Consider the imaginary linked genes A and B in Neurospora . The formula for calc
ID: 55241 • Letter: C
Question
Consider the imaginary linked genes A and B in Neurospora. The formula for calculating gene to gene distance for tetrad analysis is: RF = ([1/2TT] + NPD)/Total tetrads (if the data are in percent, there is no need for the denominator).
35% of meioses display no crossover.
35% have one crossover in the region between the genes.
30% have two crossovers in the region between the genes.
What is the predicted recombination frequency? Show your work, including the formula used to calculate the recombination frequency.
Which tetrad type numbers in the progeny should be compared to determine if genes in Neurospora are linked? Explain why.
Explanation / Answer
Ans. a.) Predicted recombination frequency is determined by the following formula -
Recombination frequency = Progeny showing recombinant phenotype / total progeny
As it is given that the
progenies show no cross over (no recombination) = 35/100
progenies have one cross over (a sign of recombination) = 35/100
progeny two cross overs (nullify the effect of each other so no recombination) = 30/100
Thus, the estimated recombination frequency would be 35%.
b.) When the number of offspring with parental genotype is higher than the other genotypic combinations, then the genes are linked. But when the number of parental type genotype is equal to the other combination it shows absence of linking. Hence in the mentioned situation no linked gene is found.