Chapter 2

Question 1

zygote

Answer 1

the new cell formed by the
process of fertilization.

Question 2

genes

Answer 2

the basic units of genetic
information.

Question 3

DNA molecules

Answer 3

the substance that genes are
composed of that determines the
nature of every cell in the body
and how it will function.

Question 4

chromosomes

Answer 4

rod-shaped portions of DNA that
are organized in 23 pairs.

Question 5

Why do multiple births occur?

Answer 5

1. Some occur when a cluster of cells in the ovum split off within the first two weeks.
2. More commonly, two separate ova are fertilized by two separate sperm at roughly the same time.

Question 6

monozygotic twins

Answer 6

twins who are genetically
identical.

Question 7

dizygotic twin

Answer 7

twins who are produced when
two separate ova are fertilized
by two separate sperm at roughly
the same time.

Question 8

dominant trait

Answer 8

the one trait that is expressed
when two competing traits are
present.

Question 9

recessive trait

Answer 9

a trait within an organism that is
present, but is not expressed.

Question 10

genotype

Answer 10

the underlying combination of
genetic material present (but not
outwardly visible) in an organism.

Question 11

phenotype

Answer 11

an observable trait; the trait that is
actually seen.

Question 12

homozygous

Answer 12

inheriting from parents similar
genes for a given trait.

Question 13

heterozygous

Answer 13

inheriting from parents different
forms of a gene for a given trait.

Question 14

polygenic inheritance

Answer 14

inheritance in which a
combination
of multiple gene
pairs is responsible
for the
production
of a particular trait.

Question 15

reaction range

Answer 15

the potential degree of variability in the actual expression of a trait due to environmental conditions.

Question 16

X-linked genes

Answer 16

genes that are considered
recessive
and located only on
the X chromosome.

Question 17

Huntington’s disease

Answer 17

Huntington gene localized to the terminal portion of the short arm of
chromosome 4.

Question 18

Obsessive-Compulsive
Disorder (OCD)

Answer 18

Several potentially relevant genes have been identified but additional research
is needed to verify.

Question 19

Fragile X mental retardation

Answer 19

Two genes identified.

Question 20

Early onset (familial)
Alzheimer’s disease

Answer 20

Three distinct genes identified. Most cases caused by single-gene mutation
on chromosomes 21, 14, and 1.

Question 21

Attention deficit hyperactivity
disorder (ADHD)

Answer 21

Evidence in some studies has linked ADHD with dopamine-receptor D4 and
D5 genes, but the complexity of the disease makes it difficult to identify a
specific
gene.

Question 22

Alcoholism

Answer 22

Research suggests that genes affecting the activity of the neurotransmitters
serotonin and GABA likely are involved in risk for alcoholism.

Question 23

Schizophrenia spectrum
disorder

Answer 23

There is no agreement, but links to chromosomes 1, 5, 6, 10, 13, 15, and
22 have been reported.

Question 24

behavioural genetics

Answer 24

the study of the effects of heredity
on behavior and psychological
characteristics.

Question 25

spontaneous mutation

Answer 25

when genes change their form for no known reason.

Question 26

Down syndrom

Answer 26

a disorder produced by the presence
of an extra chromosome on
the twenty-first pair; once referred
to as mongolism.

Question 27

fragile X-syndrome

Answer 27

a disorder produced by injury to a
gene on the X chromosome, producing
mild to moderate mental
retardation.

Question 28

sickle cell anemia

Answer 28

a blood disorder that gets its name
from the shape of the red blood
cells in those who have it.

Question 29

Tay-Sachs disease

Answer 29

a disorder that produces blindness
and muscle degeneration prior to
death; there is no treatment.

Question 30

Klinefelter’s disease

Answer 30

a disorder resulting from the presence
of an extra X chromosome
that produces underdeveloped
genitals, extreme height, and
enlarged
breasts.

Question 31

Genetic counselling

Answer 31

the discipline that focuses on
helping people deal with issues
relating
to inherited disorders.

Question 32

ultrasound sonography

Answer 32

a process in which high-frequency
sound waves scan the mother’s
womb to produce an image of
the unborn baby, whose size and
shape can then be assessed.

Question 33

chronic villus sampling (CVS)

Answer 33

a test used to find genetic defects
that involves taking samples of
hair-like material that surrounds
the embryo.

Question 34

first-trimester screening

Answer 34

Combines a blood test and
ultrasound
sonography in the eleventh to thirteenth week of pregnancy and can identify
chromosomal abnormalities and other disorders, such as heart problems.

Question 35

amniocentisis

Answer 35

the process of identifying genetic
defects by examining a small
sample
of fetal cells drawn by a
needle inserted into the amniotic
fluid surrounding the unborn
fetus.

Question 36

Currently available DNA based genetic tests

Answer 36

Alzheimer’s disease - Late-onset variety of senile dementia

Amyotrophic lateral sclerosis (Lou Gehrig’s
disease) - Progressive motor function loss leading to paralysis
and death

Breast and ovarian cancer (inherited) - Early-onset tumors of breasts and ovaries

Charcot–Marie–Tooth - Loss of feeling in ends of limbs

Cystic fibrosis - Thick mucus accumulations in lungs and chronic infections in lungs and pancreas

Duchenne muscular dystrophy (Becker muscular
dystrophy) - Severe to mild muscle wasting, deterioration,
weakness

Dystonia - Muscle rigidity, repetitive twisting movements

Fragile X syndrome - Mental retardation

Hemophilia A and B - Bleeding disorders

Hereditary nonpolyposis colon cancera - Early-onset tumors of colon and sometimes other organs

Huntington’s disease - Progressive neurological degeneration, usually beginning in midlife

Myotonic dystrophy - Progressive muscle weakness

Neurofibromatosis, type 1 - Multiple benign nervous system tumors that can be
disfiguring;
cancers

Phenylketonuria - Progressive mental retardation due to missing enzyme;
correctable
by diet

Sickle-cell disease - Blood cell disorder, chronic pain and infections

Spinal muscular atrophy - Severe, usually lethal progressive muscle-wasting disorder
in children

Tay-Sachs disease - Seizures, paralysis, fatal neurological disease of early
childhood

Question 37

preimplantation genetic diagnosis (PGD)

Answer 37

to ensure that their next child would be free of Fanconi anemia.
With PGD, a newly fertilized embryo can be screened for a variety of genetic diseases before
it is implanted in the mother’s uterus to develop

Question 38

germ line therapy

Answer 38

In which cells are taken from an
embryo and then replaced after the defective genes they contain have been repaired.

Question 39

temperament

Answer 39

patterns of arousal and
emotionality that represent
consistent and enduring
characteristics in an individual.

Question 40

multifactorial transmission

Answer 40

the determination of traits by a
combination of both genetic and
environmental factors in which
a genotype provides a range
within which a phenotype may
be expressed.

Question 41

Do we inherit our personality?

Answer 41

At least in part. There’s increasing research
evidence suggesting that some of our most basic personality traits have genetic roots.
For example, two of the key “Big Five” personality traits, neuroticism and extroversion,
have been linked to genetic factors. Neuroticism, as used by personality researchers,
is the
degree
of emotional stability an individual characteristically displays. Extroversion is the
degree to which a person seeks to be with others, to behave in an outgoing manner, and
generally to be sociable.

Question 42

What personality traits have high contributions of genes?

Answer 42

social potency (the tendency to
be a masterful, forceful leader who enjoys being
the center of attention) and traditionalism
(strict endorsement of rules and authority) are
strongly associated with genetic
factors.

Even less basic personality traits are linked
to genetics. For example, political attitudes,
religious
interests and values, and even attitudes
toward human sexuality have genetic components

Question 43

fertilization

Answer 43

the process by which a sperm and
an ovum—the male and female
gametes, respectively—join to
form a single new cell.

Question 44

germinal stage

Answer 44

the first—and shortest—stage of
the prenatal period, which takes
place during the first two weeks
following conception.

Question 45

placenta

Answer 45

a conduit between the mother and
fetus, providing nourishment and
oxygen via the umbilical cord.

Question 46

embryonic stage

Answer 46

the period from two to eight weeks
following fertilization during
which significant growth occurs
in the major organs and body
systems.

Question 47

ectoderm

Answer 47

The outer layer of the embryo which will form teeth, hair, skin, sense-organs, and the brain and spinal cord

Question 48

endoderm

Answer 48

The inner layer of the embryo which will produce the digestive system, liver, pancreas, and respiratory system.

Question 49

mesoderm

Answer 49

The layer between endoderm and exoderm. It will form muscles, bones, blood, and circulatory system.

Question 50

fetal stage

Answer 50

the stage that begins at about
eight weeks after conception, and
continues until birth.

Question 51

fetus

Answer 51

a developing child, from eight
weeks after conception until birth.

Question 52

infertility

Answer 52

the inability to conceive after 12
to 18 months of trying to become
pregnant.

Question 53

artificial insemination

Answer 53

a process of fertilization in which a
man’s sperm is placed directly into
a woman’s vagina by a physician.

Question 54

in vireo fertilization (IVF)

Answer 54

a procedure in which a woman’s
ova are removed from her ovaries
and a man’s sperm are used to fertilize
the ova in a laboratory.

Question 55

miscarriage

Answer 55

known as a spontaneous abortion—
occurs when pregnancy ends before the developing child is able to survive outside the
mother’s womb. The embryo detaches from the wall of the uterus and is expelled.

They are usually attributed to some sort of genetic abnormality

Question 56

abortion

Answer 56

when the mother voluntarily chooses to terminate the pragnency.

Question 57

teratogen

Answer 57

an environmental agent that
produces
a birth defect.

Question 58

Fetal alcohol spectrum disorder (FASD)

Answer 58

a disorder caused by the pregnant
mother consuming substantial
quantities of alcohol during
pregnancy,
potentially resulting
in mental retardation and delayed
growth in the child.

Question 59

fetal alcohol effects (FES)

Answer 59

a condition in which children
display some, though not all,
of the problems of fetal alcohol
syndrome due to the mother’s
consumption of alcohol during
pregnancy.