Name:

1

• Name
• 1. Lac Operon
• A. Given the genotypes, fill in the
  appropriate phenotypes for LacZ and LacY. The
  inducer is lactose or IPTG.
• Phenotypes LacZ expression
  LacY expression
• Genotype no inducer inducer
  no inducer inducer
• 1 IOZY
• 2 IS O Z- Y-
• 3 IS OC ZY / FI-OZ-Y-
• 4 IOcZ-Y/ F I-OZY-
• 5 I-OCZY / F IS OZ-Y-

-
-

• B. Name one strain that indicates that OC is
  epistatic to IS, and what data tells you that?
• C. A new gene is identified that regulates the
  Lac operon, called Gene T.
  An allele Gene T-2 was
  analyzed.
  
  We know that Gene T acts in the glucose, ADC1,
  CRP pathway.
  The assays of Gene T function are done in a I-
  cell, with glucose present.
  (The phenotypes would be complicated by
  reporting LacZ expression with no glucose and
  with glucose column. However, you can figure this
  out using this data alone).

• i. Is Gene T-2 recessive or dominant (circle
  one)
• ii. Draw the glucose, Gene T,ADC1,CRP, LacZ,
  pathway, with gene order and sign of regulation
  (bar or arrow)
• How would you determine the order of CRP and
  ADC1, given the alleles in the table, and what
  result would you expect given you know their
  order?

LacZ expression
Strain
1. GeneT -
2. GeneT-2
3. GeneT-2/ Gene T -
4. ADC1
5. ADC1 GeneT-2
6. ADC1- -
7 . ADC1- Gene T-2
8. CRP - -
9. CRP- GeneT-2 -
2

• 2 . An FLeu1 plasmid is present in a bacterial
  strain. The F has only the Leu1 gene and has no
  IS nor transposon sequences. An F without IS
  nor transposons cannot form an Hfr. However, this
  FLeu1 can form an Hfr. The bacterial genome has
  a copy of the Leu1 gene as well.
• The FLeu1 is in a strain that has Arg2 Leu1
  Ura3 in that order.
• You also have an F- strain that is Arg2- Leu1-
  Ura3-.
• a. How does the F Leu1 integrate into the
  bacterial chromosome? Diagram this.
• b. How many single crossovers does integration
  require?
• c. Imagine you had two tubes of bacteria, one
  has the FLeu1 and one is an Hfr as described in
  the first to questions, but you dont know which
  is which. You also have a F- that is Arg2-
  Leu1- and Ura3-. How could you determine
  genetically which tube had the Hfr bacterium?

3

• 3. Discuss the following briefly
• In an Hfr cross, do both the Hfr and F- need to
  have an intact RecA for recombinants to be
  formed?
• In conjugation between an Hfr and F-, how many
  crossovers are required to incorporate DNA from
  the Hfr into the F-.
• Doe the F- become an Hfr in the cross?
• In an Hfr Leu1 Arg2 Ura3 x F- leu1- arg2-
  ura3- cross, how can you tell what the gene order
  is if the genes are separated by 10 minutes each?
  Draw the kind of data you would get and indicate
  the gene order (you can make up the data). Label
  the Y axis,

DATA
Gene order
minutes
4

• 4. In an Hfr Leu2 Arg3 Ura34 x F- leu2- arg3-
  ura34- cross, how can you tell what the gene
  order is if Leu2 and Arg3 are not separated by
  even 1 minute. Genes may not be written in the
  order they appear in the genome!!!
• Gene transferred Frequency
• Leu Arg Ura 200
• LeuArg Ura- 120
• Leu-ArgUra 4
• Leu- Arg- Ura 90
• 5. Suppose you have a bacterial cell that
  responds to salt by making Gene X. You are
  determining the pathway by which salt activates
  Gene X. Given the data below, draw a Salt Pathway
  linking salt (to the left) and Gene X (to the
  right).
• Genotype Phenotype (Gene X protein made)
• no salt salt
• Wildtype -
• Gene A-1
• Gene A-1/GeneA -
• Gene B-1 - -
• Gene B-1/GeneB - -
• Gene A-1 Gene B-1
• Salt Gene X