Question 1

Roberts Syndrome is an extremely rare genetic disorder that is characterized by mild to severe prenatal retardation or disruption of cell division,leading to malformation of the bones in the skull,face,arms,and legs.Shown below is a pedigree for a family with Robert's Syndrome.Based on this pedigree what mode of inheritance does Roberts Syndrome exhibit? 
A)autosomal dominant
B)autosomal recessive
C)sex-linked dominant
D)sex-linked recessive
E)random

Accepted Answer

Roberts Syndrome appears to be inherited in an autosomal recessive manner as both parents are carriers of the trait and two of their children have the disorder.

Question 2

Huntington disease is a neurodegenerative genetic disorder that typically manifests itself around age 40.A 25-year-old woman comes to your genetic counseling center because she knows that Huntington disease occurs in members of her father's family.Her paternal grandfather was afflicted,but so far her 50-year-old father shows no symptoms.Her two great-great grandmothers on her father's side were healthy well into their 90s,but one of her great-great grandfathers died of unknown causes at 45.Testing for Huntington disease is extremely expensive,but she is concerned that she may fall victim to this disease and wants to plan her life accordingly.After examining her pedigree you advise her to
A)get tested because there is no possibility that she is homozygous.
B)not get tested because only males in her family get the disease.
C)get tested because her father could be a carrier.
D)not get tested because her father is only a carrier and it is very unlikely her mother is a carrier.
E)not get tested because her 50-year-old father shows no symptoms.

Accepted Answer

Huntington's disease is an autosomal dominant disorder, meaning that only one copy of the defective gene, inherited from either parent, is sufficient to cause the disease. The woman's concern is valid because her father, despite not showing symptoms, could still be a carrier of the gene mutation. Since the disease can manifest later in life, the fact that her father is currently asymptomatic does not eliminate the possibility of him being a carrier. Therefore, she could have inherited the gene and might develop the disease later.

Question 3

What data would you expect to see regarding the distribution of phenotypes from a cross of purple pea plants that are heterozygous for flower color and plant height? (Purple is dominant to white;dwarf is dominant to tall. )
A)63 purple dwarf;25 purple tall;19 white dwarf;7 white tall
B)132 purple dwarf;138 white tall
C)54 purple dwarf;6 white tall
D)100% purple dwarf
E)27 purple dwarf;28 purple tall;31 white dwarf;29 white tall

Accepted Answer

The cross of heterozygous purple dwarf pea plants (PpDd x PpDd) would follow a dihybrid cross pattern, resulting in a phenotypic ratio of 9:3:3:1 for the traits in question. This translates to 9 parts purple dwarf, 3 parts purple tall, 3 parts white dwarf, and 1 part white tall, which matches the distribution given in option A when considering a total of 114 offspring (63 purple dwarf, 25 purple tall, 19 white dwarf, 7 white tall).

Question 4

What features of meiosis allow for independent assortment of chromosomes?
A)Random alignment of homologous chromosomes on the metaphase plate
B)Separation of sister chromatids
C)Reduction of chromosome number from diploid to haploid
D)Both the separation of sister chromatids and the reduction of chromosome number from diploid to haploid

Accepted Answer

The random alignment of homologous chromosomes on the metaphase plate during meiosis I allows for independent assortment of chromosomes. This means that the chromosomes can line up in any combination, leading to genetic diversity in the resulting gametes.

Answer: D 
 Both the separation of sister chromatids and the reduction of chromosome number from diploid to haploid occur during meiosis. These processes also contribute to independent assortment of chromosomes, as they result in the separation and mixing of genetic material between homologous chromosomes.

Question 5

In wolves,gray coat color (G)is dominant to black (g)and brown eyes (B)are dominant to blue (b).The genes that control these traits are located on different chromosomes.The alpha male of the pack has the dominant phenotype for both traits and is heterozygous for both traits.The alpha female has brown eyes and a black coat;she is heterozygous for eye color.The alpha male and the alpha female mate.What proportion of their offspring will have the same phenotype as the mother?
A)1/16
B)3/16
C)3/8
D)1/2
E)None

Accepted Answer

The alpha male's genotype is GgBb, and the alpha female's genotype is ggBb. The offspring with the same phenotype as the mother (black coat and brown eyes) will have the genotype ggB_. The probability of gg is 1/2, and the probability of B_ is 3/4. Therefore, the proportion is (1/2) * (3/4) = 3/8.

Question 6

Color blindness is a recessive X-linked trait.A normal couple has a color-blind child.Who else in this family is probably color blind?
A)the child's maternal grandfather
B)the child's maternal grandmother
C)the child's paternal grandfather
D)the child's paternal grandmother
E)the child's maternal grandmother or grandfather

Accepted Answer

Since color blindness is a recessive X-linked trait, a color-blind child must have inherited the recessive allele from their mother, who must have been a carrier if she is not color-blind herself. The mother, in turn, must have inherited the recessive allele from her father, making the child's maternal grandfather the most likely to be color-blind.

Question 7

In Hodags (mythical creatures of Wisconsin),brown fur (B)is dominant over gray fur (b)and long horns (H)are dominant over short horns (h).Two true-breeding hodags,one with brown fur and long horns and the other with gray fur and short horns mate and produce an F₁.Two F₁ individuals are mated.What proportion of the offspring will exhibit a phenotypic combination that is different from the P generation? Assume the genes for fur color and horn length are on different chromosomes. A)1/2 B)9/16 C)3/16 D)6/16 E)1/16

Accepted Answer

The answer of In Hodags (mythical creatures of Wisconsin),brown fur...

Question 8

In mammals,males are ________ and females are _______ for their sex chromosomes.
A)heterozygous,homozygous
B)hemizygous,homozygous
C)homozygous,heterozygous
D)hemizygous,heterozygous
E)heterozygous,hemizygous

Accepted Answer

Males have one X and one Y chromosome (XY), making them heterozygous for their sex chromosomes, while females have two X chromosomes (XX), making them homozygous.

Question 9

Hemophilia A is an X-linked recessive genetic condition.In humans it is due to a mutation in the F8 gene,which encodes a protein called coagulation factor VII.Coagulation factors are proteins important in blood clotting.Individuals with hemophilia,when injured,bleed longer than a normal,healthy individual;the inability to normally clot blood can be life threatening.Which of the following statements is NOT a reason why hemophilia is much more common in males than in females?
A)A female with one defective allele makes enough normal coagulation factor VII to clot blood and will not have hemophilia A
B)Males are hemizygous for the F8 gene,so they will have hemophilia A if they have one defective allele
C)Females have to receive a defective allele from both their mother and their father to get hemophilia A
D)Males have to receive a defective allele only from their father to get hemophilia A

Accepted Answer

Males inherit the X chromosome from their mother and the Y chromosome from their father. Therefore, a male cannot inherit an X-linked allele from his father, making statement D incorrect.

Question 10

A homologous pair of chromosomes at the beginning of mitosis will possess _______ alleles for each locus.
A)2
B)4
C)8
D)1
E)50% of the

Accepted Answer

The answer of A homologous pair of chromosomes at the...

Question 11

An X-linked gene is
A)a gene that encodes traits seen only in females.
B)a gene on the X chromosome.
C)a gene found on any chromosome;they are X-shaped when they are metaphase chromosomes.
D)a gene that is turned on (makes protein)only when the female hormone estrogen is present.
E)a gene on the X chromosome that encodes traits seen only in females.

Accepted Answer

An X-linked gene is a gene that is located on the X chromosome. This means that males, who only have one X chromosome, will express the trait if they inherit the X-linked gene from their mother. Females, who have two X chromosomes, will express the trait if they inherit the X-linked gene from both parents.

Question 12

Nearsightedness is dominant to normal vision and hazel eyes are dominant to blue eyes.A nearsighted woman with hazel eyes who is heterozygous for both traits marries a man with normal vision and hazel eyes.His genotype for eye color is the same as his wife's.Their three children all have blue eyes and normal vision.What is the probability that their next child will have blue eyes and be nearsighted?
A)1/4
B)1/2
C)3/8
D)1/8
E)5/8

Accepted Answer

The woman is heterozygous for both nearsightedness and hazel eyes, so her genotype can be represented as NnHh. The man is normal and heterozygous for eye color, so his genotype can be represented as nnHh.

To determine the probability of their next child having blue eyes and being nearsighted, we need to use Punnett squares.

* N = nearsightedness allele, n = normal vision allele
* H = hazel eyes allele, h = blue eyes allele

|   | Nn    | nH   | Nh    | nh   |
|---|-------|------|-------|------|
| Hh | NHhHh | nHhHh| NhHhHh| nhHhHh|
| hH | NnHh  | nnHh | NhnHh | nnHh |
| hh | Nnhh  | nnhh | Nhnh  | nhhh |

The four boxes highlighted in bold show the possible offspring that have blue eyes and are nearsighted. There are a total of 16 possible offspring, and 2 of them fit the criteria, so the probability is 2/16 or 1/8.

Therefore, the answer is D) 1/8.

Question 13

An organism has one Z chromosome and one W chromosome.That organism is
A)a female bird.
B)a male bird.
C)a female insect.
D)a male insect.
E)a male or female human.

Accepted Answer

In birds, the sex chromosomes are Z and W. Females have one Z and one W chromosome (ZW), while males have two Z chromosomes (ZZ).

Question 14

Roberts Syndrome is an extremely rare genetic disorder that is characterized by mild to severe prenatal retardation or disruption of cell division,leading to malformation of the bones in the skull,face,arms,and legs.Shown below is a pedigree for a family with Robert's Syndrome.What is the genotype of individual II-C? (R = wild type;r = Robert's syndrome) 
A)RR
B)rr
C)Rr
D)R
E)r

Accepted Answer

Individual II-C has Robert's Syndrome, which is a recessive disorder. Therefore, this individual must have two copies of the recessive allele, which is "r." The only genotype that satisfies this condition is Rr. Therefore, the correct answer is C) Rr.

Question 15

For mechanisms of sex determination,which of the following is incorrectly paired?
A)X-Y,cow
B)X-O,grasshopper
C)ZZ-ZW,bluebird
D)1n-2n,pea plant
E)high temperature-low temperature,alligator

Accepted Answer

1n-2n is not a mechanism of sex determination. It refers to the ploidy level (number of sets of chromosomes) in gametes and zygotes of the pea plant.

Question 16

Incomplete dominance is when
A)the phenotypes of a heterozygote and a homozygous dominant are indistinguishable.
B)the phenotype of a heterozygote is not the same as either parent,but it is somewhere between the two parents.
C)the phenotype of a heterozygote clearly exhibits the phenotypes of both parents (it is not an intermediate).
D)an allele is dominant at some times and recessive at others.
E)the phenotypic expression at one locus alters the gene at a second locus.

Accepted Answer

In incomplete dominance, the phenotype of the heterozygote is a blend of the two homozygous phenotypes, resulting in an intermediate phenotype. It is not completely dominant or recessive.

Question 17

In wolves,gray coat color (G)is dominant to black (g)and brown eyes (B)are dominant to blue (b).The genes that control these traits are located on different chromosomes.The alpha male of the pack has the dominant phenotype for both traits and is heterozygous for both traits.The alpha female has brown eyes and a black coat;she is heterozygous for eye color.Which option represents gametes that would be made by the alpha female?
A)B,b,and g
B)Bg and bg
C)Bb and gg
D)BG,Bg,bG,bg
E)None of these

Accepted Answer

The alpha female has brown eyes and a black coat, with heterozygosity for eye color (Bb) but homozygosity for coat color (gg), so she can only produce gametes with combinations of these alleles, which are Bg and bg.

Question 18

An organism that is heterozygous for two traits can produce a maximum of _______ different gametes for these traits.
A)2
B)4
C)2;if they are on the same chromosome
D)27
E)8

Accepted Answer

When an organism is heterozygous for two traits, it means that it carries two different alleles for each trait. This can be represented as AaBb. During meiosis, the alleles on homologous chromosomes can undergo independent assortment, meaning that they can segregate into different gametes. This leads to the production of four different gamete combinations: AB, Ab, aB, and ab. Therefore, the maximum number of different gametes that an organism that is heterozygous for two traits can produce is four.

Question 19

Human males produce
A)sperm,half contain an X chromosome,half contain a Y chromosome.
B)sperm with neither an X nor a Y;gametes do not contain sex chromosomes.
C)gametes,all contain a Y chromosome.
D)sperm,all contain an X chromosome.
E)gametes,all contain both an X chromosome and a Y chromosomE.

Accepted Answer

Human males produce sperm which are gametes that contain either an X or a Y chromosome. Half of the sperm contain an X chromosome and the other half contain a Y chromosome, which determines the sex of the offspring when the sperm fertilizes an egg. Therefore, choice A is the best choice.

Question 20

Hemophilia is a sex-linked recessive condition that results in deficient blood clotting.The disease causes excessive bleeding which occurs spontaneously or upon slight injury.In dogs (as in humans)hemophilia is caused by a defect in a gene on the X chromosome.What will be the results of mating between a normal,non-carrier female dog and a male dog with hemophilia?
A)All female offspring will be normal and half the male offspring will have hemophiliA.
B)Half the male offspring will be normal and half will have hemophilia;all females will be carriers.
C)All the female offspring will be normal and all male offspring will be carriers.
D)Half the female offspring will have hemophilia and half will be carriers,all male offspring will be normal.
E)All of the offspring will be normal,but all females will be carriers.

Accepted Answer

Since hemophilia is a sex-linked recessive condition and the mother is normal and non-carrier (XX), and the father has hemophilia (XhY), all female offspring (XhX) will be carriers, and all male offspring (XY) will be normal.

Quiz 14: Patterns of Inheritance

What data would you expect to see regarding the distribution of phenotypes from a cross of purple pea plants that are heterozygous for flower color and plant height? (Purple is dominant to white;dwarf is dominant to tall. )

What features of meiosis allow for independent assortment of chromosomes?

Color blindness is a recessive X-linked trait.A normal couple has a color-blind child.Who else in this family is probably color blind?

In mammals,males are __ and females are _ for their sex chromosomes.

A homologous pair of chromosomes at the beginning of mitosis will possess _______ alleles for each locus.

An X-linked gene is

An organism has one Z chromosome and one W chromosome.That organism is

For mechanisms of sex determination,which of the following is incorrectly paired?

Incomplete dominance is when

An organism that is heterozygous for two traits can produce a maximum of _______ different gametes for these traits.

Human males produce