6. Chromosomal Variation

Chromosomal Rearrangements: Deletions

Multiple Choice
An intragenic deletion is a deletion found where?
Multiple Choice
Deletions can cause what type of phenotype?
Multiple Choice
Which of the following genetic diseases is an example of a chromosomal deletion?
Open Question
Human late prophase karyotypes have about 2000 visible G bands. The human genome contains approximately 22,000 genes. Consider the region 5p1.5 through the end of the short arm of chromosome 5, which is identified on the late prophase chromosome in Figure 10.5, and assume the entire region is deleted. Approximately how many genes will be lost as a result of the deletion?
Open Question
From the following list, identify the types of chromosome changes you expect to show phenotypic consequences.

interstitial deletion
Open Question
From the following list, identify the types of chromosome changes you expect to show phenotypic consequences.terminal deletion
Open Question
The mutations called bobbed in Drosophila result from variable reductions (deletions) in the number of amplified genes coding for rRNA. Researchers trying to maintain bobbed stocks have often documented their tendency to revert to wild type in successive generations. Propose a mechanism based on meiotic recombination which could account for this reversion phenomenon. Why would wild-type flies become more prevalent in Drosophila cultures?
Open Question
A healthy couple with a history of three previous spontaneous abortions has just had a child with cri-du-chat syndrome, a disorder caused by a terminal deletion of chromosome 5. Their physician orders karyotype analysis of both parents and of the child. The karyotype results for chromosomes 5 and 12 are shown here.Do the karyotypes of the parents help explain the occurrence of the three previous spontaneous abortions? Explain.
Open Question
A healthy couple with a history of three previous spontaneous abortions has just had a child with cri-du-chat syndrome, a disorder caused by a terminal deletion of chromosome 5. Their physician orders karyotype analysis of both parents and of the child. The karyotype results for chromosomes 5 and 12 are shown here.What is the approximate probability that the next child of this couple will have cri-du-chat syndrome?
Open Question
A healthy couple with a history of three previous spontaneous abortions has just had a child with cri-du-chat syndrome, a disorder caused by a terminal deletion of chromosome 5. Their physician orders karyotype analysis of both parents and of the child. The karyotype results for chromosomes 5 and 12 are shown here.What segregation pattern occurred to produce the gamete involved in fertilization of the child with cri-du-chat syndrome?
Open Question
A healthy couple with a history of three previous spontaneous abortions has just had a child with cri-du-chat syndrome, a disorder caused by a terminal deletion of chromosome 5. Their physician orders karyotype analysis of both parents and of the child. The karyotype results for chromosomes 5 and 12 are shown here.Diagram the pairing of the abnormal chromosomes.
Open Question
A healthy couple with a history of three previous spontaneous abortions has just had a child with cri-du-chat syndrome, a disorder caused by a terminal deletion of chromosome 5. Their physician orders karyotype analysis of both parents and of the child. The karyotype results for chromosomes 5 and 12 are shown here.Why does this parent have a normal phenotype?
Open Question
A healthy couple with a history of three previous spontaneous abortions has just had a child with cri-du-chat syndrome, a disorder caused by a terminal deletion of chromosome 5. Their physician orders karyotype analysis of both parents and of the child. The karyotype results for chromosomes 5 and 12 are shown here.Which parent has an abnormal karyotype? How can you tell? What is the nature of the abnormality?
Open Question
A healthy couple with a history of three previous spontaneous abortions has just had a child with cri-du-chat syndrome, a disorder caused by a terminal deletion of chromosome 5. Their physician orders karyotype analysis of both parents and of the child. The karyotype results for chromosomes 5 and 12 are shown here.Are the chromosomes in the child consistent with those expected in a case of cri-du-chat syndrome? Explain your reasoning.