Introduction to Chromosomes

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Introduction to Chromosomes
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a.
b.
e.
Eukaryotic Chromosomes a.
Drosophila polytene chromosomes. An Introduction
to Genetic Analysis, Griffiths et al., Fig. 8-4.
b. Mouse mitotic chromosomes, Genetics, Hartwell
et al., Chapter 12 front piece. c. Amphibian
lampbrush chromosomes. Molecular Biology of the
Cell, Alberts et al., Fig. 8-16. d. Human
mitotic chromosomes (prophase), P. Lichter et
al., 1990, Science 24764. e. Human mitotic
chromosomes (metaphase, disrupted). Epstein,
unpublished data.
d.
c.
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Haploid Chromosome Number (n) The number of
different chromosomes in most cells of the
organism. The haploid number is constant within a
species, but varies greatly between species. In
humans, n 23.
Genome The total DNA content (quantity and
quality) of the entire haploid chromosome set of
an organism. Diploid (2n) Most higher
organisms have two versions of each of their
chromosomes in most of their cells. Humans are
diploid. That means we have 2n, or 2 x 23 46
chromosomes in each of our cells. (We got one
haploid set from our mother, and the other
haploid set from our father.)