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Ch. 10 - Eukaryotic Chromosome Abnormalities and Molecular Organization
Sanders - Genetic Analysis: An Integrated Approach 3rd Edition
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook
All textbooksSanders 3rd EditionCh. 10 - Eukaryotic Chromosome Abnormalities and Molecular OrganizationProblem 13c
Chapter 10, Problem 13c

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 adjacent-1 segregation. Which, if any, of these gametes are viable?

Verified step by step guidance
1
Understand the problem: The animal is heterozygous for a reciprocal balanced translocation, meaning two non-homologous chromosomes have exchanged segments. The chromosomes involved are MN • OPQRST, MN • OPQRjkl, cdef • ghijkl, and cdef • ghiST. The task is to identify the gametes produced by adjacent-1 segregation and determine their viability.
Recall the concept of adjacent-1 segregation: In adjacent-1 segregation, homologous centromeres segregate to opposite poles during meiosis. This results in gametes that contain one chromosome from each translocation pair, but these chromosomes are not complementary. This often leads to unbalanced gametes.
Determine the gametes produced: To identify the gametes, pair the chromosomes such that homologous centromeres segregate to opposite poles. For example, one gamete might contain MN • OPQRST and cdef • ghiST, while another might contain MN • OPQRjkl and cdef • ghijkl. Repeat this process to identify all possible combinations.
Assess the viability of the gametes: Viability depends on whether the gametes are balanced or unbalanced. Balanced gametes contain a complete set of genetic information, while unbalanced gametes have duplications or deletions of genetic material. Analyze each gamete to determine if it has duplications or deletions by comparing the segments present in each chromosome.
Conclude the analysis: Summarize which gametes are produced by adjacent-1 segregation and indicate their viability based on the presence or absence of genetic imbalances. Balanced gametes are typically viable, while unbalanced gametes are usually inviable due to missing or extra genetic material.

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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 chromosomes exchange segments without any loss of genetic material. This results in a rearrangement of genes but maintains the overall genetic balance. In organisms with such translocations, the chromosomes can pair during meiosis, leading to unique segregation patterns that can affect gamete viability.
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Reciprocal Translocation

Adjacent-1 Segregation

Adjacent-1 segregation is a specific way chromosomes can segregate during meiosis in individuals with reciprocal translocations. In this process, one chromosome from each pair of homologous chromosomes is selected, leading to gametes that contain both segments from one translocated chromosome and none from the other. This often results in gametes that are unbalanced and typically non-viable.
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Reciprocal Translocation

Gamete Viability

Gamete viability refers to the ability of gametes to develop into a viable organism after fertilization. In the context of adjacent-1 segregation, the resulting gametes may have an unbalanced set of chromosomes, which often leads to developmental issues or lethality. Understanding which gametes are viable is crucial for predicting the outcomes of genetic crosses involving translocations.
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Gamete Development
Related Practice
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?

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 adjacent-2 segregation. Which if any of these gametes are viable?

Textbook Question

An animal heterozygous for a reciprocal balanced translocation has the following chromosomes:

      MN • OPQRST

      MN • OPQRjkl

      cdef • ghijkl

      cdef • ghiST

Diagram the pairing of these chromosomes in prophase I.

Textbook Question

An animal heterozygous for a reciprocal balanced translocation has the following chromosomes:

MN • OPQRST           

MN • OPQRjkl           

cdef • ghijkl           

cdef • ghiST

Among the three segregation patterns, which is least likely to occur? Why?

Textbook Question

Dr. Ara B. Dopsis has an idea he thinks will be a boon to agriculture. He wants to create the 'pomato,' a hybrid between a tomato (Lycopersicon esculentum) that has 12 chromosomes and a potato (Solanum tuberosum) that has 48 chromosomes. Dr. Dopsis is hoping his new pomato will have tuber growth like a potato and the fruit production of a tomato. He joins a haploid gamete from each species to form a hybrid and then induces doubling of chromosome number. How many chromosomes will the hybrid have before chromosome doubling?

Textbook Question

A pair of homologous chromosomes in Drosophila has the following content (single letters represent genes):

Chromosome 1RNMDHBGKWU

Chromosome 2RNMDHBDHBGKWU

How does the pairing diagrammed in part (b) differ from the pairing of chromosomes in an inversion heterozygote?