Concept explainers
In Neurospora, his2 mutants require the amino acid histidine for growth, and lys4 mutants require the amino acid lysine. The two genes are on the same arm of the same chromosome, in the order
centromere - his2 - lys4.
A his2 mutant is mated with a lys4 mutant. Draw all of the possible ordered asci that could result from meioses in which the following events occurred, accounting for the nutritional requirements for each ascospore. Ascospores without any copy of a chromosome will abort and die, turning white in the process.
a. | A single crossover between the centromere and his2 |
b. | A single crossover between his2 and lys4 |
c. | Nondisjunction during the first meiotic division |
d. | Nondisjunction during the second meiotic division |
e. | A single crossover between the centromere and his2, followed by nondisjunction during the first meiotic division |
f. | A single crossover between his2 and lys4, followed by nondisjunction during the first meiotic division |
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Chapter 13 Solutions
ND STONY BROOK UNIVERSITY LOOSELEAF GENETICS: FROM GENES TO GENOMES
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Biology Illinois Edition (Glencoe Science)
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