Textbook Question
From the following list, identify the types of chromosome changes you expect to show phenotypic consequences.
Reciprocal balanced translocation
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6. Chromosomal Variation
Chromosomal Rearrangements: Translocations
2:04 minutesProblem 13b
Textbook Question
An animal heterozygous for a reciprocal balanced translocation has the following chromosomes:
MN • OPQRST
MN • OPQRjkl
cdef • ghijkl
cdef • ghiST
Identify the gametes produced by alternate segregation. Which, if any, of these gametes are viable?
Verified step by step guidance1
Step 1: Understand the concept of reciprocal balanced translocation. This occurs when two non-homologous chromosomes exchange segments without any genetic material being lost or gained. In a heterozygous individual, one set of chromosomes is normal, and the other set carries the translocation.
Step 2: Recognize alternate segregation. During meiosis, alternate segregation refers to the separation of chromosomes such that the translocated chromosomes move to one pole and the normal chromosomes move to the opposite pole. This results in gametes that either contain both translocated chromosomes or both normal chromosomes.
Step 3: Analyze the chromosome combinations resulting from alternate segregation. The gametes produced will be: (1) MN • OPQRST and cdef • ghiST (normal chromosomes), and (2) MN • OPQRjkl and cdef • ghijkl (translocated chromosomes).
Step 4: Determine viability of the gametes. Gametes are viable if they contain a balanced set of genetic material. Both combinations from alternate segregation are balanced because they either contain the normal chromosomes or the translocated chromosomes, ensuring no genetic material is missing or duplicated.
Step 5: Conclude that the gametes produced by alternate segregation are viable. This is because the genetic material is balanced in both cases, allowing for proper development if fertilization occurs.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Reciprocal Balanced Translocation
A reciprocal balanced translocation occurs when two non-homologous chromosomes exchange segments without any loss of genetic material. This results in a rearrangement of genetic information but maintains the overall balance of genes. In heterozygous individuals, one chromosome carries the normal arrangement while the other has the translocated segments, which can affect gamete formation and viability.
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Segregation Patterns in Meiosis
During meiosis, chromosomes segregate into gametes, and the pattern of segregation can influence genetic diversity. In the case of reciprocal translocations, alternate segregation leads to gametes that contain either all normal chromosomes or all translocated chromosomes. Understanding these patterns is crucial for predicting the viability of the resulting gametes.
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Viability of Gametes
The viability of gametes refers to their ability to develop into a viable organism upon fertilization. In the context of reciprocal balanced translocations, gametes produced by alternate segregation are typically viable because they maintain a complete set of genetic information. However, those produced by adjacent segregation may be unbalanced and often lead to non-viable offspring.
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