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CASE STUDY | Timing is everything
A man in his early 20s received chemotherapy and radiotherapy as treatment every 60 days for Hodgkin disease. After unsuccessful attempts to have children, he had his sperm examined at a fertility clinic, upon which multiple chromosomal irregularities were discovered. When examined within 5 days of a treatment, extra chromosomes were often present or one or more chromosomes were completely absent. However, such irregularities were not observed at day 38 or thereafter.
How might a geneticist explain the time-related differences in chromosomal irregularities?
Case summary:
A male, who suffers from Hodgkin disease receive chemotherapy and radiotherapy treatment every 60 days. His age is in the early 20s and his attempts to have children are unsuccessful. The reason is chromosomal irregularities, which is prominent when he is examined during the first 5 days of treatment.
Characters of the case:
A male patient.
Adequate information:
Hodgkin's disease is a type of cancer which affects lymphatic system and treatment includes radiotherapy and chemotherapy.
To determine:
The time-related chromosomal irregularities during chemotherapy and radiotherapy treatment in a patient suffering from Hodgkin disease.
Explanation of Solution
Given information:
The chromosomal irregularities are not found when examined on or after 38 days of treatment.
The sperm or gamete produced when the person is under treatment is infertile as chemotherapy and radiotherapy can affect healthy cells. The process of meiosis which produces four gametes (sperms) with a haploid number of chromosomes is affected because of high exposure to chemotherapeutic drugs and radiations given during treatment.
Meiosis is the cell division which takes place in germ-line cells which is a layer of undifferentiated cells called spermatogonium present in testes (male reproductive organ). Meiosis produces four haploid gametes or sperms from diploid germ cell which becomes primary spermatocyte to undergo first meiotic division. The product of this division is called secondary spermatocyte which undergoes a second meiotic division to produce spermatids. Spermiogenesis is a specialized process which gives rise to motile sperm with a haploid number of chromosomes.
Sperm produced during the first days of treatment have chromosomal irregularities which include the presence of extra chromosomes or absence of certain chromosomes as the dosage of chemotherapy and radiotherapy affects the germ-line cell division. But at day 38 or thereafter, the dosage level reduces which may not have a direct effect on germ-line cell division. Therefore, chromosomal irregularities are based on the level of exposure to the radiation and chemotherapeutic drugs.
Thus, it can be concluded that the chromosomal irregularities are high during the initial days of treatment as the exposure is high but the level of exposure reduces after 38 days.
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Chapter 2 Solutions
Essentials of Genetics (9th Edition) - Standalone book
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