Chapter 3 Answers

    1. Since chromosomes vary greatly in size, the number of chromosomes does not correlate with the total DNA content. For reasons discussed in Chapter 5 and this chapter, the number of genes does not correlate closely to DNA content either.
    2. Heterochromatic regions with repetitive DNA, centromeres, and telomeres are examples of gene-poor regions of chromosomes.
      1. Only one (except for holocentric chromosomes, not discussed in this chapter).
      2. The two centromeres might get pulled towards opposite poles at mitosis/meiosis resulting in chromosome breakage.
      3. It would not segregate properly at mitosis or meiosis, leading to aneuploidy. In order to segregate correctly, there would have to be another way to control its movement at mitosis and meiosis.
      1. At the end of G1, 16 chromosomes with 1 chromatid each.
      2. At the end of S, 16 chromosomes with 2 chromatids each.
      3. At the end of G2, 16 chromosomes with 2 chromatids each.
      4. At the end of mitosis, 16 chromosomes with 1 chromatid each.
      1. There is little correlation between any of these, with the exception that larger genomes tend to have more genes.
      2. The C-value paradox can be explained by genomes having different amounts of non-coding DNA between genes and within genes as introns.
      3. If we define “organismal complexity” as the size of the genome (or number of cells/organism), then larger, more complex organism tend to have more genes although not always and not in a direct, linear, proportioned manner. Also, those with larger genomes tend to have greater distances between genes.

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Introduction to Genetics Copyright © 2023 by Natasha Ramroop Singh, Thompson Rivers University is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

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