Genetic Concepts Lecture

Key Topics

• DNA structure and function
• Chromosome and Chromatid differentiation
• Enzyme function in DNA replication
• Concept of leading and lagging strands in DNA synthesis

DNA Structure and Function

• DNA is composed of a sugar-phosphate backbone and nitrogenous bases (A, T, C, G).
• It exists in a double helix structure where bases pair A with T and C with G.
• DNA replication is semi-conservative, meaning each new DNA molecule has one original and one new strand.

Chromosome vs. Chromatid

• Chromosome: a long continuous thread of DNA that consists of numerous genes.
• Chromatid: Each half of the duplicated chromosome.
• Before cell division, chromosomes duplicate, and each half is known as a chromatid.
• Post-replication, sister chromatids separate to ensure each new cell receives a complete set of chromosomes.

Enzyme Function in DNA Replication

• Helicase unwinds the DNA double helix.
• DNA polymerase synthesizes the new DNA by adding nucleotides matching the original strand.
• Ligase seals gaps between the Okazaki fragments in the lagging strand.

Leading vs. Lagging Strands

• DNA synthesis is continuous on the leading strand and discontinuous on the lagging strand.
• Okazaki fragments are short sequences synthesized on the lagging strand.
• The lagging strand requires more enzymes and processes to complete its synthesis.