Match each statement (a–e) with the best answer from the following list: consultand, 50%, prior probability, 66.7%, obligate carrier, 100%.

The probability that the son of a woman with an autosomal recessive condition is a heterozygous carrier

Match each statement (a–e) with the best answer from the following list: consultand, 50%, prior probability, 66.7%, obligate carrier, 100%.

The person receiving genetic counseling

Match each statement (a–e) with the best answer from the following list: consultand, 50%, prior probability, 66.7%, obligate carrier, 100%.

The probability that the healthy brother of a woman with an autosomal recessive condition is a heterozygous carrier

Match each statement (a–e) with the best answer from the following list: consultand, 50%, prior probability, 66.7%, obligate carrier, 100%.

A person who on the basis of family history must be a heterozygous carrier of a recessive mutant allele

Match each statement (a–e) with the best answer from the following list: consultand, 50%, prior probability, 66.7%, obligate carrier, 100%.

The Mendelian risk that a person is a heterozygous carrier of a recessive condition

A couple comes into your genetic counseling practice with a question about the chance a future child of theirs might have a genetic disease. Three or four men in the woman's family, including her father, had a condition that might be genetic. Although her father is still alive, she has had little contact with him for much of her life and cannot describe or name the condition. Her partner is a healthy man whose family has no history indicating the presence of a genetic condition. To provide more information about this possible genetic condition for the couple, what is the first step you recommend?

In mice, black coat color is dominant to white coat color. In the pedigree shown here, mice with a black coat are represented by darkened symbols, and those with white coats are shown as open symbols. Using allele symbols B and b, determine the genotypes for each mouse. 

Nail–patella syndrome is an autosomal disorder affecting the shape of nails on fingers and toes as well as the structure of kneecaps. The pedigree below shows the transmission of nail–patella syndrome in a family along with ABO blood type.

Explain why III-6 has nail–patella syndrome and III-8 does not. Give genotypes for these two individuals.

Nail–patella syndrome is an autosomal disorder affecting the shape of nails on fingers and toes as well as the structure of kneecaps. The pedigree below shows the transmission of nail–patella syndrome in a family along with ABO blood type.

Using N and n to represent alleles at the nail–patella locus and Iᴬ, Iᴮ and i to represent ABO alleles, write the genotypes of I-1 and I-2 as well as their five children in generation II.

Consider this human pedigree for a vision defect.

What is the most probable mode of inheritance of the disease? Identify any discrepancies between the pedigree and your proposed mode of transmission, and provide possible explanations for these exceptions. 

The accompanying pedigree shows the transmission of albinism (absence of skin pigment) in a human family.

One child of female I-3 has albinism. What is the probability that any of the other four children are carriers of the allele for albinism? 

The accompanying pedigree shows the transmission of albinism (absence of skin pigment) in a human family.

What is the probability that female I-3 is a heterozygous carrier of the allele for albinism? 

The accompanying pedigree shows the transmission of albinism (absence of skin pigment) in a human family.

The female I-1 and her mate, male I-2, had four children, one of whom has albinism. What is the probability that they could have had a total of four children with any other outcome except one child with albinism and three with normal pigmentation? 

The accompanying pedigree shows the transmission of albinism (absence of skin pigment) in a human family.

Using allelic symbols of your choice, identify the genotypes of the male and his two mates in generation I. 

The accompanying pedigree shows the transmission of albinism (absence of skin pigment) in a human family.

What is the most likely mode of transmission of albinism in this family? 

(a) In humans the mitochondrial genome encodes a low number of proteins, rRNAs, and tRNAs but imports approximately 1100 proteins encoded by the nuclear genome. Yet, with such a small proportion from the mitochondrial genome encoding proteins and RNAs, a disproportionately high number of genetic disorders due to mtDNA mutations have been identified [Bigger, B. et al. (1999)]. What inheritance pattern would you expect in a three-generation pedigree in which the grandfather expresses the initial mtDNA defect? What inheritance pattern would you expect in a three-generation pedigree in which the grandmother expresses the initial mtDNA defect? (b) Considering the description in part (a) above, how would your pedigrees change if you knew that the mutation that caused the mitochondrial defect was recessive and located in the nuclear genome, was successfully transported into mitochondria, and negated a physiologically important mitochondrial function?

The following pedigree shows a family in which several individuals exhibit symptoms of the mitochondrial disease MERRF. Two siblings (II-2 and II-5) approach you to inquire about whether their children will also be afflicted with MERRF. What do you tell them? 

What is the most likely mode of inheritance for the trait depicted in the following human pedigree? 

Researchers examined a family with an interesting distribution of Leigh syndrome symptoms. In this disorder, individuals may show a progressive loss of motor function (ataxia, A) with peripheral neuropathy (PN, meaning impairment of the peripheral nerves). A mitochondrial DNA (mtDNA) mutation that reduces ATPase activity was identified in various tissues of affected individuals. The accompanying table summarizes the presence of symptoms in an extended family.

Person                 Condition           Percent Mitochondria with
                                                       Mutation
Proband                A and PN            >90%
Brother                  A and PN            >90%
Brother                  Asymptomatic      17%
Mother                   PN                       86%
Maternal uncle       PN                       85%
Maternal cousin     A and PN             90%
Maternal cousin     A and PN             91%
Maternal                Asymptomatic      56%
grandmother


In what way does a condition caused by mtDNA differ in expression and transmission from a mutation that causes albinism?

Researchers examined a family with an interesting distribution of Leigh syndrome symptoms. In this disorder, individuals may show a progressive loss of motor function (ataxia, A) with peripheral neuropathy (PN, meaning impairment of the peripheral nerves). A mitochondrial DNA (mtDNA) mutation that reduces ATPase activity was identified in various tissues of affected individuals. The accompanying table summarizes the presence of symptoms in an extended family.

Person                 Condition           Percent Mitochondria with
                                                       Mutation
Proband                A and PN            >90%
Brother                  A and PN            >90%
Brother                  Asymptomatic      17%
Mother                   PN                       86%
Maternal uncle       PN                       85%
Maternal cousin     A and PN             90%
Maternal cousin     A and PN             91%
Maternal                Asymptomatic      56%
grandmother


How can some individuals in the same family show such variation in symptoms? What term, as related to organelle heredity, describes such variation?

Researchers examined a family with an interesting distribution of Leigh syndrome symptoms. In this disorder, individuals may show a progressive loss of motor function (ataxia, A) with peripheral neuropathy (PN, meaning impairment of the peripheral nerves). A mitochondrial DNA (mtDNA) mutation that reduces ATPase activity was identified in various tissues of affected individuals. The accompanying table summarizes the presence of symptoms in an extended family.

Person                 Condition           Percent Mitochondria with
                                                       Mutation
Proband                A and PN            >90%
Brother                  A and PN            >90%
Brother                  Asymptomatic      17%
Mother                   PN                       86%
Maternal uncle       PN                       85%
Maternal cousin     A and PN             90%
Maternal cousin     A and PN             91%
Maternal                Asymptomatic      56%
grandmother


Provide an explanation for the pattern of inheritance of the disease. What term describes this pattern?

Researchers examined a family with an interesting distribution of Leigh syndrome symptoms. In this disorder, individuals may show a progressive loss of motor function (ataxia, A) with peripheral neuropathy (PN, meaning impairment of the peripheral nerves). A mitochondrial DNA (mtDNA) mutation that reduces ATPase activity was identified in various tissues of affected individuals. The accompanying table summarizes the presence of symptoms in an extended family.

Person                 Condition           Percent Mitochondria with
                                                       Mutation
Proband                A and PN            >90%
Brother                  A and PN            >90%
Brother                  Asymptomatic      17%
Mother                   PN                       86%
Maternal uncle       PN                       85%
Maternal cousin     A and PN             90%
Maternal cousin     A and PN             91%
Maternal                Asymptomatic      56%
grandmother


Develop a pedigree that summarizes the information presented in the table.

For each pedigree shown,

Determine which other pattern(s) of transmission is/are possible. For each possible mode of transmission, specify the genotypes necessary for transmission to occur. <>

The accompanying pedigree shows the transmission of a phenotypic character. Using B to represent a dominant allele and b to represent a recessive allele,

Give the genotype(s) possible for each member of the family, assuming the trait is autosomal recessive. 

The accompanying pedigree shows the transmission of a phenotypic character. Using B to represent a dominant allele and b to represent a recessive allele,

Give the genotype(s) possible for each member of the family, assuming the trait is autosomal dominant. 

Galactosemia is an autosomal recessive disorder caused by the inability to metabolize galactose, a component of the lactose found in mammalian milk. Galactosemia can be partially managed by eliminating dietary intake of lactose and galactose. Amanda is healthy, as are her parents, but her brother Alonzo has galactosemia. Brice has a similar family history. He and his parents are healthy, but his sister Brianna has galactosemia. Amanda and Brice are planning a family and seek genetic counseling. Based on the information provided, complete the following activities and answer the questions.

Draw a pedigree that includes Amanda, Brice, and their siblings and parents. Identify the genotype of each person, using G and g to represent the dominant and recessive alleles, respectively.

Draw a pedigree containing two parents and four children. Both of the parents have AB blood type. The first child is type A, the second child is type AB, and the third child is type B.

What is the name of the genetic phenomenon producing this observation?

Alkaptonuria is an infrequent autosomal recessive condition. It is first noticed in newborns when the urine in their diapers turns black upon exposure to air. The condition is caused by the defective transport of the amino acid phenylalanine through the intestinal walls during digestion. About 4 people per 1000 are carriers of alkaptonuria.
Sara and James had never heard of alkaptonuria and were shocked to discover that their first child had the condition. Sara's sister Mary and her husband, Frank, are planning to have a family and are concerned about the possibility of alkaptonuria in one of their children.
The four adults (Sara, James, Mary, and Frank) seek information from a neighbor who is a retired physician. After discussing their family histories, the neighbor says, 'I never took genetics, but I know from my many years in practice that Sara and James are both carriers of this recessive condition. Since their first child had the condition, there is a very low chance that the next child will also have it, because the odds of having two children with a recessive condition are very low. Mary and Frank have no chance of having a child with alkaptonuria because Frank has no family history of the condition.' The two couples each have babies and both babies have alkaptonuria.

What was incorrect about the information given to Sara and James? What is incorrect about the information given to Mary and Frank?

Alkaptonuria is an infrequent autosomal recessive condition. It is first noticed in newborns when the urine in their diapers turns black upon exposure to air. The condition is caused by the defective transport of the amino acid phenylalanine through the intestinal walls during digestion. About 4 people per 1000 are carriers of alkaptonuria.
Sara and James had never heard of alkaptonuria and were shocked to discover that their first child had the condition. Sara's sister Mary and her husband, Frank, are planning to have a family and are concerned about the possibility of alkaptonuria in one of their children.
The four adults (Sara, James, Mary, and Frank) seek information from a neighbor who is a retired physician. After discussing their family histories, the neighbor says, 'I never took genetics, but I know from my many years in practice that Sara and James are both carriers of this recessive condition. Since their first child had the condition, there is a very low chance that the next child will also have it, because the odds of having two children with a recessive condition are very low. Mary and Frank have no chance of having a child with alkaptonuria because Frank has no family history of the condition.' The two couples each have babies and both babies have alkaptonuria.

What are the genotypes of the four adults?

The accompanying pedigree shows a family in which one child (II-1) has an autosomal recessive condition. On the basis of this fact alone, provide the following information.

What is the chance that among the three children in generation II who have the dominant phenotype, one of them is AA and two of them are Aa? (Hint: Consider all possible orders of genotypes.)

The accompanying pedigree shows a family in which one child (II-1) has an autosomal recessive condition. On the basis of this fact alone, provide the following information.

What is the probability that all three of the children in generation II who have the dominant phenotype are Aa?

The accompanying pedigree shows a family in which one child (II-1) has an autosomal recessive condition. On the basis of this fact alone, provide the following information.

What are the probabilities for each of the possible genotypes for II-2, II-3, and II-4?

The accompanying pedigree shows a family in which one child (II-1) has an autosomal recessive condition. On the basis of this fact alone, provide the following information.

Using the same alleles, give the possible genotypes for II-2, II-3, and II-4. <>

The accompanying pedigree shows a family in which one child (II-1) has an autosomal recessive condition. On the basis of this fact alone, provide the following information.

Using A for the dominant allele and a for the recessive allele, give the genotypes for I-1, I-2, and II-1. <>

Select a human hereditary disease or condition you would like to know more about. Using the OMIM website (http://www.ncbi.nlm.nih.gov/omim), search for the disease and prepare a short synopsis of your findings. Include the following information:

Any available information about the population(s) in which the disease is most common.

For a number of human hereditary conditions, genetic testing is available to identify heterozygous carriers. Some heterozygous carrier testing programs are community-based, often as part of an organized effort targeting specific populations in which a disease and carriers of a disease are relatively frequent. For example, carrier genetic testing programs for Tay–Sachs disease target Ashkenazi Jewish populations and sickle cell disease carrier testing programs target African American populations. The testing is usually free or available at minimal cost, the wait time for results is short, and the results are confidential and unavailable to third parties such as insurance companies. Neither the Tay–Sachs nor the sickle cell allele produces serious consequences for heterozygous carriers.

From a genetic perspective, what is the value of the information obtained by genetic testing of the type described?

For a number of human hereditary conditions, genetic testing is available to identify heterozygous carriers. Some heterozygous carrier testing programs are community-based, often as part of an organized effort targeting specific populations in which a disease and carriers of a disease are relatively frequent. For example, carrier genetic testing programs for Tay–Sachs disease target Ashkenazi Jewish populations and sickle cell disease carrier testing programs target African American populations. The testing is usually free or available at minimal cost, the wait time for results is short, and the results are confidential and unavailable to third parties such as insurance companies. Neither the Tay–Sachs nor the sickle cell allele produces serious consequences for heterozygous carriers.

Do you personally think you would participate in the kind of carrier genetic testing described if you were a member of a population targeted for such testing?

For a number of human hereditary conditions, genetic testing is available to identify heterozygous carriers. Some heterozygous carrier testing programs are community-based, often as part of an organized effort targeting specific populations in which a disease and carriers of a disease are relatively frequent. For example, carrier genetic testing programs for Tay–Sachs disease target Ashkenazi Jewish populations and sickle cell disease carrier testing programs target African American populations. The testing is usually free or available at minimal cost, the wait time for results is short, and the results are confidential and unavailable to third parties such as insurance companies. Neither the Tay–Sachs nor the sickle cell allele produces serious consequences for heterozygous carriers.

In a broader sense, what is the value of a community-based effort targeting specific populations for selected diseases?

In humans, the ability to bend the thumb back beyond vertical is called hitchhiker's thumb and is dominant to the inability to do so (OMIM 274200; see Problem 41). Also, the presence of attached earlobes is recessive to unattached earlobes (OMIM 128900).

Using all available and willing members of your family, or members of another family if yours is not easily accessible, trace the transmission of both traits in a pedigree. Use allelic symbols H and h for the thumb and E and e for earlobes, and identify the genotypes for each family member as completely as possible. Bring the pedigree back to share with your group.

In humans, the ability to bend the thumb back beyond vertical is called hitchhiker's thumb and is dominant to the inability to do so (OMIM 274200; see Problem 41). Also, the presence of attached earlobes is recessive to unattached earlobes (OMIM 128900).

Check your own phenotype and those of several friends or classmates.

This pedigree exhibits which of the following inheritance patterns?  

This pedigree exhibits which of the following inheritance patterns? 

This pedigree exhibits which of the following inheritance patterns?