Chapter 3

Question 1

Union of sperm and ovum to produce a
zygote; also called conception.

Answer 1

fertilization

Question 2

One-celled organism resulting from
fertilization.

Answer 2

zygote

Question 3

Twins conceived by the union of two
different ova (or a single ovum that has
split) with two different sperm cells; also
called fraternal twins; they are no more
alike genetically than any other siblings.

Answer 3

dizygotic twins

Question 4

Twins resulting from the division of a
single zygote after fertilization; also
called identical twins; they are
genetically similar.

Answer 4

monozygotic twins

Question 5

Chemical that carries inherited
instructions for the development of all
cellular forms of life.

Answer 5

deoxyribonucleic acid (DNA)

Question 6

Sequence of bases within the DNA
molecule; governs the formation of
proteins that determine the structure
and functions of living cells.

Answer 6

genetic code

Question 7

Coils of DNA that consist of genes.

Answer 7

chromosomes

Question 8

Small segments of DNA located in definite
positions on particular chromosomes;
functional units of heredity

Answer 8

genes

Question 9

Complete sequence of genes in the
human body.

Answer 9

human genome

Question 10

Permanent alterations in genes or
chromosomes that may produce
harmful characteristics.

Answer 10

mutations

Question 11

In humans, the 22 pairs of chromosomes
not related to sexual expression.

Answer 11

autosomes

Question 12

Pair of chromosomes that determines
sex: XX in the normal human female,
XY in the normal human male.

Answer 12

sex chromosomes

Question 13

Two or more alternative forms of a gene
that occupy the same position on
paired chromosomes and affect the
same trait.

Answer 13

alleles

Question 14

Possessing two identical alleles for a trait.

Answer 14

homozygous

Question 15

Possessing differing alleles for a trait.

Answer 15

heterozygous

Question 16

Pattern of inheritance in which, when a
child receives different alleles, only the
dominant one is expressed.

Answer 16

dominant inheritance

Question 17

Pattern of inheritance in which a child
receives identical recessive alleles,
resulting in expression of a nondominant
trait.

Answer 17

recessive inheritance

Question 18

Pattern of inheritance in which multiple
genes at different sites on
chromosomes affect a complex trait.

Answer 18

polygenic inheritance

Question 19

Observable characteristics of a person.

Answer 19

phenotype

Question 20

Genetic makeup of a person, containing
both expressed and unexpressed
characteristics.

Answer 20

genotype

Question 21

Combination of genetic and
environmental factors to produce
certain complex traits.

Answer 21

multifactorial transmission

Question 22

Mechanism that turns genes on or off
and determines functions of body cells.

Answer 22

Epigenesis

Question 23

Pattern of inheritance in which a child
receives two different alleles, resulting
in partial expression of a trait.

Answer 23

incomplete dominance

Question 24

Pattern of inheritance in which certain
characteristics carried on the X
chromosome inherited from the mother
are transmitted differently to her male
and female offspring.

Answer 24

sex-linked inheritance

Question 25

Chromosomal disorder characterized by moderate-to-severe mental retardation and by such physical signs as a downwardsloping skin fold at the inner corners of the eyes. Also called trisomy-21.

Answer 25

Down syndrome

Question 26

Clinical service that advises prospective parents of their probable risk of having children with hereditary defects.

Answer 26

Genetic counseling

Question 27

Quantitative study of relative hereditary and environmental influences on behavior.

Answer 27

behavioral genetics

Question 28

Statistical estimate of contribution of heredity to individual differences in a specific trait within a given population.

Answer 28

heritability

Question 29

Term describing tendency of twins to share the same trait or disorder.

Answer 29

concordant

Question 30

Potential variability, depending on environmental conditions, in the expression of a hereditary trait.

Answer 30

reaction range

Question 31

Limitation on variance of expression of certain inherited characteristics.

Answer 31

canalization

Question 32

The portion of phenotypic variation that results from the reactions of genetically different individuals to similar environmental conditions.

Answer 32

genotype-environment interaction

Question 33

Tendency of certain genetic and environmental influences to reinforce each other; may be passive, reactive (evocative), or active. Also called genotype-environment covariance.

Answer 33

genotype-environment correlation

Question 34

Tendency of a person, especially after early childhood, to seek out environments compatible with his or her genotype.

Answer 34

niche-picking

Question 35

The unique environment in which each child grows up, consisting of distinctive influences or influences that affect one child differently than another.

Answer 35

nonshared environmental effects

Question 36

Extreme overweight in relation to age, sex, height, and body type as defined by having a body mass index at or above the 95th percentile.

Answer 36

Obesity

Question 37

Characteristic disposition, or style of approaching and reacting to situations.

Answer 37

Temperament

Question 38

Mental disorder marked by loss of contact with reality; symptoms include hallucinations and delusions.

Answer 38

schizophrenia

Question 39

Period of development between conception and birth.

Answer 39

Gestation

Question 40

Age of an unborn baby, usually dated from the first day of an expectant mother’s last menstrual cycle.

Answer 40

Gestational age

Question 41

The upper parts of the body develop before the lower parts of the trunk.

Answer 41

cephalocaudal principle

Question 42

The parts of the body near the center develop before the extremities.

Answer 42

proximodistal principle

Question 43

First 2 weeks of prenatal development, characterized by rapid cell division, blastocyst formation, and implantation in the wall of the uterus.

Answer 43

Germinal stage

Question 44

The attachment of the blastocyst to the uterine wall, occurring at about day 6.

Answer 44

Implantation

Question 45

Second stage of gestation (2 to 8 weeks), characterized by rapid growth and development of major body systems and organs.

Answer 45

embryonic stage

Question 46

Natural expulsion from the uterus of an embryo that cannot survive outside the womb; also called miscarriage.

Answer 46

spontaneous abortion

Question 47

Final stage of gestation (from 8 weeks to birth), characterized by increased differentiation of body parts and greatly enlarged body size.

Answer 47

Fetal stage

Question 48

Prenatal medical procedure using highfrequency sound waves to detect the outline of a fetus and its movements, so as to determine whether a pregnancy is progressing normally

Answer 48

Ultrasound

Question 49

Environmental agent, such as a virus, a drug, or radiation, that can interfere with normal prenatal development and cause developmental abnormalities.

Answer 49

Teratogen

Question 50

Combination of mental, motor, and developmental abnormalities affecting the offspring of some women who drink heavily during pregnancy

Answer 50

fetal alcohol syndrome (FAS)

Question 51

Viral disease that undermines effective functioning of the immune system.

Answer 51

acquired immune deficiency syndrome (AIDS

Question 52

Physical or psychological demands on a person or organism.

Answer 52

Stress