result of a meiotic event in occurred? ssover(s) most likely occur? were involve

Question

result of a meiotic event in occurred? ssover(s) most likely occur? were involved, were they two- trand multiple crossovers? 29.) From a cross of a wild-type Neurospora strain with a strain that has nutritional requirements for the amino acids histidine (bis) and tyrosine (yr), the following ordered tetrads were obtained (a) What is the map distance between the bis locus and the cen- tromerer (b) What is the linkage relationship between the bis and tyr loci? Spore Pairs Tetrads 4 + tyr+ tyr bis + + tyr his+his tyr bis tyr +t + tyr tyr bisbis tyr bis tyr bis ty bis tyr bist bis++ bis tyr bis tyr 1-2 3-4 5-6 7-8 his+ ++ bis++ tyr t +t bis + Number 30 30 10 Total = 100

Explanation / Answer

(a) Column 1 and column 4 are non recombinants(30+30=60)

Recombinants are in rest of the other columns.(8+5+10+7+8+2=40)

Recombination frequency= (total recombinants /total progeny)*100 = (40/100)*100 =40%

Distance between the gene and the centromere has to be made into half (40/2=20 map units)

so 20 map units is the distance between the gene and the centromere

(b) First column shows parental ditype (PD) = 30

fourth column shows non parental ditype (NPD)=30

PD=NPD , so genes are not linked

therefore there is no linkage relationship between the genes.

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