Chapter 16 - Molecular basis of Inheritance and Introduction to Polymerase Chain Reaction Flashcards
Who introduced the double helix model of a DNA strand?
James Watson and Francis Crick
In 1953
who performed experiments showing that DNA is the genetic material of a phage known as T2?
Alfred Hershey and Martha Chase’
in 1952
Viruses are made up of what two things?
1. Protein
2. DNA
DNA is a polymer composed of many nucleotides. Each nucleotide is composed of what three components?
1. A nitrogenous base,
2. A sugar,
3. A phosphate group
What were Chargaff’s two rules relating to genetic matching (A-T, C-G)
Rule #1:
A=T and C=G (not exactly, but close)
Rule #2:
The A-T : C-G ratio is different between different organisms
________ ________ and _______ _________were using a technique called X-ray crystallography to study molecular structure
Maurice Wilkins and Rosalind Franklin
- Franklin produced a picture of the DNA molecule using this technique
- Franklin’s X-ray crystallographic images of DNA enabled Watson to deduce that DNA was helical
- The X-ray images also enabled Watson to deduce the width of the helix and the spacing of the nitrogenous bases. The width suggested that the DNA molecule was made up of two strands, forming a double helix.
What did Rosalind Franklin deduce from the discovery of the double helix?
Franklin had concluded that there were two antiparallel sugar-phosphate backbones with nitrogenous bases pair in the molecule’s interior.
What are the 4 molecules that make up strands of DNA?
Purines
Adenine
Thymine
Pyrimidines
Cytosine
Guanine
What are the pairings for the 4 molecules that make up DNA? (A,T,G,C)
Adenine-Thymine
A & T
Guanine-Cytosine
G & C
Purines & Pyrimidines are not the same size, So, A-A would be different width than T-T
Instead… pairing a purine with a pyrimidine resulted in a uniform width consistent with the X-ray
How wide is a DNA molecule? (in nm)
2nm
