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Exam 8: Chromosome Variation

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Question 1

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

A) acrocentric
B) metacentric
C) paracentric
D) submetacentric
E) telocentric

F) D) and E)
G) A) and B)

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Question 2

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Which form of aneuploidy causes primary Down syndrome?

A) nullisomy
B) monosomy
C) disomy
D) trisomy
E) tetrasomy

F) All of the above
G) A) and B)

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Question 3

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

You are studying the inheritance of the autosomal recessive traits, curly wings (cy) and ebony body color (e), in Drosophila. The cy locus is on chromosome 2 and the e locus is on chromosome 3. In the course of this study, you identify a strain of flies that carries a translocation between chromosome 2 and chromosome 3. Neither cy nor e is located in the translocation region. You generate flies with the following genotype: N2(cy)/T2(cy+); N3(e)/T3(e+) [N2 indicates a normal chromosome 2; T2 indicates a translocation chromosome with the centromere of chromosome 2 and a portion of chromosome 3; cy is the mutant allele associated with the curly wing phenotype, cy+ is the wild-type allele.] These flies have normal wings and normal body color. a. Draw the pairing of these chromosomes during meiosis I. b. Indicate the gametes that would be generated by alternate and adjacent-1 segregation patterns during meiosis I. c. You mate two of these flies to one another. Indicate the expected genotypes and phenotypes (and their proportions) in the offspring.

You are studying the inheritance of the recessive red-spotted (r) trait in pea plants. You identify a phenotypically wild-type plant that, when crossed to a red-spotted plant, produces 5/6 wild-type offspring and 1/6 red-spotted offspring. When you look at the chromosomes of the wild-type plant, you note that it contains an extra copy of chromosome 2, which is where the red-spotted locus is located. a. What is the genotype of the wild-type plant? What gametes will this plant generate? What are the genotypes of the wild-type and red-spotted offspring? b. You identify a plant that you think is genotypically Rrr. If you cross this plant to an rr individual, what proportion of wild-type and red-spotted offspring would you expect?

The inheritance of both chromosomes from the same parent is a condition called:

Which of the following is represented in the figure?

What would be the consequence of a diploid gamete (resulting from meiotic nondisjunction) being fertilized by a haploid gamete from the same species?

Which of the following chromosome rearrangements represents duplication?

Describe two ways in which an inversion can alter gene expression.

The centromere is at or very near the end in which type of chromosome?

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 amphidiploid beetle produced from this cross?

_____ can cause genes to move from one linkage group to another.

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?

In order to perform karyotype analysis, chromosomes are obtained from actively dividing cells and treated with chemicals to keep them at the _____ stage of mitosis.

Which type of chromosome mutation increases the amount of genetic material for all chromosomes?

A man has a condition where all of his gametes undergo meiosis I normally, but there is nondisjunction of the sex chromosomes in 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 rearrangements represents inversion?

Duchenne muscular dystrophy (DMD) is normally an X-linked recessive human disease affecting boys. Girls afflicted with DMD are rare. Cytogenetic studies of several girls with DMD have in each case revealed that these individuals carry X-autosome translocations. The autosomes vary, but the breakpoint on the X in every case is in band p21, which is the location of the DMD gene. Cytogenetic studies further revealed that in all cells studied in such DMD girls the normal X chromosome exists as a Barr body. How might these observations account for the existence of DMD-affected girls? Why is only the normal X, but not the translocated X, inactivated?

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