DNA & Chromosomes (Video 1 in 2.5 Series)

Introduction to DNA Structure00:00:28

DNA is a double helix molecule composed of two anti-parallel sugar-phosphate backbones connected by nitrogenous bases (adenine, thymine, cytosine, and guanine) that follow the complementary base pairing rule.

DNA Packaging into Chromatin and Chromosomes00:03:30

DNA is wrapped around histone proteins. It exists as loosely packed chromatin for replication and reading, but condenses into tightly packed chromosomes to ensure safe division during mitosis and meiosis.

Sister Chromatids vs. Homologous Pairs00:05:23

Sister chromatids are identical copies of a single chromosome joined at the centromere after DNA replication. In contrast, homologous pairs consist of two non-identical chromosomes of the same type, one inherited from each parent.

Chromosome Number: Haploid and Diploid00:09:10

Somatic cells are diploid (2n), containing 46 chromosomes (23 homologous pairs), while gametes are haploid (n), containing 23 chromosomes representing a single set.