Deck 3: Mendelian Genetics

Question 1

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

Answer 1

B

Question 2

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?

Answer 2

1/4 X 1/2 = 1/8

Question 3

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

Answer 3

meiosis I,when homologous chromosomes go to opposite poles

Question 4

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

Question 5

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?

Question 6

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

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

Question 7

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

Question 8

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 9

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 10

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 11

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

Question 12

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

Question 13

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 14

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.
CrossProgeny
solidstriped
(a)solid X striped5560
(b)solid X solid360
(c)striped X striped065
(d)solid X solid9230
(e)solid X striped440
Define gene symbols and give the possible genotypes of the parents of each cross.

Question 15

Assume that a black guinea pig crossed with an albino guinea pig produced 5 black offspring.When the albino was crossed with a second black guinea pig,4 black and 3 albino offspring were produced.What genetic explanation would apply to these data?

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

Question 16

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 17

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 18

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

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

Question 19

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

Question 20

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

Question 21

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 F? 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 22

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 23

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

Question 24

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

Question 25

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 26

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 27

Provide simple definitions that distinguish segregation and independent assortment.

Question 28

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

Question 29

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 30

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

Question 31

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 32

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 33

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 34

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

Question 35

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 36

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

Question 37

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

Question 38

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

Question 39

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

Question 40

What are two typical testcross ratios?

Question 41

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

Question 42

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

Question 43

A 1:1 phenotypic ratio is expected from a monohybrid testcross with complete dominance.

Question 44

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 45

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 46

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 47

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

Question 48

In what ways is sample size related to statistical testing?

Question 49

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 50

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

Question 51

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

Question 52

Mendel's Law of Segregation is supported by a 1:1 testcross ratio.

Question 53

In a Chi-square test,as the value of the ?² increases,the likelihood of rejecting the null hypothesis ________.

Question 54

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

Question 55

A gene can have a maximum of two alleles.

Question 56

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

Question 57

A 9:3:3:1 phenotypic ratio is expected from a dihybrid testcross.

Question 58

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?