Topic 7: Nucleic acids & proteins HL

7.1.1 Describe the structure of DNA, including antiparallel strands, 3'-5' linkages and hydrogen bonding between purines and pyrimidines.

• Sugar phosphate backbone consisting of phosphate groups attached to carbons 3 and 5 of the deoxyribose sugar, called the 3' - 5' linkage.
• Sugar phosphte chains form anti-parallel strands because they are opposite each other in direction

7.1.2 Outline the structure of nucleosomes

• Nucleosome consists of DNA wrapped around eight histone proteins which is held together by another histone protein.

(eight) histone (proteins);

DNA wrapped around histones/nucleosome;

further histone holding these together;

Do not allow histone wrapped around DNA.

7.1.3 Nucleosomes help to supercoil chromosomes and help to regulate transcription.

7.1.4 Distinguish between unique and highly repetitive sequences in nuclear DNA.