13. ***Bonus* (8 pt) A gene for that normally produces brown hair is linked to 3

Question

13. ***Bonus* (8 pt) A gene for that normally produces brown hair is linked to 3 Hindlll restriction enzyme sites (solid vertical lines on scheme below). A dominant allele produces a black hair phenotype, and this allele is associated with another mutation that destroys the middle of the 3 linked Hindlll sites. A woman with black hair has two children with a man with brown hair. The siblings both result from eggs where there was a crossover event at the position of the dotted line in the image below. One has black hair (child black), and the other has brown hair (child brown). Show how a Southern Blot would look with this family's DNA digested by Hindl and detected with the indicated probe. 1000 500 200 100bp 200bp brown gene 100 probe 2 points for each column black gene*

Explanation / Answer

When brown hair digested with HindIII RE, it will give two fragment

One fragment = 100 bp

Second fragment=200bp

But probe binds only at the 200bp fragment. So, when brown hair men's DNA was digested with HindIII RE, it will give only single band at a 200bp position in the blot.

Father- Band will come at the 200bp position

But in black hair (mother) DNA- only two restriction sites are there, so when digested with HindIII it will give 300bp fragment having probe binding site.

Mother-Band will come at a 300bp position in blot

Child brown-After crossing it will have only two Restriction sites, so when digested with HindIII. The band will come at the 300bp position.

Child black- After crossing it will have three restriction site and the band will come at 200 bp position in the southern blot.

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