Test2 problem session

Question 1

Purine

Answer 1

• 2 rings

- adenine and guanine

Question 2

Pyrimidine

Answer 2

• 1 ring

- cytosine and thymine

Question 3

what is the diameter of the DNA

Answer 3

2nm

Question 4

what is the distance per turn of helix?

Answer 4

3.4nm

Question 5

What is the distance between base pairs

Answer 5

.34nm

Question 6

how many base pairs per turn of a helix?

Answer 6

10 BP

Question 7

When labeling diagram where is 3’end?

Answer 7

where the OH is

5’ is where the phosphate is at the top

Question 8

Which way does Z-DNA coil?

Answer 8

left-handed manner

Question 9

Topoisomerase

Answer 9

enzyme that relieves stress in the DNA by nicking the DNA

Question 10

Griffeth

Answer 10

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

Question 11

Avery, MacLeod, and McCarty

Answer 11

Only treatment of the S cell extract with DNase kept the extract from transforming the R cells

-DNA is required for transformation

Question 12

Hershey and chase

Answer 12

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

Question 13

Wilkins and Franklin

Answer 13

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

Question 14

Chargraff

Answer 14

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

Question 15

Watson and crick

Answer 15

structure of dna

Question 16

Chromatin

Answer 16

is the complex of DNA, chromosomal proteins and RNA within a nucleus

Question 17

What does the first level of DNA packaging involve?

Answer 17

histone proteins.

Question 18

Histone proteins

Answer 18

Proteins are rich in the positively charge amino acids, LYSINE and ARGININE.

-they are capable of binding to DNA electrostatic ally.

Question 19

What does an octomer consist of?

Answer 19

two each of H2A, H2B, H3, and H4 with approx. 146 bp of DNA to form the nucleosome core particle

Question 20

What is the second level of DNA packaging?

Answer 20

When the nucleosomes are coiled into 30 nm chromatin fiber that is approximately 30 nm in diamter

Question 21

Meselsohn and Stahl

Answer 21

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

Question 22

Taylor, Woods, and Hughes

Answer 22

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

Question 23

What are nucleotide joined together by?

Answer 23

phosphodiester bonds

Question 24

Helicase

Answer 24

unwinds the DNA

Question 25

RNA primase

Answer 25

lays down the RNA primer since DNA polymerase requires a free 3’ OH

Question 26

SSB

Answer 26

binds to the strand of DNA to keep them separated

Question 27

Gyrase

Answer 27

relieves tension due to supercoilining

Question 28

DNA polymerase

Answer 28

removes primer and replaces it with DNA.. feels in gaps

Question 29

Ligase

Answer 29

seals the new strand by repairing the remaining nick in the DNA

Question 30

Cis acting elements

Answer 30

DNA sequences that signal cell about gene and regulation

Question 31

trans acting factors

Answer 31

protein that recognized cis elements and helps polymerase to start