Lecture 1: Introduction to Molecular Biology

Question 1

How does a geneticist define a gene?

Answer 1

A gene is a measurable unit of heredity which can exist in different forms.

Question 2

How does a biochemist define a gene?

Answer 2

A gene is a stretch of DNA which is transcribed into RNA (and usually then translated into protein).

Question 3

What is albinism and how does it arise?

Answer 3

Albinism is a lack of pigmentation in the skin, eyes and hair caused by a defect in melanin synthesis, resulting from a defect in a single gene.

The final step in the melanin synthesis is the conversion of tyrosine, the amino acid, to melanin. This conversion requires the enzyme tyrosinase. The defective gene which causes albinism causes the enzyme tyrosinase to be missing or defective.

Albinism is recessive, because one normal gene can code for tyrosinase. This means both alleles of the gene must be defective for albinism to arise.