Chapter 16 Flashcards
who introduced the double helical model for DNA in 1953?
James Watson and Francis Crick
what is encoded in DNA?
hereditary information
DNA directs the development of what?
biochemical, anatomical, physiological, and behavioral traits
how was DNA’s role in heredity first discovered?
by studying bacteria and the viruses that infect them
Frederick Griffith did what to discover the genetic role of DNA
worked with two strains of bacterium, one pathogenic and one harmless
-he mixed heat killed remains of the pathogenic strain with living cells of the harmless strain, some living cells became pathogenic
transformation
a change in genotype and phenotype due to assimilation of foreign DNA
bacteriophages (or phages)
viruses that infect bacteria
DNA is a _____ of nucleotides each consisting of a _____ base, a _____, and a ______ group
- polymer
- nitrogenous
- sugar
- phosphate
what are Chargraff’s rules
- The base composition of DNA varies between species
2. In many species the number of A and T bases are equal and the number of G and C bases are equal
nitrogenous base
a nitrogen containing molecule
What does the 5’ end mean and what does the 3’ end mean?
5’ and 3’ refer to the number of carbon in the sugar (deoxyribose) molecule in the DNA
5’ end attaches to a phosphate and if it is an end than it is still attached to a phosphate and it is the 5th carbon in the molecule
3’ end can also attach to a phosphate but if it is an end it is not attached to anything and this is the 3rd carbon in the molecule
a bunch of nucleotides make what?
A DNA molecule:
Structure of DNA back bone…
(nucleotide 1) - (nucleotide 2)
(nucleotide 3) - (nucleotide 4)
what makes up a nucleotide? (3)
a phosphate group, a sugar molecule, and a nitrogenous base (either Thymine, Adenine, Cytosine, and Guanine)
What did Franklin’s X-ray crystallographic images of DNA enable Watson to deduce?
That DNA was helical
- as well as the width of the helix and the spacing of the nitrogenous bases
- the pattern in the photo suggested that the DNA molecule was made up of two strands, forming a double helix
- concluded that there were two outer sugar-phosphate backbones, with the nitrogenous bases paired in the molecules interior
what brings together the two nitrogen bases?
a hydrogen bond
antiparallel
their subunits run in opposite directions
Adenine pairs with….
Thymine
Guanine pairs with….
Cytosine