PSY355H5 Study Guide - Final Guide: Y Chromosome, Intron, Exon
Document Summary
Dna is comprised of 4 different building blocks, so called nucleotide bases. Adenine (a), thymine (t), guanine (g) and cytosine (c). The base pairs are attatched to a sugar phosphate backbone to form one of two strands of a dna molecule. The two strands are bonded together by the base pairs. A only bonds with t and g only bons with c. this results in 2 mirror image, or complementary, strands. Each of the strands has a twisted or helical structure and when bonded they may form a double helix. The direction of each strand in a dna molecule is defind as 5" for the beginning, and 3" for the end. The 5" and 3" terms refer to the position of the bases relative to the sugar molecule in the dna backbone. These are important reference points for navigating through the genome. The 2 complementary strands are bound in opposite directions to each other.
