Molecular Inheritance

Why did scientists think proteins carried genetic information?

Proteins have more variety and complexity than DNA’s four nucleotides.

What did Griffith’s experiment demonstrate?

DNA can transform bacteria, transferring hereditary traits.

What did Hershey and Chase’s experiment show?

DNA, not protein, is the genetic material.

What are Chargaff’s rules?

A = T and C = G; DNA composition varies between species.

Who discovered DNA’s double helix?

Rosalind Franklin produced X-ray images; Watson and Crick modeled it.

What are purines and pyrimidines?

Purines: A, G (double ring); Pyrimidines: C, T (single ring).

How do base pairs bond?

Hydrogen bonds — A–T (2), C–G (3).

What is semiconservative replication?

Each new DNA molecule has one parental and one new strand.

What enzyme unwinds DNA?

Helicase

What enzyme synthesizes RNA primers?

Primase

What does DNA ligase do?

Joins Okazaki fragments on the lagging strand.

In what direction is DNA synthesized?

5′ → 3′ direction

What are leading and lagging strands?

Leading = continuous; Lagging = discontinuous, Okazaki fragments.

What is a telomere’s role?

Protect chromosome ends from degradation.

What are histones and nucleosomes?

Histones are proteins; DNA wraps around them forming nucleosomes.

What is heterochromatin vs. euchromatin?

Heterochromatin = condensed, inactive; Euchromatin = loose, active.