Textbook Question
In what way does position effect variegation (PEV) of Drosophila eye color indicate that chromatin state can affect gene transcription?
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Ch. 10 - Eukaryotic Chromosome Abnormalities and Molecular Organization
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172
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Table of contents
- Ch. 1 - The Molecular Basis of Heredity, Variation, and Evolution64
- Ch. 2 - Transmission Genetics144
- Ch. 3 - Cell Division and Chromosome Heredity81
- Ch. 4 - Gene Interaction87
- Ch. 5 - Genetic Linkage and Mapping in Eukaryotes103
- Ch. 6 - Genetic Analysis and Mapping in Bacteria and Bacteriophages73
- Ch. 7 - DNA Structure and Replication71
- Ch. 8 - Molecular Biology of Transcription and RNA Processing79
- Ch. 9 - The Molecular Biology of Translation110
- Ch. 10 - Eukaryotic Chromosome Abnormalities and Molecular Organization100
- Ch. 11 - Gene Mutation, DNA Repair, and Homologous Recombination86
- Ch. 12 - Regulation of Gene Expression in Bacteria and Bacteriophage90
- Ch. 13 - Regulation of Gene Expression in Eukaryotes38
- Ch. 14 - Analysis of Gene Function via Forward Genetics and Reverse Genetics72
- Ch. 15 - Recombinant DNA Technology and Its Applications69
- Ch. 16 - Genomics: Genetics from a Whole-Genome Perspective49
- Ch. 17 - Organelle Inheritance and the Evolution of Organelle Genomes27
- Ch. 18 - Developmental Genetics43
- Ch. 19 - Genetic Analysis of Quantitative Traits66
- Ch. 20 - Population Genetics and Evolution at the Population, Species, and Molecular Levels105
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook
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Sanders 3rd EditionCh. 10 - Eukaryotic Chromosome Abnormalities and Molecular OrganizationProblem 12c
Sanders 3rd EditionCh. 10 - Eukaryotic Chromosome Abnormalities and Molecular OrganizationProblem 12cChapter 10, Problem 12c
A pair of homologous chromosomes in Drosophila has the following content (single letters represent genes):
Chromosome 1RNMDHBGKWU
Chromosome 2RNMDHBDHBGKWU
What term best describes the unusual structure that forms during pairing of these chromosomes?
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Identify the gene sequences on both homologous chromosomes: Chromosome 1 has the sequence RNMDHBGKWU, and Chromosome 2 has the sequence RNMDHBDHBGKWU.
Compare the sequences of the two chromosomes to identify any differences. Notice that Chromosome 2 has an extra segment 'DHBG' inserted between 'D' and 'K'.
Understand that during meiosis, homologous chromosomes pair up and align gene by gene. However, the extra segment in Chromosome 2 will cause misalignment.
Recognize that this misalignment leads to the formation of a loop structure in the chromosome with the extra segment (Chromosome 2) to accommodate the additional genetic material.
Conclude that the term describing this unusual structure is a 'deletion loop' or 'insertion loop,' depending on the perspective, as it forms due to the presence of an extra segment in one homologous chromosome.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Homologous Chromosomes
Homologous chromosomes are pairs of chromosomes in a diploid organism that have the same structure and gene sequence but may contain different alleles. In Drosophila, like in other organisms, these chromosomes pair during meiosis, allowing for genetic recombination and ensuring that each gamete receives one chromosome from each pair.
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Chromosome Structure
Chromosomal Pairing
Chromosomal pairing occurs during meiosis when homologous chromosomes align closely along their lengths. This process is crucial for the exchange of genetic material through crossing over, which increases genetic diversity. The unusual structure that forms during this pairing can lead to unique configurations, especially when there are differences in gene content or structure.
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Synapsis
Synapsis is the process during prophase I of meiosis where homologous chromosomes become closely associated, forming a structure known as a synaptonemal complex. This complex facilitates the exchange of genetic material between chromatids, which is essential for proper segregation of chromosomes and genetic variation in offspring.
Related Practice
Textbook Question
A pair of homologous chromosomes in Drosophila has the following content (single letters represent genes):
Chromosome 1RNMDHBGKWU
Chromosome 2RNMDHBDHBGKWU
What term best describes this situation?
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Textbook Question
A pair of homologous chromosomes in Drosophila has the following content (single letters represent genes):
Chromosome 1RNMDHBGKWU
Chromosome 2RNMDHBDHBGKWU
Diagram the pairing of these homologous chromosomes in prophase I.
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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?
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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.
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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?
518
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