic acid

Question 2

what are enzymes?

Answer 2

enzymes are biological catalysts that regulate chemical reactions in the body

Question 2

what are chromosomes?

Answer 2

chromosomes are strands of genes

Question 2

what are the four “bases” of DNA?

Answer 2

1. Adenine
2. Guanine
3. Cytosine
4. Uracil

Question 2

what serves as the template for the synthesis of protein molecules?

Answer 2

messenger RNA

Question 3

what does it mean if you are homozygous for a gene?

Answer 3

you have the same genes on your two copies of some chromosome

Question 3

what does it mean if you are heterozygous for a gene?

Answer 3

it means you have an unmatched pair of genes

Question 4

what does a recessive gene mean?

Answer 4

a recessive gene shows its effects only in the homozygous condition

Question 5

Suppose you have high sensitivity to tasting PTC.

If your mother can also taste it easily, what (if anything) can you predict about your father’s ability to taste it?

Answer 5

If your mother has high sensitivity to the taste of PTC, we can make no predictions about your father.

You may have inherited a high-sensitivity gene from your mother, and because the gene is dominant, you need only one copy of the gene to taste PTC

Question 6

Suppose you have high sensitivity to the taste of PTC.

If your mother has low sensitivity, what (if anything) can you predict about your father’s taste sensitivity?

Answer 6

If your mother has low sensitivity, you must have inherited your high-sensitivity gene from your father, so he must have high sensitivity

Question 6

Suppose someone identifies a “gene for” certain aspects of development.

How might that statement be misleading?

Answer 6

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

Question 7

what are the genes the sex chromosomes known as?

Answer 7

sex-linked genes

Question 8

what are sex-limited genes?

Answer 8

genes that are present in both sexes but active mainly in one sex

Question 8

what are autosomal genes?

Answer 8

genes that are not on a sex chromosome and is on a numbered chromosome

Question 9

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

Answer 9

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

Question 9

what is a mutation?

Answer 9

a heritable change in a DNA molecule

Question 10

what are epigenetics

Answer 10

a field of study that deals with changes in gene expression

Question 11

How does an epigenetic change differ from a mutation?

Answer 11

A mutation is a permanent change in part of a chromosome.

An epigenetic change is an increase or decrease
in the activity of a gene or group of genes

Question 11

what are histones?

Answer 11

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

Question 11

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

Answer 11

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

Question 12

what does dizygotic mean?

Answer 12

from two eggs

Question 12

what does monozygotic mean?

Answer 12

from one egg

Question 13

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

Answer 13

One type of evidence is greater similarity between monozygotic twins than dizygotic twins. Another is resemblance between adopted children and their biological parents. A third is a demonstration that a particular gene is more common than average among people who show a particular behavior

Question 13

Suppose someone determines the heritability of IQ scores for a given population. Then society changes in a way that provides the best possible opportunity for everyone within that population. Will heritability of IQ increase, decrease, or stay the same?

Answer 13

Heritability will increase. Heritability estimates how much of the variation is due to differences in genes. If everyone has the same environment, then differences in environment cannot account for much of the remaining differences in IQ scores. Therefore, the relative role of genetic differences will be greater.

Question 14

what is evolution?

Answer 14

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

Question 14

what is phenylketonuria?

Answer 14

a genetic inability to metabolize the amino acid phenylalanine

Question 14

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

Answer 14

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

Question 15

what is Lamarckian evolution?

Answer 15

the inheritance of acquired characteristics

Question 16

what does fitness mean? for genetics

Answer 16

it is operationally defined as the number of copies of one's genes that endure in later generations

Question 17

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

Answer 17

No. Failure to need a structure does not make it smaller in the next generation. The appendix will shrink only if people with a gene for a smaller appendix reproduce more successfully than other people do.

Question 18

what is kin selection?

Answer 18

selection for a gene that benefits the individual's relatives

Question 19

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

Answer 19

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.