Deck 3: Mendelian Genetics

Question 1

Which types of phenotypic ratios are likely to occur in crosses when dealing with a single gene pair for which all the genotypic combinations are of equal viability?

A) 9:3:3:1, 27:9:9:9:3:3:3:1
B) 12:3:1, 9:7
C) 1:2:1, 3:1
D) 2:3, 1:2
E) 1:4:6:4:1, 1:1:1:1

Answer 1

C

Question 2

Assuming no crossing over between the gene in question and the centromere, when do alleles segregate during meiosis?

Answer 2

meiosis I, when homologous chromosomes go to opposite poles

Question 3

Albinism, lack of pigmentation in humans, results from an autosomal recessive gene
(a). Two parents with normal pigmentation have an albino child.
a() What is the probability that their next child will be albino?
b() What is the probability that their next child will be an albino girl?
c() What is the probability that their next three children will be albino?

Answer 3

(a) 1/4
(b) 1/4 × 1/2 = 1/8
(c) 1/4 × 1/4 × 1/4 = 1/64

Question 4

Tightly curled or wooly hair is caused by a dominant gene in humans. If a heterozygous curly -haired person marries a person with straight hair, what percentage of their offspring would be expected to have straight hair?

A) 75% straight
B) 100% straight
C) 50% straight
D) 25% straight
E) It is impossible to predict the outcome.

Question 5

Name the single individual whose work in the mid -1800s contributed to our understanding of the particulate nature of inheritance as well as the basic genetic transmission patterns. With which organism did this person work?

A) George Beadle; Neurospora
B) Thomas Hunt Morgan; Drosophila
C) Charles Darwin; Ephestia
D) Calvin Bridges; Drosophila
E) Gregor Mendel; Pisum sativum

Question 6

Dentinogenesis imperfecta is a rare, autosomal, dominantly inherited disease of the teeth that occurs in about one in 8000 people (Witkop, 1957). The teeth are somewhat brown in color, and the crowns wear down rapidly. Assume that a male with dentinogenesis
imperfecta and no family history of the disease marries a woman with normal teeth.
What is the probability that
a() their first child will have dentinogenesis imperfecta?
b() their first two children will have dentinogenesis imperfecta?
c() their first child will be a girl with dentinogenesis imperfecta?

Question 7

Polydactyly is expressed when an individual has extra fingers and/or toes. Assume that a man with six fingers on each hand and six toes on each foot marries a woman with a normal number of digits. Having extra digits is caused by a dominant allele. The couple has a son with normal hands and feet, but the couple's second child has extra digits. What is the probability that their next child will have polydactyly?

A) 3/4
B) 1/32
C) 7/16
D) 1/2
E) 1/8

Question 8

Assume that you have a garden and some pea plants have solid leaves and others have striped leaves. You conduct a series of crosses [(a) through (e)] and obtain the results
given in the table.
Define gene symbols and give the possible genotypes of the parents of each cross.

Question 9

The fundamental Mendelian process that involves the separation of contrasting genetic elements at the same locus is called _.

A) continuous variation
B) independent assortment
C) dominance or recessiveness
D) discontinuous variation
E) segregation

Question 10

Albinism, lack of pigmentation in humans, results from an autosomal recessive gene
(a). Two parents with normal pigmentation have an albino child. What is the probability that their next child will be an albino girl?

Question 11

In peas, gray seed color is dominant to white. For the purposes of this question, assume that Mendel crossed plants with gray seeds with each other and the following progeny were produced: 320 gray and 80 white.
a() What is the most probable genotype of each parent?
b() What genotypic and phenotypic ratios are expected in the progeny of such a cross?

Question 12

The Chi -square test involves a statistical comparison between measured (observed) and predicted (expected) values. One generally determines degrees of freedom as _.

A) one less than the number of classes being compared
B) one more than the number of classes being compared
C) ten minus the sum of the two categories
D) the number of categories being compared
E) the sum of the two categories

Question 13

Assume that a black guinea pig crossed with an albino guinea pig produced five black offspring. When the albino was crossed with a second black guinea pig, four black and three albino offspring were produced. What genetic explanation would apply to these data?

A) albino = recessive; black = dominant
B) albino and black = codominant
C) albino = dominant; black = incompletely dominant
D) albino = recessive; black = recessive
E) None of the answers listed are correct.

Question 14

A recessive allele in tigers causes the white tiger. If two normally pigmented tigers are mated and produce a white offspring, what percentage of their remaining offspring would be expected to have normal pigmentation?

A) 25%
B) 50%
C) about 66%
D) 75%
E) about 90%

Question 15

A certain type of congenital deafness in humans is caused by a rare autosomal (not X -linked) dominant gene.
a() In a mating involving a deaf man and a deaf woman (both heterozygous), would you expect all the children to be deaf? Explain your answer.
b() In a mating involving a deaf man and a deaf woman (both heterozygous), could all the children have normal hearing? Explain your answer.
c() Another form of deafness is caused by a rare autosomal recessive gene. In a mating involving a deaf man and a deaf woman, could some of the children have normal
hearing? Explain your answer.

Question 16

Which of the following groups of scientists were influential around the year 1900 in setting the stage for our present understanding of transmission genetics?

A) Hippocrates, Aristotle, Kolreuter
B) Watson, Crick, Wilkins, Franklin
C) Darwin, Mendel, Lamarck
D) Beadle, Tatum, Lederberg
E) deVries, Correns, Tschermak, Sutton, Boveri

Question 17

Assume that in a series of experiments, plants with round seeds were crossed with
plants with wrinkled seeds and the following offspring were obtained: 220 round and 180 wrinkled.
a() What is the most probable genotype of each parent?
b() What genotypic and phenotypic ratios are expected?
c() Based on the information provided in part (b), what are the expected (theoretical) numbers of progeny (400 total) of each phenotypic class?

Question 18

According to Mendel's model, because of ________, all possible combinations of gametes will be formed in equal frequency.

Question 19

Assuming a typical monohybrid cross in which one allele is completely dominant to the other, what ratio is expected if the F1s are crossed?

Question 20

Albinism, lack of pigmentation in humans, results from an autosomal recessive gene
(a). Two parents with normal pigmentation have an albino child. What is the probability that their next child will be albino?

Question 21

How many kinds of gametes will be expected from an individual with the genotype
PpCcTTRr?

Question 22

Under what conditions does one expect a 1:1:1:1 ratio?

Question 23

Under what conditions does one expect a 9:3:3:1 ratio?

Question 24

Tightly curled hair is caused by a dominant autosomal gene in humans. If a heterozygous curly -haired person marries a person with straight hair, what phenotypes (and in what proportions) are expected in the offspring?

Question 25

Albinism, lack of pigmentation in humans, results from an autosomal recessive gene
(a). Two parents with normal pigmentation have an albino child. What is the probability that their next three children will be albino?

Question 26

The autosomal (not X -linked) gene for brachydactyly, short fingers, is dominant to normal finger length. Assume that a female with brachydactyly in the heterozygous condition is married to a man with normal fingers. What is the probability that
a() their first child will have brachydactyly?
b() their first two children will have brachydactyly?
c() their first child will be a brachydactylous girl?

Question 27

Which phenotypic ratio is likely to occur in crosses of two completely dominant, independently segregating gene pairs when both parents are fully heterozygous?

Question 28

A certain type of congenital deafness in humans is caused by a rare autosomal
recessive gene. In a mating involving a deaf man and a deaf woman, could some of the children have normal hearing? Explain your answer.

Question 29

What conditions are likely to apply if the progeny from the cross AaBb × AaBb appear in the 9:3:3:1 ratio?

Question 30

Provide simple definitions that distinguish segregation and independent assortment.

Question 31

The phenotype of vestigial (short) wings (vg) in Drosophila melanogaster is caused by a recessive mutant gene that independently assorts with a recessive gene for hairy (h)
body. Assume that a cross is made between a fly with normal wings and a hairy body and a fly with vestigial wings and normal body hair. The wild -type F1 flies were
crossed among each other to produce 1024 offspring. Which phenotypes would you
expect among the 1024 offspring, and how many of each phenotype would you expect?

Question 32

How many different types of gametes can be produced by an individual with the genotype AABbCCddEeFf?

Question 33

A certain type of congenital deafness in humans is caused by a rare autosomal dominant gene. In a mating involving a deaf man and a deaf woman (both
heterozygous), would you expect all the children to be deaf? Explain your answer.

Question 34

What is the probability of flipping a penny and a nickel and obtaining one head and one tail?

Question 35

Two organisms, AABBCCDDEE and aabbccddee, are mated to produce an F1 that is
self -fertilized. If the capital letters represent dominant, independently assorting alleles:
a() How many different genotypes will occur in the F2?
b() What proportion of the F2 genotypes will be recessive for all five loci?
c() Would you change your answers to part (a) and/or part (b) if the initial cross occurred between AAbbCCddee × aaBBccDDEE parents?
d() Would you change your answers to part (a) and/or part (b) if the initial cross occurred between AABBCCDDEE × aabbccddEE parents?

Question 36

For the purposes of this question, assume that being Rh+ is a consequence of D and that Rh - individuals are dd. The ability to taste phenylthiocarbamide (PTC) is
determined by the gene symbolized T (tt are nontasters). A female whose mother was Rh - has the MN blood group, is Rh+, and a nontaster of PTC, and is married to a man who is MM, Rh -, and a nontaster. List the possible genotypes of their children. Assume that all the loci discussed in this problem are autosomal and independently assorting.

Question 37

Assuming independent assortment, what proportion of the offspring of the cross
AaBbCcDd × AabbCCdd will have the aabbccdd genotype?

Question 38

Among dogs, short hair is dominant to long hair and dark coat color is dominant to white (albino) coat color. Assume that these two coat traits are caused by
independently segregating gene pairs. For each of the crosses given below, write the most probable genotype (or genotypes if more than one answer is possible) for the
parents. It is important that you select a realistic symbol set and define each symbol below.
Assume that for cross (d), you were interested in determining whether fur color
follows a 3:1 ratio. Set up (but do not complete the calculations) a Chi -square test for these data [fur color in cross (d)].

Question 39

A certain type of congenital deafness in humans is caused by a rare autosomal
dominant gene. In a mating involving a deaf man and a deaf woman, could all the children have normal hearing? Explain your answer.

Question 40

What are two typical ratios that result from crossing heterozygotes with homozygous organisms?

Question 41

Assuming complete dominance, a 3:1 phenotypic ratio is expected from a monohybrid sib or self -cross.

Question 42

Assume that a Chi -square test provided a probability value of 0.02. Should the null hypothesis be accepted?

Question 43

A gene can have a maximum of two alleles.

Question 44

Assume that a Chi -square test was conducted to test the goodness of fit to a 9:3:3:1 ratio and a Chi -square value of 10.62 was obtained. Should the null hypothesis be accepted?

Question 45

Mendel's Law of Segregation is supported by a 1:1 ratio of offspring when one parent is heterozygous and the other is homozygous recessive.

Question 46

Assume that a Chi -square test was conducted to test the goodness of fit to a 3:1 ratio and that a Chi -square value of 2.62 was obtained. Should the null hypothesis be
accepted? How many degrees of freedom would be associated with this test of significance?

Question 47

In a Chi -square test, as the value of the ç2 increases, the likelihood of rejecting the null hypothesis _.

Question 48

Assume that a cross is made between a heterozygous tall pea plant and a homozygous short pea plant. Fifty offspring are produced in the following frequency:
30 = tall
20 = short
a() What frequency of tall and short plants is expected?
b() To test the goodness of fit between the observed and expected values, provide the needed statement of the null hypothesis.
c() Compute a Chi -square value associated with the appropriate test of significance.
d() How many degrees of freedom are associated with this test of significance?

Question 49

In a Chi -square analysis, what condition causes one to reject (fail to accept) the null hypothesis?

Question 50

The nonfunctional form of a gene is called a wild -type allele.

Question 51

Mendel's discoveries were well received and understood by his contemporaries.

Question 52

If one is testing a goodness of fit to a 9:3:3:1 ratio, how many degrees of freedom would be associated with the Chi -square analysis?

Question 53

To test Mendel's Law of Segregation, the experimenter needs a minimum of two contrasting forms of a gene.

Question 54

In studies of human genetics, usually a single individual brings the condition to the attention of a scientist or physician. When pedigrees are developed to illustrate
transmission of the trait, what term is used to refer to this individual?

Question 55

A 1:1 phenotypic ratio is expected from a monohybrid cross involving a heterozygote with a homozygous recessive organism.

Question 56

In what ways is sample size related to statistical testing?

Question 57

Mendel's postulate of independent assortment is supported by a 1:1:1:1 testcross ratio.

Question 58

A 9:3:3:1 phenotypic ratio is expected from a dihybrid cross between a double heterozygote and a fully recessive organism.