Using only two genes at a time in recombination mapping, the maximum map distanc

Question

Using only two genes at a time in recombination mapping, the maximum map distance that can be calculated is 50 map units. This is because There are as many even-numbered double crossovers as there are odd double crossovers at 50 map units or greater There is no way to collect enough data to accurately map distances beyond 50 map units No chromosome is more than 50 map units long If you map more than 50 map units you are studying genes on different chromosomes Genes at 50 map units lie directly adjacent to each other so that there are not any more crossovers between the genes A recombination map does not directly reflect the physical map. Why? Some areas of a chromosome have more crossovers than others There is never enough data to be that accurate You always miss double crossovers, but if you found all of them the two maps would be identical Any crossover distorts the recombination map None of the above is true. A good recombination map will be exactly what a good physical map will be In haploid fungi, which of the following is used to calculate the distance between the centimeter and the gene of interest? The percentage of individuals experiencing double-crossover events The number of diploid

Explanation / Answer

1.

The correct answer is option (D) if you map more than 50 map units you are studying genes on different chromosomes.

Because of the way the calculations are performed, we can never have more than 50 map units. If two genes are greater than 50 cM apart, then we cannot determine if they reside on the same chromosome or are on different chromosomes.

2.

The right answer is option (A) some areas of a chromosome have more crossovers than others.

A recombination map shows the position of its known genes relative to each other in terms of recombination frequency, but not based on specific physical distance along each chromosome. Therefore, a genetic map can never be a physical map.

3.

The correct answer is option (D) the spores that have undergone second-division segregation.

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