Question

A transformation experiment is performed with a donor strain of M. falcieri that is resistant to four drugs: A, B, C, and D. The recipient is sensitive to all four drugs. The transformed recipient cells are split in aliquots and plated on media containing various combinations of the drugs. The results are below. All drugs are added at the same time.

Drug(s) added	# of colonies	Drug(s) added	# of colonies
None	10,000	BC	50
A	1156	BD	48
B	1148	CD	784
C	1137	ABC	32
D	1161	ABD	42
AB	45	ACD	625
AC	641	BCD	34
AD	945	ABCD	25

1. 1. Three of the genes are closer together to each other (more tightly linked) than they are to the fourth gene. Which is that fourth, distant gene? How do you know this?   
2. 2. What is the order of the three linked genes? Draw the map, including the distances between the genes.

Answer 1

druy whole Recipient cell in sensitive to donor coll is resistant to all bransformed colle are those resistance gene from donor. all A, B, C and D four drugs. which recieve these doug 1 Drug (3) added No. of colonies 1156) 1148 1137 (1161 45 AC (641 AD 945 ABC ABD AD gcТ Hg c 1 a From this given table this given table it to can be observed that :- maximum no. of colonies are found to be drug pusistent D, colories are resistant to A and c. D > A >83c.. 1161 > 1156 > 11487 1137 . . After w in combination of Ази, AD Also gives AB gives araximum then comes very less no. of colonies AC AB gives very . in combination companion to Ac and no. of 3 druge, ACD gives maximum.

As we know that to go together. table that B linked genes have greater Thus, it is very clear from gene is distant gene. probability given a looking at no. of This can also be beoved colonies in ACO and - ACD gives 625 colonies means most of this gene is distant by ABCD. but colonies and not ACD with B gives only as are B sensitive because toans formed yet. ☺ Therefore B gene is distant gene. the gene, triple we must compare transformants. To calculate the order of ferequency of double and The frequency of AC This means I gene is and ACD present in difference. has no much middle . • Frequency gene is of AD close is to higher than D and than AC to that means A c). requency This of CD = 784 is tells that c is higher than close to AC= 641. than to A. Thus, order of gene must be CDA or ADC. More the frequency of co-transformation more will the linkage between genes. That means genes will be more close on chr. Co-transformation frequency of AD = 945 x 100 = 9.45% 10000 Co-transformation frequency of cD = 184 Kloo = 7,84 % Co- transformation free of Ac = bel xloo 2) 641%.