Lecture 4

What are the three major components identified by Phoebus Levene that make up a nucleotide?

Sugar (deoxyribose), phosphate, and nitrogenous base.

What was Levene's tetranucleotide hypothesis?

He proposed that all nucleotides (A, T, C, and G) would fit together in a circular structure with equal proportions.

Who were the scientists that contributed to demonstrating that DNA is the molecule of heredity?

Frederick Griffith, Avery, McLeod, McCarty, Hershey, and Chase.

What did William Asbury contribute to the understanding of DNA?

He developed X-ray diffraction techniques that revealed DNA's regular structure and base stacking arrangement.

What is Chargaff’s first rule regarding the composition of DNA?

The number of guanines (G) equals the number of cytosines (C), and the number of adenines (A) equals the number of thymines (T).

What was the significance of Rosalind Franklin’s work on DNA?

She generated high-quality X-ray diffraction images that demonstrated DNA's helical shape and provided crucial information on its structure.

What critical piece of information did Watson and Crick gain from Rosalind Franklin’s work?

The symmetry of DNA and the placement of phosphates on the outside of the molecule.

What does the term 'base pairing' in DNA refer to?

Adenine pairs with thymine (A-T) and guanine pairs with cytosine (G-C) through hydrogen bonds.

What was the outcome of Watson and Crick's publication in 1953?

They proposed the double helical structure of DNA, earning them the Nobel Prize in 1962.

Why is Rosalind Franklin not a Nobel Prize recipient despite her contributions to DNA structure?

She was not included, and her work was not adequately recognized during her lifetime.