Deck 13: Mendel and the Gene

Question 1

A recessive allele on the X chromosome is responsible for red-green color blindness in humans.A woman with normal vision whose father is color blind marries a color-blind male.What is the probability that this couple's first son will be color blind?

A)25%
B)50%
C)about 66%
D)75%
E)about 33%

Answer 1

B

Question 2

Suppose two AaBbCc individuals are mated.Assuming that the genes are not linked,what fraction of the offspring are expected to be homozygous recessive for the three traits?

A)1/4
B)1/8
C)1/16
D)1/64
E)1/256

Answer 2

D

Question 3

Assuming independent assortment for all gene pairs,what is the probability that the following parents,AABbCc × AaBbCc,will produce an AaBbCc offspring?

A)1/2
B)1/16
C)1/8
D)3/4
E)9/16

Answer 3

C

Question 4

Different ratios occur in crosses with single gene pairs or two gene pairs.What types of ratios are likely to occur in crosses dealing with a single gene pair?

A)9:3:3:1,1:2:1
B)1:1:1:1,1:4:6:4:1
C)3:1,1:1,1:2:1
D)4:1,1:1,1:4:1

Question 5

When Mendel crossed yellow-seeded and green-seeded pea plants,all the offspring were yellow seeded.When he took these F₁ yellow-seeded plants and crossed them to green-seeded plants,what genotypic ratio is expected?

A)1:2:1
B)3:1
C)9:3:3:1
D)1:1
E)1:1:1:1

Question 6

In rabbits,the homozygous CC is normal,Cc results in deformed legs,and cc results in very short legs.The genotype BB produces black fur,Bb brown fur,and bb white fur.If a cross is made between brown rabbits with deformed legs and white rabbits with deformed legs,what percentage of the offspring would be expected to have deformed legs and white fur?

A)25%
B)33%
C)about 66%
D)100%
E)50%

Question 7

Pseudohypertrophic muscular dystrophy is a human disorder that causes gradual deterioration of the muscles.Only boys are affected,and they are always born to phenotypically normal parents.Due to the severity of the disease,the boys die in their teens.Is this disorder likely to be caused by a dominant or recessive allele? Is its inheritance sex-linked or autosomal?

A)dominant,sex-linked
B)recessive,autosomal
C)recessive,sex-linked
D)incomplete dominant,sex-linked

Question 8

A black guinea pig crossed with an albino guinea pig produced 12 black offspring.When the albino was crossed with a second black animal,6 blacks and 6 albinos were obtained.What is the best explanation for this genetic situation?

A)Albino is recessive;black is dominant.
B)Albino is dominant;black is incompletely dominant.
C)Albino and black are codominant.
D)Albino is recessive;black is codominant.

Question 9

A man and woman are both of normal pigmentation,but both have one parent who is albino (without melanin pigmentation).Albinism is an autosomal (not sex-linked)recessive trait.What is the probability that their first female child will have albinism?

A)0
B)1/8
C)1/2
D)1/4
E)1

Question 10

Phenylketonuria is an inherited disease caused by a recessive autosomal allele.If a woman and her husband are both carriers,what is the probability that their first child will be a phenotypically normal girl?

A)1/4
B)1/16
C)1)0
D)3/16
E)3/8

Question 11

Gray seed color in peas is dominant to white.Assume that Mendel conducted a series of experiments where plants with gray seeds were crossed among themselves,and the following progeny were produced:
302 gray and 98 white.(a)What is the most probable genotype of each parent? (b)Based on your answer in (a)above,what genotypic and phenotypic ratios are expected in these progeny? (Assume the following symbols:
G = gray and g = white. )

A)(a)GG × gg;(b)genotypic = 3:1,phenotypic = 1:2:1
B)(a)Gg × Gg;(b)genotypic = 1:2:1,phenotypic = 3:1
C)(a)GG × Gg;(b)genotypic = 1:2:1,phenotypic = 2:1
D)(a)gg × Gg;(b)genotypic = 1:2,phenotypic = 3:1
E)(a)Gg × Gg;(b)genotypic = 3:1,phenotypic = 9:3:3:1

Question 12

A man and woman are both of normal pigmentation and have a one child out of three who is albino (without melanin pigmentation).Albinism is an autosomal (not sex-linked)recessive trait.What are the genotypes of the albino's parents?

A)One parent must be homozygous for the recessive allele;the other parent can be homozygous dominant,homozygous recessive,or heterozygous.
B)One parent must be heterozygous;the other parent can be homozygous dominant,homozygous recessive,or heterozygous.
C)Both parents must be heterozygous.
D)One parent must be homozygous dominant;the other parent must be heterozygous.
E)Both parents must be homozygous dominant.

Question 13

A heterozygous,but phenotypically wild-type fruit fly (gray body color and normal wings)was mated to a black fly with vestigial wings.The offspring had the following phenotypic distribution:
Wild type,720;black-vestigial,780;black-normal,280;gray-vestigial,220.What conclusion is likely from these results?

A)The black and vestigial loci assort independently from each other.
B)The black and vestigial loci are allelic.
C)Epistasis has modified a 9:3:3:1 ratio.
D)The black and vestigial loci are linked.

Question 14

In Drosophila melanogaster,vestigial (short)wings (vg)are caused by a recessive allele of a gene that independently assorts with a gene pair that influences body hair.Hairy (h)results in a hairy body.A cross is made between a fly with normal (wild)wings and a hairy body and a fly with vestigial wings and a normal (wild)body.The phenotypically normal F₁ flies were crossed among each other,and 1024 F₂ flies were reared.What phenotypes would you expect in the F₂,and in what actual numbers (not ratios)would you expect to find them?

A)phenotypes all wild;numbers expected wild (1024)
B)phenotypes hairy,vestigial hairy;numbers expected hairy (512),vestigial hairy (512)
C)phenotypes wild,vestigial,hairy,vestigial hairy;numbers expected wild (256),vestigial (256),hairy (256),vestigial hairy (256)
D)phenotypes wild,vestigial;numbers expected wild (576),vestigial (576)
E)phenotypes wild,vestigial,hairy,vestigial hairy;numbers expected wild (576),vestigial (192),hairy (192),vestigial hairy (64)

Question 15

A man and woman are both of normal pigmentation,but both have one parent who is albino (without melanin pigmentation).Albinism is an autosomal (not sex-linked)recessive trait.What is the probability that their first child will be an albino?

A)0
B)1/8
C)1/2
D)1/4
E)1

Question 16

Hemophilia is caused by several genetic factors;one,a recessive allele of an X-linked gene,is the subject of this problem.Assume that a man with hemophilia marries a normal woman whose father had hemophilia.What is the probability that they will have a daughter with hemophilia?

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

Question 17

A man has extra digits (six fingers on each hand and six toes on each foot).His wife and their daughter have a normal number of digits.Having extra digits is a dominant trait.The couple's second child has extra digits.What is the probability that their next (third)child will have extra digits?

A)1/2
B)1/16
C)1/8
D)3/4
E)9/16

Question 18

Mendel crossed yellow-seeded and green-seeded pea plants and then allowed the offspring to self-pollinate to produce an F₂ generation.The results were as follows:
6022 yellow and 2001 green (8023 total).The allele for green seeds has what relationship to the allele for yellow seeds?

A)dominant
B)incomplete dominant
C)recessive
D)codominant

Question 19

In tigers,a recessive allele causes a white tiger (absence of fur pigmentation).If one phenotypically normal tiger that is heterozygous is mated to another that is phenotypically white,what percentage of their offspring is expected to be white?

A)50%
B)75%
C)0%
D)100%
E)25%

Question 20

In birds,sex is determined by a ZW chromosome scheme that is much like the typical XY scheme seen in humans and many other organisms,except that the system is reversed:
Males are ZZ (similar to XX in humans)and females are ZW (similar to XY in humans).A lethal recessive allele that causes death of the embryo occurs on the Z chromosome in pigeons.What would be the sex ratio in the offspring of a cross between a male heterozygous for the lethal allele and a normal female?

A)1:1 male to female
B)4:1 male to female
C)3:1 male to female
D)1:2 male to female
E)2:1 male to female

Question 21

Glucose-6-phosphate dehydrogenase deficiency (G6PD)is inherited as a recessive allele of an X-linked gene in humans.A woman whose father suffered from G6PD marries a normal man.(a)What proportion of their sons is expected to be G6PD? (b)If the husband was not normal but was G6PD deficient,would you change your answer in part (a)?

A)(a)100%;(b)no
B)(a)1/2;(b)yes
C)(a)2/3;(b)no
D)(a)1/2;(b)no
E)(a)zero;(b)no

Question 22

Whenever the dominant allele of either (or both)gene A or gene B is present,red color is produced.A cross of AaBb × AaBb can be expected to yield how many red offspring out of 16? Assume the genes are not linked.

A)1
B)4
C)12
D)15
E)16

Question 23

Figure 13.1
In a Drosophila experiment,a cross was made between homozygous wild-type females and yellow-bodied males.All of the resulting F₁s were phenotypically wild type.However,adult flies of the F₂ generation (resulting from matings of the F₁s)had the characteristics shown in the figure above:
(a)Is the mutant allele for yellow body recessive or dominant?
(b)Is the yellow locus autosomal (not X-linked)or X-linked?

A)(a)recessive;(b)X-linked
B)(a)recessive;(b)not X-linked
C)(a)dominant;(b)X-linked
D)(a)dominant;(b)not X-linked

Question 24

Snapdragons are flowers that come in a variety of colors,including red,pink,and white.A series of crosses with snapdragons having flowers of different colors produced the following results:
Pink × pink:
27 pink,13 red,14 white
Red × red:
All red
White × white:
All white
Pink × white:
29 pink,26 white
Pink × red:
28 pink,27 red
White × red:
All pink
Based on the results,what is the most reasonable explanation for the inheritance of these flower colors?

A)more than two alleles
B)incomplete dominance
C)codominance
D)pleiotropic effects
E)qualitative effects

Question 25

Hemophilia is caused by several genetic factors;one,a recessive allele of an X-linked gene,is the subject of this problem.Assume that a man with hemophilia marries a normal woman whose father had hemophilia.What is the probability that their first son will have hemophilia?

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

Question 26

In Drosophila melanogaster,vestigial wings are caused by a recessive allele of a gene that is linked to a gene with a recessive allele that causes black body color.Morgan crossed black-bodied normal-winged females and gray-bodied vestigial-winged males.The F₁ were all gray bodied,normal winged.After examining the F₂ progeny,Morgan calculated the map distance to be 17 map units.Which of the following is correct about the F₂ progeny?

A)black-bodied normal-winged flies = 17%
B)black-bodied,normal-winged flies PLUS gray-bodied,vestigial-winged flies = 17%
C)gray-bodied,normal-winged flies PLUS black-bodied,vestigial-winged flies = 17%
D)black-bodied,vestigial-winged flies = 17%

Question 27

Regarding an allelic pair for flower color in snapdragons,heterozygotes have pink flowers,whereas the two homozygotes have red flowers or white flowers.When plants with red flowers are crossed with plants with white flowers,what proportion of the offspring is expected to have pink flowers?

A)50%
B)0%
C)100%
D)25%
E)75%

Question 28

In humans,ABO blood types refer to glyocproteins in the membranes of red blood cells.There are three alleles for this autosomal gene:
IA,IB,and i.The IA allele codes for the A glycoprotein,The IB allele codes for the B glycoprotein,and the i allele doesn't code for any membrane glycoprotein.IA and IB are codominant,and i is recessive to both IA and IB.People with A type blood have the genotypes IAIA or IAi,people with type B blood are IBIB or IBi,people with type AB blood are IAIB,and people with O type blood are ii.If a woman with type AB blood marries a man with type O blood,which of the following blood types could their children possibly have?

A)A and B
B)AB and O
C)A,B,and O
D)A,B,and AB
E)A,B,AB,and O

Question 29

A homozygous tomato plant with red fruit and yellow flowers was crossed with a homozygous tomato plant with golden fruit and white flowers.The F₁ all had red fruit and yellow flowers.The following phenotypes were obtained in the F₂:
Red fruit and yellow flowers-41
Red fruit and white flowers-7
Golden fruit and yellow flowers-8
Golden fruit and white flowers-44
How many map units separate these genes?

A)17.6
B)15
C)17.1
D)18.1
E)35

Question 30

A man who carries an allele of an X-linked gene will pass it on to _____.

A)all of his daughters
B)half of his daughters
C)all of his sons
D)half of his sons
E)all of his children

Question 31

In humans,blue eyes are inherited as a recessive autosomal trait and color blindness is an X-linked recessive trait.A woman with blue eyes and normal color vision whose father was color blind marries a man who also has normal color vision.He has brown eyes but his mother had blue eyes.Which of the following do you expect to be true for their daughters?

A)One-half of their daughters will have normal color vision and brown eyes;1/2 of their daughters will have normal color vision and blue eyes.
B)Their daughters will all have normal color vision and brown eyes.
C)One-fourth of their daughters will be color blind and have blue eyes,1/4 of their daughters will be color blind and have brown eyes,1/4 of their daughters will have normal color vision and blue eyes,1/4 of their daughters will have normal color vision and brown eyes.
D)Their daughters will all have normal color vision and have blue eyes.
E)One-half of their daughters will be color blind and have blue eyes;1/2 their daughters will be color blind and have brown eyes.

Question 32

In humans,blue eyes are inherited as a recessive autosomal trait and color blindness is an X-linked recessive trait.A woman with blue eyes and normal color vision whose father was color blind marries a man who also has normal color vision.He has brown eyes,but his mother had blue eyes.Which of the following do you expect to be true for their sons?

A)One-half of their sons will have normal color vision and brown eyes;1/2 of their sons will have normal color vision and blue eyes.
B)Their sons will all have normal color vision and brown eyes.
C)One-fourth of their sons will be color blind and have blue eyes,1/4 of their sons will be color blind and have brown eyes,1/4 of their sons will have normal color vision and blue eyes,1/4 of their sons will have normal color vision and brown eyes.
D)Their sons will all have normal color vision and blue eyes.
E)One-half of their sons will be color blind and have blue eyes;1/2 their sons will be color blind and have brown eyes.