Exam 3 Notes

Question 1

Griffith and Avery

Answer 1

first experiement
used s strain (virulent) and r strain bacteria streptococcus pneumoniae and tried to heat kill it but it still left dead mice. this means that something is transferred to bacteria even after heat killing

Question 2

Avery and Macleod, McCarty

Answer 2

put some s strain and some heat killed into different tubes with RNAase, protease and DNAase. and DNAase was the only one that survived which proved DNA was the molecule of heredity

Question 3

Hersey and Chase

Answer 3

used half lives and bacteriophages so label the phosphates on DNA and the protein coat

Question 4

bacteriophage

Answer 4

a virus that only attacks bacteria —> produces more virus that keeps killing bacteria

Question 5

Chargaff’s rule

Answer 5

AT pairs together CG pair together in DNA

RNA: AU, CG

Question 6

DNA structure

Answer 6

antiparallel

• grows from 3’ end (phosphate is on 5’ end, oh is on 1’)
• has phosphodieter bonds
• cases are connected through hydrogen bonds
• has major and minor grooves: DNA has grooves like a key that come from the particular DNA sequence shape that tell different proteins to bind to them (not only for transcription, but also to label where particular genes are)

Question 7

draw a DNA diagram

Answer 7

lesson 20

Question 8

Meselson and stahl

Answer 8

used isotope n14 to incorporate radioactivity into DNA to show that 1) DNA is radioactive then 2) one radioactive strand and one regular strand 3) 2 regular strands and 2 strands with half radioactive to show semiconservative replication

Question 9

replication

Answer 9

helices unwinds from 5’ end to 3’ end making a replication bubble

• ssb’s keep it open
• topoisomerase keeps helix from getting too tense (cuts one base and unswivels)
• DNA pol III makes DNA and also checks the bases
• primase makes RNA primer
• Excisase will replace the RNA by excising it and replace it with DNA
• DNA ligase makes bonds after the Okazaki fragments have been cut out by excisase
• leading strand is made from 5’ to 3’ antiparallel (same direction as helicase)

Question 10

transcription to make RNA vs replication

Answer 10

uses RNA polymerase instead of DNA polymerase
Also does not use primase (short stretch of RNA to make the DNA polyermase)
Another bit of evidence on why RNA came first

Question 11

3 types of RNA

Answer 11

1) ribosomal RNA rRNA
2)messenger RNA mRNA

3) transfer RNA tRNA

Question 12

nucleus has

Answer 12

pores and both replication and translation occur there

Question 13

Promoter

Answer 13

sequence of DNA that allows the RNA POL to bind to it

Question 14

transcription

Answer 14

By adding a phosphate to RNA pol II, it starts matching up base pairs
Then the RNA falls off later on (since the AU paring is weak)
It will then go to post transcriptional modification

Question 15

post modifications of made RNA

Answer 15

• spliceospome will cut out the introns by pulling axons together
• end result moves to cytoplasm
• adds 5’ GTP cap using capping enzyme and adds a poly A tail using poly-A tail polymerase
• now you can call it mRNA

Question 16

tRNA

Answer 16

single strand that coils around and has a special structure
made in cytoplasm
Transfers amino acids
Contains three bases (“words”) called the anti-codon
Enzyme that matches the amino acid to the tRNA is called aminoacyl-tRNA synthase
The codons are sitting on the mRNA

Question 17

Ribosomes

Answer 17

have both small and large subunits
Designated as “s” which means sediment
Not a complete unit until translation occurs

Question 18

Translation

Answer 18

Has 4 factors:
initiaion factor 
elongation factor GTPase
peptidyl transferase
translocate

Question 19

initiation factor

Answer 19

finds beginning of RNA with the cap and grabs a small and large subunit of ribosomes. Lines up first and second codons with particular sites on the ribosome. Also takes the first tRNA and adds to the p site

Question 20

what ribosome does in translation

Answer 20

takes the first codon and puts it in the “P’ peptide site
Takes the second codon and puts it on the “A” site
AUG is the start codon
tRNA brings the Met with anticodon UAC

Question 21

elongation factor

Answer 21

uses GTP to put aa-tRNA and add to A site
The breakdown of GTP takes time so during this time, the elongation factor tries to wiggle the codon and anticodon to match. If it doesn’t fit in that time, it will leave and try to grab another amino acid

Question 22

Peptidyl transferase

Answer 22

third factor

Takes the bond from met and tRNA and swaps it to met and the next amino acid

Question 23

translocase

Answer 23

4th factor
Uses GTP to make GDP and p
Will make sure that dipeptides are in the p site
Will always make sure that the ribosome is shifting to make sure it is at the right site