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?

Verified step by step guidance

1. Identify the genetic disorder: Cri-du-chat syndrome is caused by a deletion on chromosome 5.
2. Review the karyotype results: Compare the karyotypes of both parents and the child, focusing on chromosome 5.
3. Look for deletions: Check if either parent has a deletion on chromosome 5 similar to the child’s deletion.
4. Consider balanced translocations: If no deletion is found, examine if one parent has a balanced translocation involving chromosome 5 and another chromosome, such as chromosome 12.
5. Determine the abnormality: Conclude which parent has the abnormal karyotype based on the presence of a deletion or a balanced translocation that could lead to the child’s condition.

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 structural changes. In this case, analyzing the karyotypes of the parents and child will help determine if there are any chromosomal abnormalities linked to the child's cri-du-chat syndrome.

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, including a high-pitched cry resembling a cat, developmental delays, and various physical anomalies. Understanding this syndrome is crucial for interpreting the karyotype results and assessing the potential genetic contributions from the parents.

Chromosomal Abnormalities

Chromosomal abnormalities can occur in various forms, including deletions, duplications, inversions, and translocations. In the context of this question, a terminal deletion of chromosome 5 is responsible for the child's cri-du-chat syndrome. Identifying which parent has an abnormal karyotype will involve comparing the karyotype results to determine if one parent carries a similar deletion or other chromosomal irregularities that could explain the child's condition.