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Exam 6: Chromosome Variation

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Question 21

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A plant species has 2n = 18 chromosomes.How many chromosomes would you expect to find in a tetrasomic individual of this species?

A) 17
B) 19
C) 20
D) 22
E) 36

F) A) and C)
G) A) and E)

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Question 22

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A newly discovered species of dung beetle has 2n = 16 chromosomes.It mates with a closely related beetle species that has 2n = 12 chromosomes.How many chromosomes would there be in an allotriploid beetle produced from this cross?

A) 13 or 17
B) 19 or 25
C) 18 or 24
D) 20 or 22
E) 36 or 48

F) C) and E)
G) B) and E)

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Question 23

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Which of the following is a form of aneuploidy in which two members of the same homologous pair are absent?

A man has a condition where all of his gametes undergo nondisjunction of the sex chromosomes in meiosis I, but meiosis II proceeds normally.He mates with a woman who produces all normal gametes.What is the probability that the fertilized egg will develop into a child with Turner syndrome (XO) ? Assume that all gametes and zygotes are viable.

Which of the following is NOT a rearrangement that causes chromosomal mutations?

Which of the following is a form of aneuploidy in which four members of the same homologous pair are present?

Approximately _____ of the gametes produced by an individual heterozygous for a translocation will be nonviable.

Which form of aneuploidy describes an organism that is missing a single chromosome?

Which type of chromosome has the centromere located approximately in the middle?

Down syndrome has, in some cases, been found to run in families.Explain the genetic basis for this inherited form of the condition.

Wild-type Arabidopsis has five chromosomes (2n = 10) .Trisomic plants are designated as Tr followed by the trisomic chromosome number-that is, Tr1 is trisomic for chromosome 1.Assuming that trisomy is fully viable and that all possible pairing configurations (including nonpairing) are possible at meiosis, what proportion of the progeny from the cross wt × Tr1 will have a wild-type chromosomal complement?

Most strains of cultivated bananas were created by crossing plants within and between two diploid species: Musa acuminata (genome = AA) and Musa balbisiana (genome = BB) .Bananas with a genome of AAB are an example of which kind of polyploidy?

A woman has a condition where all of her gametes undergo nondisjunction of chromosome 21 in meiosis I, but meiosis II proceeds normally.She mates with a man who produces all normal gametes.What is the probability that the fertilized egg will develop into a child with Down syndrome? Assume that all gametes and zygotes are viable.

Which type of chromosome mutation can DECREASE the amount of genetic material for one entire chromosome?

Which form of aneuploidy causes primary Down syndrome?

A man has a condition where all of his gametes undergo meiosis I normally, but there is nondisjunction of the sex chromosomes in every meiosis II.He mates with a woman who produces all normal gametes.What is the probability that the fertilized egg will develop into a child with Klinefelter syndrome (XXY) ? Assume that all gametes and zygotes are viable.

Which of the following chromosome mutations would NOT cause loops to form during chromosome pairing in prophase I of meiosis?

Which type of chromosome has a centromere displaced toward one end, creating a long arm and a short arm?

Isochromosomes have the structure ABC^-CBA (where ^- represents the centromere, and A, B, and C represent wild-type alleles of three different genes).In some cases, such isochromosomes are derived from two copies of one-half of a metacentric chromosome, which has a centromere near its center.For example, a wild-type metacentric chromosome ABC^-DEF might form two distinct isochromosomes, ABC-CBA and FED-DEF.The centromeres of such distinct isochromosomes can be homologous, so that they cause the segregation of the two distinct isochromosomes from each other during meiosis. a.A mutant of genotype ABC-CBA/FED-DEF is viable.If you cross this mutant with a wild-type individual, what would you expect to be the genotype of the offspring? Would these offspring be viable or not? Explain. b.What would you expect if you cross this mutant with another individual of genotype ABC-CBA/FED-DEF? Explain. c.You are given a pericentric inversion mutant in which this same chromosome is of genotype ABD-CEF.In an individual heterozygous for this inversion and a wild-type chromosome there is a crossover between C and the centromere, as follows: Indicate the gametes that would be generated. d.Assume that the inversion interval is very small, so that both duplications and deletions for this interval (from C to

Wild-type Arabidopsis has five chromosomes (2n = 10) .Trisomic plants are designated as Tr followed by the trisomic chromosome number-that is, Tr1 is trisomic for chromosome 1.Assuming that trisomy is fully viable and that all possible pairing configurations (including nonpairing) are possible at meiosis, what proportion of the progeny from the cross Tr1 × Tr1 will have a wild-type chromosomal complement?