Assignment: Sickle-cell anemia arises from a mutation in the gene for the chain

Question

Assignment:

Sickle-cell anemia arises from a mutation in the gene for the chain of human haemoglobin. The change from GAG to GTG in the mutant eliminates a cleavage site for the restriction enzyme MstII, which recognizes the target sequence CCTGAGG. In the figure below MstII sites are indicated by vertical lines and the size of DNA fragments represented by horizontal double-arrows is indicated in kilobasepairs (kbp). These findings form the basis of a diagnostic test for the sickle-cell gene.

a) Propose two methods - based on DNA analysis - for distinguishing between the normal and mutant gene

b) What would be the result of these analyses on DNA from a normal person and from a person carrying the sickle-cell gene?

Explanation / Answer

A- Restriction digestion with MstII in case of Normal person will give two bands one of 1200 basepair and another one of 200 base pair whereas in case of mutant person we will only one band of 1.4kb.

PCR- we can design primers for PCR. Length of the primer, which will be a reverse primer, will be 9 bp whose sequence will be CCTGAGGAG and forward primer. In case of normal individual we will get the band of 1.4 kb and in case of mutant, we will not any band.

B- Normal person will give two bands one of 1200 basepair and another one of 200 base pair whereas in case of mutant person we will only one band of 1.4kb

In case of normal individual we will get the band of 1.4 kb and in case of mutant, we will not get any band upon PCR.

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