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Unformatted text preview: and H4.
Yeast mitotic chromosomes are not visible microscopically in the same way human chromosomes are visible in
karyotype analysis. Pulse-ﬁeld gel electrophoresis, which
separates intact yeast chromosomes using alternating
pulses of current, produces molecular “karyotypes” of the
yeast genome, such as the one shown in Fig. A.3b. Geneticists use these karyotypes to conﬁrm the number of yeast
chromosomes and to observe major alterations in chromosome structure. As Figure A.3b indicates, chromosome I,
about 235 kb in length, is the smallest yeast chromosome.
Chromosome XII is the largest; its size varies between
about 2060 and 3060 kb because of a variable number of tandem ribosomal RNA genes (rDNA)—usually in the
range of 100–200 copies—in different strains. Genetic Maps and Recombination Frequencies
The classical genetic map of yeast currently shows the
locations of over 1000 markers determined by tetrad
analysis (see Chapter 3 of the main textbook). The total
genetic map length, a function of the frequency of meiotic recomb...
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- Spring '08