C11: Molecular Genetics (5088 COMBINED BIOLOGY)

MOLECULAR GENETICS adenine (A) cytosine (C) guanine (G) thymine (T) A-T, G-C A nucleotide consists of a: 1) (deoxyribose) sugar molecule 2) phosphate group 3) nitrogenous base STRUCTURE OF DNA - Made up of two anti-parallel polynucleotide strands. - Bases from one strand form weak hydrogen bonds with bases on the other strand according to rule of complementary base pairing. > Two hydrogen bonds are formed between adenine and thymine whereas three hydrogen bonds are formed between guanine and cytosine. - Uncoiled DNA molecule: structure looks like a “ladder” - Coiled DNA molecule – Double helix

How is a protein / polypeptide made? 1. In the nucleus, the message in the gene is copied into an mRNA (messenger RNA). 2. The mRNA travels to the cytoplasm and attaches to a ribosome.

3. As the ribosome moves along the mRNA, it synthesises a polypeptide. 4. When the ribosome leaves the mRNA, The polypeptide is released.