Question

Lactose tolerance (the ability to process milk during adulthood) was actually a mutation that arose randomly during evolutionary history. Now, it is estimated that 1/3 of the world's population is lactose tolerant. Explain how this mutant allele might have increased in frequency to reach 1/3 of the world's population.

Dwarfism can be caused by a shortage of human growth hormone. Bacteria can be used to produce the protein. Describe the steps you would take to use molecular cloning to insert a human growth hormone gene into a bacterial plasmid

Answer 1

1. The lactose tolerance mutation would become common if it provided a survival and reproductive advantage in a particular environment. For example, in a population with domesticated cows, where milk is available, the ability to drink milk might have been advantageous in periods of drought or when food was limited.

2. The plasmid is cut open by the help of restriction enzymes. Gene of interest i.e growth hormone gene is inserted into the plasmid and the ends are sealed by the help of DNA ligase. The plasmid is inserted into bacteria. The bacteria are checked by antibiotic selection method to check which ones have incorporated the recombinant plasmid. Those bacteria re separated which contains the recombinant plaid from those ones who do not. Grow up lots of plasmid-carrying bacteria and use them as "factories" to make the protein. Harvest the protein from the bacteria and purify it.