Test2 problem session Flashcards
Purine
- 2 rings
- adenine and guanine
Pyrimidine
- 1 ring
- cytosine and thymine
what is the diameter of the DNA
2nm
what is the distance per turn of helix?
3.4nm
What is the distance between base pairs
.34nm
how many base pairs per turn of a helix?
10 BP
When labeling diagram where is 3’end?
where the OH is
5’ is where the phosphate is at the top
Which way does Z-DNA coil?
left-handed manner
Topoisomerase
enzyme that relieves stress in the DNA by nicking the DNA
Griffeth
Observations: S strains kills mic Heat-killed S strain does not kill mice R strain does not kill mice. Heated S + R strains does kill mice
Conclusion:
The process that changes the avirulent strain to a virulent strain is called transformation
Avery, MacLeod, and McCarty
Only treatment of the S cell extract with DNase kept the extract from transforming the R cells
-DNA is required for transformation
Hershey and chase
Radiolabel phages protein coade (35s) or DNA (32p) and observed what got passed on. The bacteria had a lot of 32P and very little 35s after phage infections
-DNA is the infectious part of bacteriophages
Wilkins and Franklin
X-ray crystallography study of DNA
-x-RAY scattered picture of crystallized DNA looks like a helix 2 nm in diameter, with 2 regularities, 3.4 nm and .34 nm
Conclusion
-DNA is helical with more than one helix with repeating patterns
Chargraff
Did a quantitative analysis of DNA base pairs
observed that the base composition from different species in table.
concluded: G=C and A=T
A+G=C+T
Watson and crick
structure of dna
Chromatin
is the complex of DNA, chromosomal proteins and RNA within a nucleus
What does the first level of DNA packaging involve?
histone proteins.
Histone proteins
Proteins are rich in the positively charge amino acids, LYSINE and ARGININE.
-they are capable of binding to DNA electrostatic ally.
What does an octomer consist of?
two each of H2A, H2B, H3, and H4 with approx. 146 bp of DNA to form the nucleosome core particle
What is the second level of DNA packaging?
When the nucleosomes are coiled into 30 nm chromatin fiber that is approximately 30 nm in diamter
Meselsohn and Stahl
Label Used: 15N
Technique used: Density graient centrifugaiton
Observation prior to replication: 1 heavy band
Results after 1 round of rep. = 1 intermediate band rules out conservative
results after 2 rounds of replication= 1 intermediate band and 1 light band
Taylor, Woods, and Hughes
Label used: 3H
technique used: autroradiography
observation before rep. no radioactivy
after one round of replication: both sister chromatids labeled
after 2 rounds of replication: one one chromatid labeled
What are nucleotide joined together by?
phosphodiester bonds
Helicase
unwinds the DNA
RNA primase
lays down the RNA primer since DNA polymerase requires a free 3’ OH
SSB
binds to the strand of DNA to keep them separated
Gyrase
relieves tension due to supercoilining
DNA polymerase
removes primer and replaces it with DNA.. feels in gaps
Ligase
seals the new strand by repairing the remaining nick in the DNA
Cis acting elements
DNA sequences that signal cell about gene and regulation
trans acting factors
protein that recognized cis elements and helps polymerase to start
