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

1. Identify the chromosomes involved in the disorder, which in this case are chromosomes 5 and 12.
2. Understand that cri-du-chat syndrome is caused by a terminal deletion on chromosome 5, meaning a portion of the chromosome is missing.
3. Examine the karyotype results to determine the specific location and extent of the deletion on chromosome 5.
4. Diagram the pairing of the abnormal chromosome 5 with its normal homologous chromosome, showing the deletion on one of the chromosome 5s.
5. Consider any potential translocations or rearrangements involving chromosome 12, as indicated by the karyotype, and include these in the diagram if present.

Key Concepts

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 implications of the karyotype results and the potential genetic risks for the couple's future pregnancies.

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 inheritance patterns and potential recurrence risks in affected families.