Question

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Define the term mutation. Based on your definition, predict whether mutations are more likely to be harmful or beneficial to an organism. Provide an explanation to support your answer.

Answer 1

Permanent change in nucleotide base of DNA sequence known as mutation. Change in DNA sequence leads to change in mRNA sequence and further changes in polypeptide amino acid sequence leads change in biological activities of organisms.

Harmful mutation

Change of one single nucleotide in beta hemoglobin polypeptide (GAG to GTG in DNA /GAG to GUG in mRNA) leads to change in glutamic acid to valine further changed the structure of hemoglobin leads formation of sickle hemoglobin and changed the RBC structure (sickle RBC) and decreases the oxygen carrying capacity. It an example for harmfull mutation.Further it is selected in the population because this mutation resistance to malaria infection in heterozygous individuals.

Others are BRCA 1 & 2 leads to human breast cancer and cistic fibrosis caused by mutation in CFTR gene (deletipn of 3 nucleotide leads to loss of phenylalanine at 508 position leads cistic fibrosis disease).

Beneficial mutation example

Mutation in CCR5 co receptor leads to resistance to HIV infection in CCR5 homozygous individuals is a beneficial mutation in europian population to stop spreading of hiv infection. They acquired this mutation from smallpox (new theory) or bubonic plague and because of selective pressure it is selected and spreads in European population but not in africa population.