Human and Eukaryotic Genetics
Prob Set 7 due Tues, Nov 15
1. You have recently isolated five new phage that contain DNA from a human genomic DNA
library. You isolated these phage using a probe containing DNA from a region of
chromosome #2, where your favorite gene resides.
Genetic data tells you that this probe
detects a region of DNA that is extremely close to your gene.
Therefore, you isolated phage
that hybridized to this probe. The following gel is an agarose gel of EcoR1 digested phage
DNAs after electrophoresis.
Lanes containing different phage DNAs are labeled A – E.
The rightmost lane is a 1 kb marker. Each band is 1 kb larger than the band below it, starting
with 1 kb at the bottom, and ending with 10 kb at the top of the gel. NOTE: The two vector arms,
which should appear in each lane as 10 and 9 kb fragments, are not shown on this gel.
Darker bands may have
From these data, construct a map of the order of EcoRI fragments in the genome showing
the overlap of the various phage. If any fragments cannot be definitively ordered, enclose
them in parentheses.
Answer: 4 points (2 points for diagram showing overlap and 2 points for correct order.) Key:
1kb band in A is darker, suggesting 2 fragments of same size. Treat this as a deletion problem,
only here you’re dealing with numbers (sizes) instead of letters. Make a list of what fragments
each phase has: A(1,4,1); B (6,3,2); C (1,4,5); D (6,3,1); E (4,3,1). I would start with 2 phage
that share a lot of fragments such as B/D, which have 6 and 3 in common and therefore overlap
at these sites. Since 6/3 are in common, 2 & 1 are to the opposite sides = 2, (6,3),1. If you add E
to those two, E has frags 3 & 1 and a new one #4 so you can order the above to get: E BD:
2,6,3,1,4. Now add phage C to get 2,6,3,1,4,5. Phage A has 2 fragments of the same size so this
is a bit more tricky since the order of A could possibly be 1,1,4 or 1,4,1. So we have to propose
that ACE = 3,1,4,1,5 so the final order is 2,6,3,1,4,1,5.