In a transduction system using P1 page, the donor is pur + pro + his - and the r
ID: 58010 • Letter: I
Question
In a transduction system using P1 page, the donor is pur+ pro+ his- and the recipient is pur- pro- his+. The donor allele pur+ is initially selected after transduction, and 50 pur+ transductants are then scored for the other alleles present. Here are the results:
Genotype
# colonies
pro+ his+
4
pro+ his-
9
pro- his+
24
pro- his-
13
total
50
a) What is the cotransduction frequency for pur and pro?
b) What is the cotransduction frequency for pur and his?
c)Which of the unselected loci is closest to pur?
d)Are pro and his on the same side or opposite sides of pur? Please Explain.
Genotype
# colonies
pro+ his+
4
pro+ his-
9
pro- his+
24
pro- his-
13
total
50
Explanation / Answer
The maximum no. of genotypes is of pro-his+(=24), which is the parental type. This means pur+ has transferred first, making the genotype pur+pro-his+
The second number pro-his- (= 13), means his- is transferred next. so his is closest to pur.
a) What is the cotransduction frequency for pur and pro? = 4+9/50 *100= 26%
b) What is the cotransduction frequency for pur and his?=4+24/50 *100= 56%. This also shows that pur and his go together and are closer to each other.
c)Which of the unselected loci is closest to pur? his
d)Are pro and his on the same side or opposite sides of pur? same side
The position of genes should be pur--his--pro+ in the donor.
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