Chapter 10 Flashcards
(22 cards)
What three general characteristics must the genetic material possess?
- The genetic material must contain complex information that encodes the phenotype
- The genetic material must replicate or be replicated faithfully.
- The genetic material must be able to mutate to generate diversity
What experiments demonstrated that DNA was the genetic material?
Avery, Macleod, and McCarthy demonstrated that DNA was the transforming material, then Hershey and Chase demonstrated that DNA was the genetic material in bacteriophage
What is transformation and how did Avery and his colleagues demonstrate that the transforming principle is DNA?
Transformation occurs when genetic material alters the genotype and phenotype of an organism when it uptakes the genetic material from the environment. The Avery experiment demonstrated that DNA was the transforming material by treating DNA with DNase, which destroyed the DNA, and showed that the transformation no longer took place.
How does an RNA nucleotide differ from a DNA nucleotide?
RNA - 2’OH and G, U, A, C nucleotides
DNA - 2’H and G, T, A, C nucleotides
How do purines and pyrimidines differ, and which letters are they in DNA and RNA?
purines - 2 membered ring - G, A
pyrimidines - 1 membered ring, T, C, U
How many hydrogen bonds do the base pairs have?
G has three with C
T has two with A
U has two with A
What different types of chemical bonds are found in DNA and where are they?
hydrogen bonds between the bases on the two strands of the helix
phosphodiester covalent bonds between all 3’ OH and 5’ phosphate groups between nucleotides
covalent between the phosphate groups, the phosphate, and the sugar, and between the sugar and the base
What are some important genetic implications of the DNA structure?
The instructions for making an identical copy of a DNA strand is contained in the strand itself. The nucleotide sequence codes for amino acids in proteins
What are hairpins and where do they come from?
hairpins are a secondary structure in DNA or RNA and are formed from hydrogen bonding between complementary nucleotides
What is DNA methylation?
when a methyl group (CH3) is covalently attached to the base
What did Franklin and Wilkins discover?
took x-ray diffraction pictures used in constructing the structure of DNA
What did Chargaff do?
determined regularity in ratios of the different bases in DNA
What did Watson and Crick do?
Worked out the helical structure of DNA by building models
What did Fraenkel-Conrat do?
conducted experiments showing that RNA can serve as the genetic material in some viruses
What did Griffith do?
demonstrated that heat killed bacteria could genetically transform live bacteria
If Avery, Macleod, and McCarty had found that samples of heat-killed bacteria treated with RNase and DNase transformed bacteria, but samples treated with protease did not, what conclusion would they have made?
protein is the genetic material
What is special about the tobacco mosaic virus?
RNA carries genetic information instead
Difference between monophosphates and triphosphates.
nucleotides in the DNA polymer are monophosphates
free nucleotides in the nucleus are triphosphates
Where do proteins usually bind in the DNA?
major groove
What is the difference between the B form, A form, and Z form of DNA structure?
A form - exists if less water is present, is shorter and wider, and is a right-handed helix
B form - exists when plenty of water surrounds the molecule and there are no unusual base sequences (most predominant), right-handed
Z form - left-handed helix where the backbone zigzags back and forth and results from a particular pair of base sequences
How does a hairpin structure form?
when sequences of nucleotides on the same strand are inverted complements (no hydrogen bonds because they are not complementary)
