Figure 29.2
Use Figure 29.2 to answer the following:
54)
Are there any afflicted females?
54)
55)
Identify, by numbers, any other possible carriers.
55)
56)
Describe briefly the three mechanisms that lead to genetic variability.
56)
Among members of the Fuzzy Wuzzy tribe, we will consider two pairs of genes: F = fuzzy hair vs. f = straight hair, and T =
long hair vs. t = short hair. A homozygous, straight–shorthaired male marries a homozygous, fuzzy–longhaired female (P1
generation). Their offspring (the F1 generation) intermarry and produce progeny (second generation) of four types:
fuzzy–longhaired, fuzzy–shorthaired, straight–longhaired, and straight–shorthaired. The results follow a standard dihybrid
pattern.
57)
A cross of two second–generation, straight–shorthaired individuals would yield what
phenotype?
57)
58)
What is (are) the phenotype(s) of the first–generation offspring?
58)
TRUE/FALSE. Write ‘T’ if the statement is true and ‘F’ if the statement is false.
59)
Hemophilia is an X–linked condition caused by a recessive gene.
59)
60)
When two genes are on the same chromosome, they are considered linked.
60)
61)
Some segments of the Y chromosome have no counterpart on the X chromosome.
61)
62)
Environmentally produced phenotypes that mimic conditions that may be caused by genetic
mutation are called phenocopies.
62)
63)
Mitochondrial genes are free of errors. As a result, all genetic problems are due exclusively to
nuclear genes.
63)
64)
Down syndrome is an example of nondisjunction of chromosomes.
64)
65)
Genetic variation results from the crossing over and exchange of chromosomal parts that occur
during meiosis II.
65)
A cross of two second–generation, straight–shorthaired individuals would yield a
66)
It is possible for a baby to have type O blood if neither parent is type O.
66)
67)
Genetic segregation implies that the members of the allele pair determining each trait are
distributed to different gametes during mitosis.
67)
68)
The expression of all physical traits is strictly due to the inheritance of specific genes.
68)
69)
In incomplete dominance, the heterozygote has a phenotype intermediate between that of
homozygous–dominant and homozygous–recessive individuals.
69)
70)
Hereditary characteristics are transmitted to offspring by genes.
70)
71)
Delayed action genes can result in fatal diseases.
71)
72)
A Punnett square is a diagram that may be used to figure out the possible combinations of genes
for a trait.
72)
73)
The term lethal dominant gene indicates that the gene causes death only when the individual is
homozygous.
73)
74)
Alleles may code for alternative expressions of a genetic trait.
74)
75)
The same allele can have a different effect depending on which parent it comes from.
75)
76)
Most genetic disorders are inherited through dominant genes.
76)
77)
Normal vision is dictated by autosomal dominant genes.
77)
78)
Small RNAs control the timing of programmed cell death during development.
78)
MATCHING. Choose the item in column 2 that best matches each item in column 1.
Match the following:
79)
Situation in which an individual has
identical alleles for a particular trait.
A)
Homozygous
79)
Match the following:
80)
A condition of drier excessively sticky
mucus production.
B)
81)
An unremitting, fatal nervous system
disease involving degeneration of the
basal nuclei.
82)
A disorder of brain lipid metabolism.
A)
Huntington’s disease
C)
Cystic fibrosis
80)
81)
82)
Match the following:
83)
Means by which genes trade places,
some maternal and some paternal on
each chromosome.
84)
Results in chromosomes that have
mixed contributions from each parent.
A)
Chromosome crossover
B)
Gene recombination
83)
84)
Match the following:
85)
Situation in which an individual has
different alleles making up the
genotype for a particular trait.
A)
Heterozygous
85)
Match the following:
86)
Inheritance that results in continuous
or qualitative phenotypic variations
between two extremes; an example is
skin color.
A)
Polygenic inheritance
86)
87)
The dominant gene is expressed when
present; the recessive gene is
expressed only in the absence of the
dominant gene.
A)
Dominant–recessive inheritance
87)
Match the following:
88)
Actual genetic makeup.
A)
Genotype
88)
Match the following:
89)
Inherited traits determined by genes
on the X or Y chromosomes.
A)
Sex–linked inheritance
89)
Match the following:
90)
A chromosome pair that may be very
different in size.
A)
Sex chromosomes
90)
Match the following:
91)
A particular gene’s allele received by a
gamete has no influence over selection
of a different gene’s allele.
A)
Independent assortment
91)
Match the following:
92)
Chromosomes regulating most body
characteristics.
93)
Genes for the same trait that have
different expressions.
A)
Autosomes
92)
93)
Match the following:
94)
Rare type of dwarfism resulting from
an impaired ability of the fetus to
lengthen long bones by endochondrial
ossification.
A)
Achondroplasia
94)
Match the following:
95)
The gene allele that suppresses or
masks the expression of the other
allele.
A)
Dominant
95)
Match the following:
96)
Genes not expressed unless they are
present in homozygous condition.
A)
Recessive
96)
Match the following:
97)
Distribution of chromosomes to
different gametes.
A)
Chromosome segregation
97)
Match the following:
98)
Inheritance of the ABO blood group
type is an example of this type of
inheritance.
99)
The heterozygote has a phenotype
intermediate between those of the
homozygous dominant and
homozygous recessive.
A)
Incomplete dominance
B)
Multiple–allele inheritance
98)
99)
Match the following:
100)
Lack of skin pigmentation.
A)
Albinism
100)
ESSAY. Write your answer in the space provided or on a separate sheet of paper.
101)
In humans, farsightedness is inherited by possession of a dominant gene. If a man who is homozygous for
normal vision (aa) marries a woman who is heterozygous for farsightedness, what proportion of their children
would be expected to be farsighted?
102)
Suppose an XcXc female marries an XcY man. (a) What is the probability of producing a color–blind son? (b)
What is the probability of producing a color–blind daughter? (c) What is the probability of producing a
daughter who is a carrier for the color–blind gene? (d) What is the probability of having four sons in a row?
103)
A nurse is providing genetic counseling to a couple who both have the sickle–cell anemia trait, but not the
disease. The couple is trying to decide whether or not to have a child. What is the possibility that a child would
inherit the disease? What is one reason they might consider not having a child?
104)
A 40–year–old pregnant woman is concerned about possible genetic defects in her unborn fetus. Her physician
recommends prenatal testing and advises her of two methods. Compare and contrast amniocentesis with
chorionic villus sampling relative to the time each can be performed, and the relative advantages and
disadvantages of each.
105)
Assume that brown eyes (B) are dominant over blue (b); and right–handedness (R) is dominant over
left–handedness (r). A brown–eyed, right–handed man marries a blue–eyed, right–handed woman. Their first
child is brown–eyed and right–handed, and their second child is blue–eyed and left–handed. What are the
genotypes of the parents?
106)
Jane and Allen have just discovered that their son is a hemophiliac. Neither of them has hemophilia, and Allen
claims that no such condition was ever expressed in his family. Jane was told that her father was a hemophiliac
and that problems resulting from this condition caused his death. Allen has also been told that hemophilia can
only be passed on to an offspring by parents and not by grandparents; he believes that Jane was unfaithful and
that the child is not his. If you were a genetic counselor, what would you tell Allen?
107)
This is a first pregnancy for a 22–year–old woman. She is in her 16th week of pregnancy. She is scheduled for an
amniocentesis and expresses concern that the “baby will be stuck with the needle.” What should the nurse say to
the woman?
108)
A family has four offspring belonging respectively to ABO blood groups A, B, O, and AB. Give the genotypes
and phenotypes of the parents.
109)
A patient is heterozygous for sickle–cell anemia. Explain why the patient would have few or no symptoms of
sickle–cell anemia.
110)
Assume that the allele controlling brown eyes (B) is dominant over that controlling blue eyes (b) in human
beings. (In actuality, eye color in humans is an example of polygene inheritance, which is much more complex
than this.) A blue–eyed man marries a brown–eyed woman, and they have six children, all brown–eyed. What
is the most likely genotype of the father? What is the most likely genotype of the mother? If a seventh child had
blue eyes, what can you conclude about the parents’ genotypes?
111)
The folk singer, Woody Guthrie, died of Huntington’s chorea. One of his parents also died of this disease
affecting the nervous system. The disease usually affects carriers between 25 and 45 years of age and is inherited
as a Mendelian autosomal dominant trait. Using Punnett squares, determine the probability that any of the
three Guthrie offspring will have this devastating disease.
112)
Parents are informed after an amniocentesis that the results show a baby who has an extra number 21
chromosome. Should there be concern and what might the problem be?
Answer Key
Testname: C29
Answer Key
Testname: C29
Answer Key
Testname: C29
23
Answer Key
Testname: C29
24