Flashcards Ch 16 Part I - Structure of DNA

Front

tetranucleotide hypothesis

Back

DNA structure hypothesis from 1897-1947; Scientists thought DNA molecules were composed of four nucleotides repeating in the same order down the polymer

Front

In what direction is this polynucleotide sequence facing --> 5' to 3' or 3' to 5'?

Back

3' to 5' because carbon #3 points up on every nucmeotide and carbon #5 points down on every nucleotide

Front

Method used by Chargaff to study DNA

Back

Chargaff collected DNA samples from several organisms and used paper chromatography to separate the nitrogenous bases.

Front

Erwin Chargaff's scientific contribution

Back

1) DNA composition is species-specific

2) The amounts and ratios of bases vary from one species to another.

Front

Regularity in base ratio

Back

In every species studied, the number of adenine (A) bases equals the number of thymine (T) bases, and the number of guanine (G) bases equals the number of cytosine (C) bases.

Front

Watson and Crick's discovery

Back

Watson and Crick discovered the double helix by building models to conform to X-ray data.

Front

Role of Rosalind Franklin

Back

Watson saw an X-ray photo of DNA produced by Rosalind Franklin that helped them figure out the structure of DNA.

Front

Antiparallel

Back

The two sugar-phosphate backbones of the helix are antiparallel, meaning they run in opposite directions (One is 5' to 3' and the other is 3' to 5').

Front

Why must a purine pair with a pyrimidine?

Back

A purine base on one strand pairs with a pyrimidine base on the other strand to maintain consistent width.

Front

What determines which purine will pair with the specific pyrimidine?

And which bases pair together?

Back

The structure of a base dictates which pairs of bases can form hydrogen bonds:
A pairs with T; C pairs with G.