Please explain how to arrive at the correct answers and show calculations for pr
ID: 42359 • Letter: P
Question
Please explain how to arrive at the correct answers and show calculations for problems 11 and 12.
The gel on the left represents genomic DNA from three different animals that have been cut with the restriction enzyme Hindlll and run in three adjacent lanes on an electrophoretic gel. The extreme right lane contains DNA fragments of a specific size to serve as reference markers (kb = 1000 base pairs). This gel was subjected to Southern blot analysis using a radioactive probe that encoded a muscle-specific actin gene, and the autoradiograph on the right represents the results of that experiment. If the numbers on the above figure represent the Hindlll sites that surround the actin gene in this genome, which of the following would represent sites that showed polymorphism in these three individuals? 1 and 2; 1 and 3; 2 and 3; 3 and 4; 1 and 4. The distance between site 1 and site 4 in the genome is best estimated to be: 10 base pairs; 400 base pairs; 2000 base pairs 20,000 base pairs; 4 Times 105 base pairs.Explanation / Answer
11. c. 2 and 3
Gene monomorphism is represented by presence of same band in all the individuals at same position tested whereas polymorphisms are represented by alteration in the pattern of bands in different individuals indicating difference in their nucleotide sequence.
According to the position of restriction sites present in actin gene 3 restriction fragments (Fragment 1- from 1 to 2, Fragment 2- from 2 to 3 and Fragment 3- from 3 to 4) would be generated when digested with Hind III.
On analysing the pattern of bands obtained on Southern blotting we can note that there exists monomorphism for restriction fragment 1 and 4 (below 4.3 kb and at 9.4 kb, present in all the individuals at same position). If polymorphism existed between site 1 and 2 the number of restriction fragment generated would be less or if polymorphism existed between site 1 and 3 or 1 and 4 the number of restriction fragment generated would be more than expected. There is no polymorphism between 3 and 4 as there is monomorphic band observed at 9.4 kb corresponding to highest number of base pairs (possible only between 3 and 4 sites). Polymorphism is observed for fragment 2 (At 40.3 Kb for individual 1 and 2 from left whereas it is present at 6.7 kb for individual 3). This indicates that the three individual