Chapter 2 - Genetic Bases of Childhood Development

Question 1

Why do relatively few genetic disorders involve dominant alleles?

Answer 1

inherited disorders are rarely carried by dominant alleles because individuals with such a disorder usually don’t live long enough to have children

Question 2

alleles

Answer 2

a variation of a specific gene

Question 3

Define: sickle-cell trait

Answer 3

disorder in which individuals show signs of mild anemia only when they are seriously deprived of oxygen; occurs in individuals who have one dominant allele for normal blood cells and one recessive sickle-cell allele

Question 4

Define: sex chromosomes

Answer 4

the 23rd pair of chromosomes; these determine the sex of the child

Question 5

Define: recessive

Answer 5

an allele whose instructions are ignored when it is combined with a dominant allele

Question 6

Define: polygenic inheritance

Answer 6

when phenotypes are the result of the combined activity of many separate genes

Question 7

Define: phenotype

Answer 7

the physical, behavioural, and psychological features that are the result of the interaction between one’s genes and the environment

Question 8

Define: niche-picking

Answer 8

the process of deliberately seeking environments that are compatible with one’s genetic makeup

Question 9

Define: autosomes

Answer 9

the first 22 pairs of chromosomes, the chromosomes in each pair are about the same size

Question 10

Define: behavioural genetics

Answer 10

the branch of genetics that deals with inheritance of behavioral and psychological traits

Question 11

Define: chromosomes

Answer 11

tiny structures in the nucleus that contain genetic material

Question 12

Define: deoxyribonucleic acid—DNA

Answer 12

a molecule composed of four nucleotide bases; the biochemical basis of heredity.

Question 13

Define: dizygotic twins

Answer 13

twins from two separate eggs fertilized by two separate sperm, genetically, fraternal twins are just like any other siblings, on average, about half their genes are the same

Question 14

Define: dominant

Answer 14

the form of an allele whose chemical instructions are followed

Question 15

Define/explain: Trisomy 21 aka Down Syndrome

Answer 15

a genetic disorder that is caused by an extra 21st chromosome

Question 16

Define: epigenesis

Answer 16

continuous interplay between genes and multiple levels of the environment (from cells to culture) that drives development

Question 17

Define: gene

Answer 17

a group of nucleotide bases that provide a specific set of biochemical instructions

Question 18

Define: genotype

Answer 18

the complete set of genes that makes up a person’s heredity

Question 19

Define: monozygotic twins

Answer 19

identical twins, come from a single fertilized egg that split in two, have identical genes

Question 20

Define: incomplete dominance

Answer 20

the situation in which one allele does not dominate another completely

Question 21

Define/explain: in vitro fertilization

Answer 21

mixing sperm and egg together in a laboratory dish and then placing several fertilized eggs in a woman’s uterus

Question 22

Define: heritability coefficient

Answer 22

the extent to which differences between people reflect heredity

Question 23

Define: homozygous

Answer 23

a person who inherits the same allele on a pair of chromosomes, the biochemical instructions on the allele are followed

Question 24

Define: Huntington’s disease

Answer 24

a type of dementia caused by a dominant allele; characterized by degeneration of the nervous system

Question 25

Define: heterozygous

Answer 25

a person who inherits different alleles, the instructions of the dominant allele are followed, those of the recessive allele are ignored

Question 26

Define: nonshared environmental influences

Answer 26

forces within a family that make children different from one another

Question 27

What fraction of attempts at in vitro fertilization succeed?

Answer 27

only about one-third of the attempts at in vitro fertilization succeed

Question 28

How many sperm are contained in a teaspoon of ejaculate?

Answer 28

from 200 million to 500 million sperm

Question 29

A child’s 46 chromosomes include approximately how many thousand genes?

Answer 29

a child’s 46 chromosomes include about 25,000 genes, chromosome 1 has the most genes (nearly 3,000) and the Y chromosome has the fewest (just over 200)