1. Unit 5 Review: Warm-ups

2. Wednesday January 3rd Warm-up #1 of 3 today
Meselson and Stahl did an experiment to test how DNA replicates. They grew bacteria in a medium containing heavy nitrogen (15N) and then transferred it to regular nitrogen (14N). They allowed the bacteria to replicate once and then twice. Which of the following test tubes below would be shown if the bacteria replicated:
- conservatively after ONE replication
- semiconservatively after TWO replications
- dispersive model after TWO replications
- semiconservatively after ONE replication

3. Wednesday January 3rd Warm-up #1 of 3 today
Meselson and Stahl did an experiment to test how DNA replicates. They grew bacteria in a medium containing heavy nitrogen (15N) and then transferred it to regular nitrogen (14N). They allowed the bacteria to replicate once and then twice. Which of the following test tubes below would be shown if the bacteria replicated:
B - conservatively after ONE replication
E - semiconservatively after TWO replications
D - dispersive model after TWO replications
D - semiconservatively after ONE replication

4. Wednesday, January 3rd Warm-up #2 of 3 todayB C D
Look at the gel to the left. Are the wells at the positive end or the negative end and why?
Look at the piece of DNA above that has been digested with a restriction enzyme. Which lane would have the digested piece of DNA in it?
Based on the SIZE of the fragment of DNA, the band closest to the well would represent which fragment? (which letter?)
Based on the SIZE of the fragment of DNA, the band furthest from the well would represent which fragment? (which letter?)
Which lane would represent the piece of DNA if it had NOT been digested by the enzyme? 1 2 3 4

5. Wednesday, January 3rd Warm-up #2 of 3 todayB C D
Look at the gel to the left. Are the wells at the positive end or the negative end and why? Negative end b/c DNA is negative and will run towards the positive side
Look at the piece of DNA above that has been digested with a restriction enzyme. Which lane would have the digested piece of DNA in it? Lane 1
Based on the SIZE of the fragment of DNA, the band closest to the well would represent which fragment? (which letter?) Fragment B (largest  travels the slowest)
Based on the SIZE of the fragment of DNA, the band furthest from the well would represent which fragment? (which letter?) Fragment A (smallest  travels the fastest)
Which lane would represent the piece of DNA if it had NOT been digested by the enzyme? Lane 3 1 2 3 4 B D C A

6. Wednesday, January 3rd Warm-up #3 of 3 today
This question is from your review WS
A eukaryotic gene has “sticky ends” produced by the restriction enzyme EcoRI. The gene is added to a mixture containing EcoRI and a bacterial plasmid that carries two genes, which makes it resistant to ampicillin and tetracycline. The plasmid has one recognition site for EcoRI located in the tetracycline resistance gene. This mixture is incubated for several hours and then added to bacteria growing in nutrient broth. The bacteria are allowed to grow overnight and are streaked on a plate using a technique that produces isolated colonies that are clones of the original. Samples of these colonies are then grown in four different media: nutrient broth plus ampicillin, nutrient broth plus tetracycline, nutrient broth plus ampicillin and tetracycline, and nutrient broth containing no antibiotics.
The bacteria containing the engineered/ recombinant plasmid would grow in
The nutrient broth and the tet broth only.
The nutrient broth only.
The amp broth and the nutrient broth.
The amp and tet broth only.
The nutrient broth, the amp broth, and the tet broth.
2. The bacteria containing the plasmid but not the eukaryotic gene, would grow
The nutrient broth plus amp, but not the broth containing tet.
The broth containing tet, but not the broth containing amp.
Only in the broth containing both antibiotics.
Only in the broth that contained no antibiotics.
In all four types of broth.

7. Wednesday, January 3rd Warm-up #3 of 3 today
A eukaryotic gene has “sticky ends” produced by the restriction enzyme EcoRI. The gene is added to a mixture containing EcoRI and a bacterial plasmid that carries two genes, which makes it resistant to ampicillin and tetracycline. The plasmid has one recognition site for EcoRI located in the tetracycline resistance gene. This mixture is incubated for several hours and then added to bacteria growing in nutrient broth. The bacteria are allowed to grow overnight and are streaked on a plate using a technique that produces isolated colonies that are clones of the original. Samples of these colonies are then grown in four different media: nutrient broth plus ampicillin, nutrient broth plus tetracycline, nutrient broth plus ampicillin and tetracycline, and nutrient broth containing no antibiotics.
The bacteria containing the engineered/ recombinant plasmid would grow in
The nutrient broth and the tet broth only.
The nutrient broth only.
The amp broth and the nutrient broth.
The amp and tet broth only.
The nutrient broth, the amp broth, and the tet broth.
2. The bacteria containing the plasmid but not the eukaryotic gene, would grow
The nutrient broth plus amp, but not the broth containing tet.
The broth containing tet, but not the broth containing amp.
Only in the broth containing both antibiotics.
Only in the broth that contained no antibiotics.
In all four types of broth.

8. Thursday, January 4th
Warm-up #1 of 3 today
1. If the nitrogen bases in a cell are made up of 42% cytosine, how much adenine is present in the cell?
2. What DNA sequence would code for
this polypeptide:
met – asp – his – gln
3. What amino acids would the following
mRNA sequence code for?
AGG UCC GAG AUU CGC
4. Code this mRNA into DNA:
UGC CAA UUU UGC ACG

9. Thursday, January 4th
Warm-up #1 of 3 today
1. If the nitrogen bases in a cell are made up of 42% cytosine, how much adenine is present in the cell? 8%
2. What DNA sequence would code for
this polypeptide:
met – asp – his – gln
TAC- CTA – GTA – GTT
CTG – GTG - GTC
3. What amino acids would the following
mRNA sequence code for?
AGG UCC GAG AUU CGC
arg- ser - glu – ile - arg
4. Code this mRNA into DNA:
mRNA-UGC CAA UUU UGC ACG
DNA - ACG GTT AAA ACG TGC

10. Thursday, January 4th Warm-up #2 of 3 today What is an operon?
What are the 3 parts to an operon?
What is a regulatory gene?
Regarding the Trp Operon:
Is it repressible or inducible?
Is it normally on or off?
Does it make a repressor in an active or inactive form?
Does it make tryptophan or break it down?
If there was a lot of tryptophan in the environment, would the operon be on or off?
Regarding the Lac Operon:
Does it make lactose (allolactose) or break it down?
Explain Positive gene regulation with respect to the Lac Operon.

11. SEE PICTURES ON NEXT SLIDE!
Warm-up #2 of 3 today
Thursday, January 4th
What is an operon? A genetic regulatory system found in bacteria in which genes coding for functionally related proteins are clustered along the DNA strand
What are the 3 parts to an operon? Promoter, Operator (on/off switch), genes it controls
What is a regulatory gene? Codes for the repressor (A PROTEIN!); usually found further up from the other genes
Regarding the Trp Operon:
Is it repressible or inducible? Repressible
Is it normally on or off? On
Does it make a repressor in an active or inactive form? Inactive
Does it make tryptophan or break it down? Makes it
If there was a lot of tryptophan in the environment, would the operon be on or off? It would be off because tryptophan acts as a corepressor and activates the repressor to turn the operon off.
Regarding the Lac Operon:
Is it repressible or inducible? Inducible
Is it normally on or off? Off (only on when allolactose present)
Does it make a repressor in an active or inactive form? Active
Does it make lactose (allolactose) or break it down? Breaks it down
Explain Positive gene regulation with respect to the Lac Operon. If there is glucose available, then there will be low levels of cAMP, and if there is lactose available, the operon will be on a little, but not too much because it can use glucose as an energy source. If there is no glucose but there is lactose, the levels of cAMP will be higher and it will bind to the CAP/CRP and make the operon turn on a LOT.
SEE PICTURES ON NEXT SLIDE!

13. Positive Gene Regulation
cAMP = cyclic AMP; accumulates when glucose (E source) drops (this is because glucose inhibits the enzyme adenylyl cyclase (think chapter 11!) from converting ATP  cAMP…so when there is low glucose, this step is not blocked and ATP is turned into cAMP, which obviously has less available energy)
CAP = Catabolite Activator Protein; activates transcription initiation of operons
Positive Gene Regulation
Positive Control = something that binds to the operon directly that switches it ON; the degree of transcription depends on the concentration of other substances
SO…Glucose drops = cAMP increases = CAP becomes active = transcription is ON

14. Thursday, January 4th Warm-up #3 of 3 today
A primary transcript of mRNA is 30 kilobases (kb) long, but the mature mRNA is 12kb in length. What modifications most likely resulted in the 18kb difference in length between the mature mRNA and the primary transcript? Where in the cell would this occur?
What would the length be of the mature gene x mRNA if the full-length gene is introduced and expressed in prokaryotic cells? Explain.

15. Thursday, January 4th Warm-up #3 of 3 today
A primary transcript of mRNA is 30 kilobases (kb) long, but the mature mRNA is 12kb in length. What modifications most likely resulted in the 18kb difference in length between the mature mRNA and the primary transcript? Where in the cell would this occur? This would happen in the nucleus and RNA processing would remove the introns therefore the mature mRNA would be shorter than the original.
What would the length be of the mature gene x mRNA if the full-length gene is introduced and expressed in prokaryotic cells? Explain. It would be 30 kb long because prokaryotic cells can’t do RNA processing so the introns would not be cut out.