In a reciprocal translocation, two chromosomes exchange parts without losing genetic material, which can lead to the formation of gametes with various combinations of chromosomes due to the way these chromosomes segregate during meiosis.
For the man with a reciprocal translocation between chromosomes 4 and 12, let’s consider how his sperm cells might form during meiosis:
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Normal Pairing: Normally, during meiosis, each chromosome pairs with its homologous chromosome. However, with the translocation, the pairing can lead to different configurations.
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Possible Chromosome Configurations: The man can pass on:
- Both normal chromosome 4 and chromosome 12.
- The translocated version of chromosome 4 (which is part translocated with chromosome 12) and the translocated version of chromosome 12 (which is part translocated with chromosome 4).
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The possible gametes that might be formed can be summarized as:
- Normal gamete (normal chromosome 4 and normal chromosome 12)
- Gamete with translocated chromosome 4 (which is part of chromosome 12)
- Gamete with translocated chromosome 12 (which is part of chromosome 4)
In a typical meiotic process for a reciprocal translocation involving two chromosomes, the gametes can produce four combinations (based on how the chromosomes segregate). The possible outcomes based on the presence of the reciprocal translocation can be simplified into:
- 1/4 of the gametes will be normal (normal chromosome 4 and normal chromosome 12).
- 3/4 of the gametes will have at least one chromosome with a translocation.
Thus, the correct outcome for the probability that his sperm cells will carry at least one chromosome with a translocation is: Three-fourths will have at least one chromosome with a translocation; the other 1/4 will carry normal chromosomes 4 and 12.