B190 molecular basis inheritance lecture 1

DNA Structure and Base Pairing00:00:01

Overview of the DNA double helix structure, highlighting the sugar-phosphate backbone and the specific pairing of nitrogenous bases: adenine with thymine (two hydrogen bonds) and guanine with cytosine (three hydrogen bonds).

Anti-parallel Orientation and Purine-Pyrimidine Ratios00:01:15

Explanation of why DNA strands are anti-parallel and why a purine must always pair with a pyrimidine to maintain consistent width and experimental structural data.

Semi-conservative DNA Replication00:03:54

Explanation of the semi-conservative model, where parental DNA strands act as templates to synthesize new complementary strands, resulting in DNA molecules that are half-old and half-new.

Origins of Replication00:05:28

Discussion on how DNA replication begins at specific sequences called origins of replication, noting differences between circular bacterial chromosomes and linear eukaryotic chromosomes.