From a cross between e+ f+ g+ and e− f − g− strains ofNeurospora, recombination between these linkedgenes resulted in a few octads containing the followingordered set of spores:e+ f+ g+e+ f+ g+e+ f − g+e+ f − g+e− f − g−e− f − g−e− f − g−e− f − g−a. Where was recombination initiated?b. Did crossing-over occur between genes e and g?Explain.c. Why do you end up with 2 f+ : 6 f − but 4 e+: 4 e−and 4g+: 4g−?d. Could you characterize these unusual octads as MIor MII for any of the three genes involved?Explain.
Genetic Recombination
Recombination is crucial to this process because it allows genes to be reassorted into diverse combinations. Genetic recombination is the process of combining genetic components from two different origins into a single unit. In prokaryotes, genetic recombination takes place by the unilateral transfer of deoxyribonucleic acid. It includes transduction, transformation, and conjugation. The genetic exchange occurring between homologous deoxyribonucleic acid sequences (DNA) from two different sources is termed general recombination. For this to happen, an identical sequence of the two recombining molecules is required. The process of genetic exchange which occurs in eukaryotes during sexual reproduction such as meiosis is an example of this type of genetic recombination.
Microbial Genetics
Genes are the functional units of heredity. They transfer characteristic information from parents to the offspring.
From a cross between e+ f
+ g+ and e− f − g− strains of
Neurospora, recombination between these linked
genes resulted in a few octads containing the following
ordered set of spores:
e+ f
+ g+
e+ f
+ g+
e+ f − g+
e+ f − g+
e− f − g−
e− f − g−
e− f − g−
e− f − g−
a. Where was recombination initiated?
b. Did crossing-over occur between genes e and g?
Explain.
c. Why do you end up with 2 f
+ : 6 f − but 4 e+: 4 e−
and 4g+: 4g−?
d. Could you characterize these unusual octads as MI
or MII for any of the three genes involved?
Explain.
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