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Problem 1
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 conditionProblem 1
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 alleleProblem 1
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 carrierProblem 1
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 counselingProblem 1
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 carrierProblem 1
Reciprocal crosses of experimental animals or plants sometimes give different results in the . What are two possible genetic explanations? How would you distinguish between these two possibilities (i.e., what crosses would you perform, and what would the results tell you)?
Problem 1
Compare and contrast the following terms:
monohybrid cross and test crossProblem 1
Compare and contrast the following terms:
dihybrid cross and trihybrid crossProblem 1
For parts (a), (b), and (c) of this problem, draw a diagram illustrating the alleles on homologous chromosomes for the genotypes given, assuming in each case that the genes reside on the chromosome in the order written. For parts (d) and (e), give the information requested.
AB/abProblem 1
For parts (a), (b), and (c) of this problem, draw a diagram illustrating the alleles on homologous chromosomes for the genotypes given, assuming in each case that the genes reside on the chromosome in the order written. For parts (d) and (e), give the information requested.
aBc/abCProblem 1
For parts (a), (b), and (c) of this problem, draw a diagram illustrating the alleles on homologous chromosomes for the genotypes given, assuming in each case that the genes reside on the chromosome in the order written. For parts (d) and (e), give the information requested.
DFg/DFGProblem 1
For parts (a), (b), and (c) of this problem, draw a diagram illustrating the alleles on homologous chromosomes for the genotypes given, assuming in each case that the genes reside on the chromosome in the order written. For parts (d) and (e), give the information requested.
the gametes produced by an organism with the genotype Rt/rTProblem 1
For parts (a), (b), and (c) of this problem, draw a diagram illustrating the alleles on homologous chromosomes for the genotypes given, assuming in each case that the genes reside on the chromosome in the order written. For parts (d) and (e), give the information requested.
progeny of the cross Rt/rT×rt/rtProblem 1
Compare and contrast the terms in each of the following pairs:
a polymorphic trait and a polymorphic geneProblem 2
For the cross BB×Bb, what is the expected genotype ratio? What is the expected phenotype ratio?
Problem 3
For the cross Aabb×aaBb, what is the expected genotype ratio? What is the expected phenotype ratio?
Problem 3
For the retinal cancer retinoblastoma, the inheritance of one mutated copy of RB1 from one of the parents is often referred to as a mutation that produces a 'dominant predisposition to cancer.' This means that the first mutation does not produce cancer but makes it very likely that cancer will develop.
Using RB1⁺ for the normal wild-type allele and RB1⁻ for the mutant allele, identify the genotype of a cell in a retinoblastoma tumor.Problem 3
For the retinal cancer retinoblastoma, the inheritance of one mutated copy of RB1 from one of the parents is often referred to as a mutation that produces a 'dominant predisposition to cancer.' This means that the first mutation does not produce cancer but makes it very likely that cancer will develop.
What is the genotype of a normal cell in the retina in a person who has sporadic retinoblastoma? What is the normal cell genotype if the person has hereditary retinoblastoma? Explain the reason for the difference between the genotypes.Problem 3
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?
Problem 3
A pure-breeding tall plant producing oval fruit as described in Problem 2 is crossed to a pure-breeding short plant producing round fruit.
The F₁ are crossed to short plants producing oval fruit. What are the expected proportions of progeny phenotypes?Problem 3
A pure-breeding tall plant producing oval fruit as described in Problem 2 is crossed to a pure-breeding short plant producing round fruit.
If the F₁ identified in part (a) are crossed to one another, what proportion of the F₂ are expected to be short and produce round fruit? What proportion are expected to be tall and produce round fruit?Problem 4
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.
Problem 4
A man, J.B., has a sister with autosomal recessive galactosemia (OMIM 230400), and his partner, S.B., has a brother with galactosemia. Galactosemia is a serious condition caused by an enzyme deficiency that prevents the metabolism of the sugar galactose. Neither J.B. nor S.B. has galactosemia, but they are concerned about the risk that a future child of theirs will have the condition. What is the probability their first child will have galactosemia?
Problem 5
Two parents plan to have three children. What is the probability that the children will be two girls and one boy?
Problem 5
A woman, S.R., had a maternal grandfather with hemophilia A (OMIM 306700), an X-linked recessive condition that reduces blood clotting. S.R.'s maternal grandmother and paternal grandparents are free of the condition, as are her partner, his parents, and his grandparents. S.R. has no siblings. She wants to know the chance that a son of hers will have the condition. What is that probability?
Problem 5
In a type of parakeet known as a 'budgie,' feather color is controlled by two genes. A yellow pigment is synthesized under the control of a dominant allele Y. Budgies that are homozygous for the recessive y allele do not synthesize yellow pigment. At an independently assorting gene, the dominant allele B directs synthesis of a blue pigment. Recessive homozygotes with the bb genotype do not produce blue pigment. Budgies that produce both yellow and blue pigments have green feathers; those that produce only yellow pigment or only blue pigment have yellow or blue feathers, respectively; and budgies that produce neither pigment are white (albino). List the genotypes for green, yellow, blue, and albino budgiesProblem 5
In a type of parakeet known as a 'budgie,' feather color is controlled by two genes. A yellow pigment is synthesized under the control of a dominant allele Y. Budgies that are homozygous for the recessive y allele do not synthesize yellow pigment. At an independently assorting gene, the dominant allele B directs synthesis of a blue pigment. Recessive homozygotes with the bb genotype do not produce blue pigment. Budgies that produce both yellow and blue pigments have green feathers; those that produce only yellow pigment or only blue pigment have yellow or blue feathers, respectively; and budgies that produce neither pigment are white (albino). A cross is made between a pure-breeding green budgie and a pure-breeding albino budgie. What are the genotypes of the parent birds?Problem 5
In a type of parakeet known as a 'budgie,' feather color is controlled by two genes. A yellow pigment is synthesized under the control of a dominant allele Y. Budgies that are homozygous for the recessive y allele do not synthesize yellow pigment. At an independently assorting gene, the dominant allele B directs synthesis of a blue pigment. Recessive homozygotes with the bb genotype do not produce blue pigment. Budgies that produce both yellow and blue pigments have green feathers; those that produce only yellow pigment or only blue pigment have yellow or blue feathers, respectively; and budgies that produce neither pigment are white (albino). If F₁ males and females are mated, what phenotypes are expected in the F₂, and in what proportions?Problem 5
In a type of parakeet known as a 'budgie,' feather color is controlled by two genes. A yellow pigment is synthesized under the control of a dominant allele Y. Budgies that are homozygous for the recessive y allele do not synthesize yellow pigment. At an independently assorting gene, the dominant allele B directs synthesis of a blue pigment. Recessive homozygotes with the bb genotype do not produce blue pigment. Budgies that produce both yellow and blue pigments have green feathers; those that produce only yellow pigment or only blue pigment have yellow or blue feathers, respectively; and budgies that produce neither pigment are white (albino). The cross of a green budgie and a yellow budgie produces offspring that are 12 green, 4 blue, 13 yellow, and 3 albino. What are the genotypes of the parents?Problem 5
In tomato plants, purple leaf color is controlled by a dominant allele A, and green leaf by a recessive allele a. At another locus, hairy leaf H is dominant to hairless leaf h. The genes for leaf color and leaf texture are separated by 16 m.u. on chromosome 5. On chromosome 4, a gene controlling leaf shape has two alleles: a dominant allele C that produces cut-leaf shape and a recessive allele c that produces potato-shaped leaf.
The cross of a purple, hairy, cut plant heterozygous at each gene to a green, hairless, potato plant produces the following progeny:
Phenotype Frequency % _
Purple, hairy, cut 21
Purple, hairy, potato 21
Green, hairless, cut 21
Green, hairless, potato 21
Purple, hairless, cut 4
Purple, hairless, potato. 4
Green, hairy, cut 4
Green, hairy, potato. 4 _
100
Give the genotypes of parental and progeny plants in this experiment.
