DNA and RNA Flashcards
Describe the experiment Griffith did to discover bacterial transformation Describe Avery, Macleod and McCarty DNA discovering experiment Explain how genetic material of phage T2 is DNA Draw nucleotide basic structure Know DNA properties Identify purine and pyrimidine bases Understand difference between Deoxyribose and ribose Know that DNA can adopt different forms
What animal did Griffiths experiment involve and what was the bacterium? (3)
The animal was mice 2 strains of serotype: Serotype 2 (R) - non pathogenic Serotype 3 (S) - pathogenic
What did Griffith find when he changed conditions of the bacteria? (3)
Heat-killed S type 3 - survived (bacteria dead)
Heat killed S type 3 and normal R type 2 - mouse died
Some property of the dead, S 3 can transform the live R 2 bacteria (DNA released, R converted to S)
What did Avery discover from Griffiths experiment?
The transforming principle was DNA
Describe the Avery, MacLeod and McCarty experiment: (5)
Used 75L of heat-killed S3 cells
Removed lipids - extract still active
Removed protein - extract still active
Removed polysaccharide - extract still active
Only DNA remaining - extract still active
What did the Hershey-Chase experiment demonstrate?
It demonstrated that the genetic material is DNA
Describe the stages of the Hershey-Chase experiment: (5)
35S Coat proteins and 32P DNA applied to separate pellets
Blended separately (phage ghosts appear)
Centrifugation
35S remained in the supernatant
32P DNA was mainly in the pellet
What is the evidence for DNA structure? (3)
- Nucleotide structure known
- X-ray diffraction - helical structure
- Chargaff’s Law’s - purines (A G) Pyrimidines (T C)
What are Chargaff’s Law’s? (2)
- Total pyrimidines (T,C,[U]) = total purines (A,G)
2. T=A and C=G
How many H bonds do A and T have and how many do C and G have?
A=T - 2
C≡G - 3
What are the 3 main components of a nucleic acid?
Phosphate
Pentose sugar
Purine or pyrimidine base
What is the difference between ribose and deoxyribose?
On the deoxyribose there is no hydroxyl on the 2 carbon
What is a nucleoside?
Sugar + base
What is a nucleotide?
Sugar + base + phosphate
What are the key properties of DNA? (2)
Double alpha helix structure
2 anti-parallel strands held together by H bonds between base pairs
What type of handed helix is DNA?
Right handed helix
What are the 3 forms of DNA?
A
B
Z
What are the key properties of A DNA? (4)
Right handed
11 base pairs in a turn
More compact than B - smaller distance between bases
Large helix diameter
What are the key properties of B DNA? (4)
Common DNA found in cells
Right handed
10 base pairs in a turn
Large major groove
What are the key properties of Z DNA? (5)
Found in vitro, just GCGCGCGC Left handed Narrow diameter Stretched 12 base pairs in a turn
What happens if you apply heat to DNA and then cool it again?
It denatures and then renatures
What are the 3 RNAs?
mRNA - messenger
rRNA - ribosomal
tRNA - transfer
What is different about the structure of RNA to DNA (3)
Contains uracil instead of thymine
Contains ribose instead of deoxyribose
Single stranded - single polynucleotide chain
What is the structure of RNA?
t shape, clover leaf
What does the Hershey-Chase experiment show?
When bacteriophages infect bacteria, their DNA enters the host bacterial cell, but most of their protein does not.
