Table of contents

1. Introduction to Genetics51m
2. Mendel's Laws of Inheritance3h 37m
3. Extensions to Mendelian Inheritance2h 41m
4. Genetic Mapping and Linkage2h 28m
5. Genetics of Bacteria and Viruses1h 21m
6. Chromosomal Variation1h 48m
7. DNA and Chromosome Structure56m
8. DNA Replication1h 10m
9. Mitosis and Meiosis1h 34m
10. Transcription1h 0m
11. Translation58m
12. Gene Regulation in Prokaryotes1h 19m
13. Gene Regulation in Eukaryotes44m
14. Genetic Control of Development44m
15. Genomes and Genomics1h 50m
16. Transposable Elements47m
17. Mutation, Repair, and Recombination1h 6m
18. Molecular Genetic Tools19m
- Genetic Cloning
  9m
- Methods for Analyzing DNA
  9m
19. Cancer Genetics29m
- Overview of Cancer
  21m
- Cancer Mutations
  7m
20. Quantitative Genetics1h 26m
21. Population Genetics50m
- Hardy Weinberg
  19m
- Allelic Frequency Changes
  31m
22. Evolutionary Genetics29m

6. Chromosomal Variation

Chromosomal Rearrangements: Deletions

Genetics

6. Chromosomal Variation

Chromosomal Rearrangements: Deletions

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2:11 minutes

Problem 32d

Textbook 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.

Verified step by step guidance

Step 1: Understand the genetic basis of cri-du-chat syndrome. This disorder is caused by a terminal deletion on the short arm of chromosome 5 (5p). The deletion results in the loss of genetic material, leading to the characteristic symptoms of the syndrome.

Step 2: Review the karyotype analysis results for the parents and the child. Focus on identifying any structural abnormalities in chromosomes 5 and 12, such as deletions, translocations, or other rearrangements.

Step 3: Diagram the pairing of the abnormal chromosomes during meiosis. To do this, illustrate how the deleted chromosome 5 from the child aligns with the normal chromosome 5 from the parent. Use a visual representation to show the missing segment on chromosome 5p.

Step 4: Consider the possibility of a balanced translocation in one of the parents. If one parent has a balanced translocation involving chromosomes 5 and 12, this could explain the inheritance pattern and the occurrence of cri-du-chat syndrome in the child. Diagram how the translocated chromosome pairs with its homologous chromosome during meiosis.

Step 5: Label the diagram clearly to indicate the normal and abnormal chromosomes, the deleted region on chromosome 5, and any translocations involving chromosome 12. This will help visualize the genetic mechanism leading to the disorder.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Karyotype Analysis

Karyotype analysis is a laboratory technique that involves the examination of an individual's chromosomes to identify genetic abnormalities. It provides a visual representation of the number and structure of chromosomes, allowing for the detection of deletions, duplications, or other chromosomal rearrangements. In this case, it is crucial for understanding the chromosomal basis of cri-du-chat syndrome and assessing the genetic status of the parents.

Cri-du-chat Syndrome

Cri-du-chat syndrome is a genetic disorder caused by a deletion of a portion of chromosome 5, specifically at the 5p15.2 region. This condition is characterized by distinctive features such as a high-pitched cry resembling that of a cat, developmental delays, and various physical anomalies. Understanding this syndrome is essential for interpreting the karyotype results and the implications for the family.

Chromosomal Deletion

A chromosomal deletion occurs when a segment of a chromosome is missing or deleted, which can lead to genetic disorders due to the loss of essential genes. In cri-du-chat syndrome, the deletion affects critical genes on chromosome 5, resulting in the symptoms associated with the disorder. Recognizing the nature of chromosomal deletions is vital for understanding the genetic risks and potential outcomes for the couple's future pregnancies.

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Textbook 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?

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Textbook 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.

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views

Textbook 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?

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Textbook 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?

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?

332

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Textbook 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.

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Multiple Choice

An intragenic deletion is a deletion found where?

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