BIOL1020 : BIOL1020 Module 2 - Molecular Genetics
Document Summary
Dna exists as a helix of two antiparallel strands which interact through weak hydrogen bonds. Have direction due to 3" and 5". 5" end has a phosphate group where 3" has an oh group. Dna consists of four subunits: a,c, g & t. Adenine and guanine = purines (two carbon-nitrogen rings) Cytosine, thymine and uracil = pyrimidines (one carbon-nitrogen ring) Both sugars are pentose sugars with 5 carbon atoms. Human chromosome may contain 50 to 250 million base pairs. To fit into nucleus the chromosome must be 10,000 times smaller. Dna associated with basic (positively charged) proteins (the histones) which form protein-dna complexes known as nucleosomes. Contains 200 nucleotides with other histones (proteins) (linked by histone h1) Interaction between histones" positive charge and negative charge of dna. Wound into solenoid-like structure with 6 nucleosomes per turn. Chromatin fibre packed into loops attached at intervals to a scaffold of protein.
