Genetic Counseling

Is the 12th chromosome that you received at conception from your mother the same as your great grandmother's 12th chromosome? Use your knowledge from this chapter to answer this question.

What is the function of a gene?

The mutant strain maroon-like has an X-linked mutant allele (X^m) that results in deep maroon-colored eyes in homozygous females and hemizygous males. To prove to a skeptical friend that this trait is in fact X-linked, you set up a reciprocal cross against the wild type. What are the expected genotypic and phenotypic frequencies of each half of this crossing experiment?

Look at the pedigree below. What is the genotype of the parents of individuals 1, 2, and 3?

A. cannot be determined

B. ff

C. Ff

D. FF

Look at the pedigree. If individual 3 marries a carrier for cystic fibrosis, what would be the chance of cystic fibrosis in their children?

A. 75% carrier, 25% cystic fibrosis

B. 25% normal, 50% carrier, 25% cystic fibrosis

C. 75% cystic fibrosis, 25% carrier

D. 50% carrier, 50% cystic fibrosis

Look at the pedigree below. Let's say that individual 2 has achild with a man who does not have the disease and is not a carrier (FF). What are the results of their cross? Do a Punnet Square.

A. 50% Ff, 50% F?

B. 50% FF, 50% F?

C. 50% FF, 50% Ff

D. We cannot determine this because we don't know the genotype of individual 2.

Individuals III-3 and III-3 are expecting their first child when they became aware that they both havea family history of this recessive condition. As counselor, you can calculate the probability that they are carriers and that their child will be affected with the condition.

What is the probability that III-3 is a carrier (Rr)?

The following pedigree shows _____ type of inheritance.

A. dominant

B. both dominant and recessive

C. not enough information

D. recessive

Based on the pedigree shown below, what is the genotype of II-1?

A. AA

B. aa

C. Aa

D. AA or Aa

E. Aa or aa

F. AA or aa

G. AA or Aa or aa

Based on the pedigree shown below, what is the genotype of IV-3?

A. AA

B. aa

C. Aa

D. AA or Aa

E. Aa or aa

F. AA or aa

G. AA or Aa or aa

The hemophilia disease is caused by an X-linked recessive gene (gene H). The pedigree of a family with history of hemophilia disease is shown below. Which of the following is the genotype of II-1?

A. X^hX^h

B. X^HX^?

C. X^HX^H

D. X^HX^h

E. X^HY

F. X^hY

How many female who have the disease in this pedigree?

A. 1

B. 2

C. 3

D. 4

E. 5

F. 6

G. 7

Which of the following is the clearest indication in a pedigree that a trait is dominant?

A. A father passing on a trait to his daughter

B. Two affected parents having an unaffected child

C. Two unaffected parents having an affected child

D. All the children of affected parents are affected

Indicate the genotypes of the individuals in the pedigree chart below by placing AA, Aa, or aa below the squares and circles.

Galactosemia is a disorder that results from the inheritance of two recessive alleles (ex. aa genotype). Indicate the possible genotypes of the individuals in the pedigree chart below by placing AA, Aa, or aa below the squares and circles.

Hemophelia is an X-Linked recessive trait. A woman who does not have hemophelia, has a father that does. If she has children with another man who does not have hemophelia, what is the chance (in a percent) that she has a child with the disease?

If a man with full color vision has a child with a woman with a full color vision whose father was red-green color blind (cb), what is the probability that their first child is colorblind?

A. 1/2

B. 1/3

C. 1/4

D. 1/6

E. 1/8

Look at the pedigree shown. What is the most likely pattern of inheritance for this trait?

A. X-linked dominant

B. X-linked recessive

C. Autosomal dominant

D. Autosomal recessive.

Consider the following pedigree of a rare autosomal recessive disease. Assume all people marrying into the pedigree do not carry the abnormal allele.

a) If individuals A and B have a child, what is the probability that the child will have the disease?

b) If the first child of C * D has the disease, what is the probability that their second child will have teh disease?

Retinitis pigmentosum (RP) is a rare inherited condition that eventually results in the loss of night vision. The pedigrees below describe three families with a history of RP.

a. Explain from the pedigrees of Families A, B, and C how RP is inherited. Be sure you can account for all individuals.

Joshua, age 18, is color blind. His mother and father have normal vision, but his mother's father (Joshua's maternal grandfather) is color blind. All Joshua's other grandparents have normal color vision. Joshua has three sisters - Nikki (age 20), Shaneekwa (age 15), and Laticia (age 27), all with normal color vision. Joshua's oldest sister, Latecia, is married to a man with normal color vision; they have two children: a 9-year old color blind boy and a 4-year old girl with normal color vision.

Using correct symbol, annotation, and rules for pedigree construction, draw a pedigree of Joshua's family.

Which of the choices below is a characteristic of the pedigree of a dominant trait?

A. From matings in which one parent is affected, approximately half of the offspring are affected.

B. The trait will appear in offspring of unaffected parents.

C. The trait often will skip a generation.

D. All of these choices are correct.

John and Sue are expecting a child, but are concerned about a rare autosomal recessive disease that is present in both of their families. In the pedigree below, John is represented as individual III-11 and Sue is represented as individual III-12. John's sister, III-10, and Sue's brother, III-13, both do not show evidence of the disease, but John's paternal grandmother and Sue's maternal grandfather both had the disease.

What is the probability that John is a carrier?

What is the probability that both John and Sue are carriers?

Alpers' disease is a mitochondrially inherited disease with symptoms that include seizures, dementia, blindness, liver dysfunction, and cerebral degeneration. The pedigree below shows the presence of Alpers' disease in three generations. Individual 4had one daughter and two sons, and individual 6 had two daughters and one son.

Which of the individuals indicated below are affected by Alpers' disease? Place the correct symbols on the pedigree showing affected and unaffected individuals.

Suppose that Jess has mycotonic dystrophy and shows traits such as uncontrolled muscle activity. Jess's mother, Rose, is dystrophic, but her father is normal. Jess is married to Dave, and Dave is normal. Jess and Dave have a daughter, Lisa, and two sons, Phil and Erik. Lisa and Phil are normal, but Erik is dystrophic. Jess's sister, Jill is normal. Jill's husband and their only child are also normal. Jess's brother, Pete is dystrophic, and has three children with Mary, who is normal. Pete and Mary have two daughters, Judy and Pat, as well as a son, Carl. Judy is normal, but Pat and Carl are dystrophic.

Label six of the pedigree symbols with the corresponding names of the individuals in Jess' family.

Huntington's disease, which causes degeneration of neurons, runs in Maria's family. Huntington's is a heritable autosomal dominant genetic disease. Family members that have the disease include Maria's paternal grandmother and Maria's paternal uncles. Maria's paternal grandfather does not have the disease.

Because symptoms of Huntington's disease do not appear until later in life, genetic testing is necessary to determine whether a younger individual possesses the allele for the disease. These tests determined that Maria's father does not carry the allele for Huntington's disease.

Maria's maternal uncle suggested that Maria create a pedigree to track the disease in her family. Use the symbols provided to complete the pedigree.

If a male with an X-linked recessive disease mates with a female who is a carrier for the disease, what percentage of their male and female offsprings will be affected?

A husband and wife have normal vision, although both of their fathers are red-green color-blind, an inherited X-linked recessive condition.

A. Give the genotypes of the husband and wife.

B. What is the probability that their first child will be:

B.1. a normal son?

B.2. A normal daughter?

B.3. A color-blind son?

B.4. A color-blind daughter?

The pedigree shown below is typical of :

A. An autosomal dominant mutation.

B. An autosomal recessive mutation

C. An X-linked mutation

D. A mitochondrial mutation

E. None of the answers listed above are correct.

The enzyme glucose-6-phosphate dehydrogenase (G6PD) deficiency is inherited as a recessive gene on the X-chromosome in humans. Below is a pedigree of a family affected by G6PD. 

II-2 has a child with a man that is not affected by G6PD deficiency. She is pregnant with their first child. Genetic tests that her child is a boy. What is the probability that her male child will have G6PD deficiency?

A. 0

B. 1/4

C. 1/2

D. 3/4

E. 1

Red-green color blindnessis an X-linked recessive trait in humans. Polydactyly (extra fingers and toes) is an autosomal dominant trait. Martha has normal fingers and toes and normal color vision. Her mother is normal in all respects, but herfather is color blind and polydactylous. Bill is color blind and polydactylous.

If Bill and Martha marry, what proportions of children with specific phenotypes would they be expected to produce? The answers only include the proportions of some of the possible phenotypes; other phenotypes are also expected to occur but are not included.

A. 1/4 color-blind girls with normal fingers, 1/4 boys with normal vision and polydactyly

B. 1/4 girls with normal vision and polydactyly, 1/8 boys with normal vision and polydactyly

C. 1/8 color-blind girls with normal fingers, 1/4 boys with normal vision and polydactyly

D. 1/8 color-blind girls with polydactly, 1/8 boys with normal vision and normal fingers

Five generations back, you have learned that your great great grandmother had a rare autosomal recessive disease that is manifested by the strange condition in which the eating of celery leads to immediate, violent vomiting (chronic susceptibility; CCS). None of the individuals leading to you have had CCS, but it is not known if any of them were carriers. Draw a pedigree and calculate the probability that you are a carrier of the recessive CCS allele.

Assume that this pedigree reflects the inheritance of an autosomal recessive disease allele. Use 'a' for the recessive allele and 'A' for the corresponding dominant wild type, normal allele. Neither of the two parents has the disease so they were surprised when one of their children (II-4) showed the disease symptom. Child II.5 is yet to be born, neither the sex nor the disease condition of the future child is known.

a) Assign genotypes to all individuals in the pedigree. Use A- for individuals that you know lack the disease that might be either heterozygous or homozygous dominant.

b) You know that individuals II-1, II-3, and II-4 lack the disease but that they may either be homozygotes or heterozygotes. Given just these two possibilities, what is the chance that these 3 individuals are homozygous dominant?

c) What is the chance that individuals II-1, II-3, and II-4 are heterozygous carriers?

d) For indicidual II-5, about which we know nothing, what is the chance of exhibiting the disease? Being homozygous dominant (disease allele free)? Being heterozygous carrier?

Hemopphilia is an X-linked recessive disorder in humans. If a heterozygous woman has children with an unaffected man, what are the odds of the following combinations of children?

A. An affected son.

B. Four unaffected offspring in a row.

C. An unaffected daughter or son.

D. Three out of five offspring that are affected

Examine the pedigree below:

a) What is the inheritance pattern of this disorder? Justify your answer.

b) What is the probability that BOTH of the daughter IV-1 and IV-4 are carriers of the disorder?

c) What is the probability that BOTH of the daughters IV-5 and IV-8 are carriers of the disorder?

If two parents who are heterozygous for eye color mate, what is the probability their first two children will have blue eyes (assume they do not have identical twins)? 

NOTE: In humans, the brown eye color allele (B) is dominant to the allele for blue eye color (b).

A. 1/1

B. 1/2

C. 1/4

D. 1/16

Ann's family has a history of cystic fibrosis, a recessive genetic disease. In the pedigree below, family members who are afflicted with the disease are shown in red. Members who are unafflicted may or may not be carriers. Which of the given family members can be identified definitively as unafflicted carriers of cystic fibrosis?

Briefly define the terms "linkage map", "physical map" and "karyotypic map". What techniques could be used to allow you to determine the position on a polymorphic DNA character to each of these maps?

Consider this hypothetical pedigree for a sex-linked recessive trait.

Can you say for certain what the genotype is for:

a) the mother

b) the daughter

Consider the following family history: A man with a widow's peak and normal color vision marries a color-blind woman with a straight hairline. The man's father had a straight hairline, as did both of the woman's parents. Use the family history to make predictions about the couple's children. Choose the correct label to the appropriate location in the table.  Not all labels will be used. 

What is the genotype of a man who has freckles (dominant) and is color-blind, if his mother lacked freckles?

A man with a widow’s peak, whose mother was color blind and whose father had a continuous hairline, is engaged to marry a woman whose color blind mother had a continuous hairline, and whose normal visioned father had a continuous hairline.

a. what is the genotype of the young gentleman?

b. What is the genotype of his fiancée?

If the couple in the preceding problem marry and have a family, what are the chances of them having:

a. A normal visioned child with a continuous hairline?

b. A color blind child with a widow’s peak?

c. A normal visioned daughter with a continuous hairline?

d. A color blind son with a widow’s peak?

In one of Morgan’s experiments, he crossed his newly discovered white-eyed male with a red-eyed female. (Note that all of the females at that time were homozygous for red eyes because the allele for white eyes had not yet propagated through Morgan’s flies.) All of the F₁ flies produced by this cross (both males and females) had red eyes.

Next, Morgan crossed the red-eyed F₁ males with the red-eyed F₁ females to produce an F₂ generation. The Punnett square below shows Morgan’s cross of the F₁ males with the F₁ females.

Drag the labels to their appropriate locations to complete the Punnett square for Morgan’s F₁ x F₁ cross.

• Drag pink labels onto the pink targets to indicate the alleles carried by the gametes (sperm and egg).
• Drag blue labels onto the blue targets to indicate the possible genotypes of the offspring.

Labels can be used once, more than once, or not at all.

Below is a pedigree chart illustrating the transmission of hemophilia in the royal family of England.  

Evaluate the pedigree and determine how such is transmitted within this family. Does the transmission rate seem high or low in comparison to what you know about different forms of transmission, mutations, etc.?  

The result of the following cross indicates that the genotype of the male parent is _____. (Using B as the wild type allele and b for the flat head allele)

a. Bb
b. B
c. BB
d. b
e. bb

If B represents the allele for black eyes (dominant) and b represents the allele for orange eyes (recessive), what would be the phenotypic ratio of a cross between a homozygous black-eyed alien and an orange-eyed alien?

(Express your answers using only the numbers with the dominant first and recessive second. For example: 3 black eyes : 1 orange eyes would be just 3:1)

A man with a type A blood marries a woman with type B blood. Their child has type O blood. What are the genotypes of these individuals? What other genotypes, and in what frequencies, would you expect in offspring from this marriage?

Which of the following is LEAST likely to be a health problem for someone with cystic fibrosis?

a. nutritional deficiencies
b. diabetes
c. frequent infections
d. obesity

The allele that causes cystic fibrosis is recessive. An individual who is heterozygous for cystic fibrosis

a. is a carrier.
b. cannot reproduce.
c. will have children who are all carriers of cystic fibrosis.
d. cannot have children with cystic fibrosis.

Sophie has cystic fibrosis. If Sophie conceives a child, and the father neither has cystic fibrosis nor is a carrier, what are the chances that the child would have cystic fibrosis?

a. 25%, because only one in four gametes will carry the bad gene
b. 50%, because there is a 50% chance that Sophie will pass along the bad gene
c. 100%, because Sophie has the condition
d. 75%, because Sophie has the condition but the father does not
e. 0%, because the child must receive the bad gene from both parents

Sophie's parents are carriers for cystic fibrosis. If Sophie has a brother or sister from the same parents, what are the chances that the sibling would have cystic fibrosis?

a. 50%
b. 100%
c. 75%
d. 25%
e. 0%

If the shaded phenotype in the pedigree above is caused by an autosomal dominant allele, then what is the chance that individuals labeled 4 & 5 (in row II) will have an unafflicted (unshaded) daughter?

a. 100%

b. 25%

c. 50%

d. 75%

e. it cannot be determined from the information provided

The pedigree above could be explained by an X-linked dominant inheritance pattern.

a. True

b. False

Assume that in cats, a crooked tail is caused by an autosomal recessive allele. A male and female cat, each with normal tails, have previously had a litter of kittens in which some kittens had crooked tails. What is the probability that the same two parents will next produce two normal females or two males with crooked tails?

a. 5/8

b. 9/16

c. 9/32

d. 9/64

e. 5/32

The pedigree in the figure shows the transmission of a trait in a particular family. Based on this pattern of transmission, the trait is most likely X-linked dominant.

a. True

b. False

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. 9/16

b. 3/4

c. 1/16

d. 1/2

e. 1/8

Because you have some basic knowledge of genetics, a young woman (A, below) has come to you for help. She has a brother who has a disease, but her parents and all of her husband's family are normal. She has a two-year-old daughter who shows the disease of her brother. She is now pregnant and is fearful that the next child will also have the disease. Can you help her by answering the questions below?

i) What is the probability that her second child will have the disease?

ii) If the second child is a boy, what is the probability that he will have the disease?

The inheritance of a particular facial hair pattern in a given family is indicated below. Answer the following questions about this family tree.

Given the family history below for the inheritance of a skin abnormality in humans, what is the correct mechanism of inheritance for this abnormality?

The following pedigree shows the presence of individuals bearing extra fingers and toes--exhibiting "polydactyly." Explain the genetic mechanism for the inheritance of this trait in the family.

Research has shown that a particular eye defect is represented in a family pedigree as shown below:

i) On the basis of this data, which of the following mechanisms of inheritance are POSSIBLE? autosomal dominant, autosomal recessive, sex-linked dominant, sex-linked recessive, Y-linked.

ii) What is the most PROBABLE mechanism of inheritance?

iii) What is the genotype of female A?

iv) What is the genotype of male B?

v) What is the probability that a child from marriage C will show this eye defect?

In humans, dark hair (B) is dominant over blondness (b), and color blindness (c) is a sex-linked recessive trait. A women has a blond brother, a blond mother, and a dark-haired father. Her brother and her parents have normal vision. She bears the following three children by her blond, normal-visioned husband:

a dark-haired son with normal vision,

a dark-haired daughter with normal vision, and

a dark-haired color-blind son

i) Make a pedigree of the entire family showing the probable genotypes of all individuals.

ii) What is the probability that her next (fourth) child will be a color-blind boy?

iii) If her fourth child is a boy, what is the probability that he will have dark hair?

iv) What is the chance that her next four children will all be girls?

The individuals in the above pedigree that are dark have ‘blue’ coat color. How is it transmitted? Note that the blue coated individual in the second generation has three different mates.

a) a dominant allele

b) recessive allele

c) codominant allele

d) multiple alleles

What is an important limitation of pedigree analysis in studying the inheritance many complex traits?

a. many traits are not influenced by genes

b. many traits are influenced by many loci

c. many traits are influenced by the environment

d. many traits are only found in some family members

e. both b and c 

Which of the following are potential advantages of genetic testing for inherited diseases?

a. individuals can make informed decisions about reproduction

b. individuals have a greater sense of certainty about their own health

c. any possible treatment can be started at an earlier age

d. choices A & B only

e. choices A, B and C

Which of the following is a problem faced by scientists studying human genetics but not by scientists studying plant genetics?

a. Inability to do controlled crosses

b. Lack of interest from funding agencies

c. Shared environment of parents and offspring

d. The research is too costly

How is the trait shown by the dark squares being inherited?

a. dominant (autosomal) 

b. recessive (autosomal) 

c. X-linked recessive

d. X-linked dominant  

In order for a girl to inherit hemophilia A, her parents would have which genotypes? 

a. XH XH, Xh Y

b. XH Xh, XH Y

c. XH XH, XH Y

d. XH Xh, Xh Y

e. Xh Xh, XH Y

Hemophilia A is an X-linked recessive disorder. If a normal man marries a woman who is a carrier, what fraction of their daughters will have hemophilia? 

a. 25%

b. 50%

c. 0%

d. 100%

e. 75%

Hemophilia A is an X-linked recessive disorder. If a normal man marries a woman who is a carrier, what fraction of their sons will have hemophilia? 

a. 50%

b. 25%

c. 0%

d. 100%

e. 75%

In Huntington disease, a child will typically only get the disease if one parent also has it. It is as common in boys as in girls. This disease is: 

a. Autosomal recessive

b. X-linked recessive

c. X-linked dominant

d. Autosomal dominant

e. Pleiotropic

In cystic fibrosis, two unaffected carriers can have a child with the disease. It is as common in boys as in girls. This disease is: 

a. Autosomal dominant

b. X-linked recessive

c. Autosomal recessive

d. X-linked dominant

e. Pleiotropic

Females who are "carriers" for hemophilia: 

a. Theoretically pass the allele for hemophilia to half of their offspring

b. Theoretically pass the allele for hemophilia to half of their daughters who become at least "carriers" for this disorder

c. All are correct

d. Theoretically pass the allele for hemophilia to half of their sons who become hemophiliacs

e. Usually do not show any symptoms of hemophilia

In pedigree charts, autosomal recessive disorders typically: 

a. Appear in every generation

b. Appear only in males

c. Appear only in females

d. Seem to disappear in one generation, only to reappear in the next generation

e. Occur every third generation

In pedigree charts, autosomal dominant disorders typically: 

a. Appear only in males

b. Appear only in females

c. Appear in every generation

d. Seem to disappear in one generation, only to reappear in the next generation

e. Occur every third generation

Diagrams depicting family relationships and phenotypes for a genetic disorder are: 

a. Linkage maps

b. Pedigree charts

c. Karyotypes

d. Punnett squares

e. Bell-shaped curves

If a person has a recessive allele for a disease and that allele is masked by a normal dominant allele, this person: 

a. Homozygous for the disease

b. Cannot produce gametes

c. Is termed a "carrier"

d. Is termed a linkage group

e. Has the disease but cannot pass this disease to their offspring

To inherit an autosomal recessive disorder requires a person to receive the disease causing allele from: 

a. The father only

b. The mother only

c. Only the parent having the disease

d. Only one parent who is homozygous recessive for the disease

e. Both parents

To inherit an autosomal dominant disorder a person could receive the disease causing allele from: 

a. The father only, not the mother

b. The mother only, not the father

c. The mother or the father

d. The parent who does not exhibit the disease

e. All are correct

Recessive alleles seem to vanish in some generations and reappear in later generations because: 

a. They cannot be expressed in males

b. They are masked by a dominant allele

c. They cannot be expressed in females

d. They cannot be expressed in successive generations

e. They are lost by mutation

A healthy young couple are both carriers of cystic fibrosis, the chance that each of their future children will inherit this serious illness is: 

a. 0%, because cystic fibrosis is not an inherited illness

b. 25%

c. 10%

d. 50%

e. 100%

Use the pedigree diagram below to answer the following question. Blue toes is an autosomal recessive trait.

What is the genotype of the female in generation I?