Question

I really need help with these questions!!

2. Bernard Davis tested the "cross-feeding" interpretation of some data that showed the phenotype of one microbe as capable of being changed by another microbe. His contribution can be summarized as:

A) using one strain of microbes as food for another, and then evaluating the impact upon microbial phenotype.

B) combining microbes with complementing auxotrophs in a single tube and then analyzing the cells of gene exchange.

C) placing a barrier between bacterial strains with complementing auxotrophs to assess whether contact between cells was required for genetic exchange.

D) using fungi to feed bacterial strains with unusual auxotrophic mutations.

E) Davis was not a significant contributor to this research question.

Answer: ___

9. The lac repressor protein controls expression of the lac operon by binding to the:

            A) lac structural genes to repress expression.

            B) lacZ and lacY genes only to repress expression.

            C) lac operator site to repress expression.

            D) lac promoter site to repress expression.

            E) All of the answer options are correct.

Answer: ___

15. The “domain-swapping” experiment that grafts the Gal4 activation domain to the LexA DNA-binding domain generates a chimeric protein that will:

A) bind to the Gal4 site.

B) bind to the LexA site.

C) activate transcription of the Gal4 gene.

D) activate transcription of the Gal7 gene.

E) All of the answer options are correct.

Answer: ___

17. Describe the process of creating cDNA from mRNA, including any enzymes involved. What is the primary benefit of creating cDNA rather than studying mRNA directly? (6 pts)

18.) When attempting a targeted gene knockout using mouse embryonic stem cells, there are three possible outcomes: targeted knockout, ectopic insertion, and no insertion. What procedures can be used to select for cells that only have the targeted gene knockout? (9 pts)

19.) Describe why Jacob and Monod used IPTG as a synthetic inducer during their experiments investigating the genetic control of the lac operon. (6 pts)

20.) Describe the function of the CAP-cAMP system in bacteria. Why does it regulate several operons related to metabolism? (7 pts)

21.) Many DNA-binding proteins that affect gene expression are allosteric. What is allostery and why is it such a common mechanism of gene regulation? (7 pts)

22.) A number of mutations affect the expression of the lactose operon in E. coli. Complete the table given below. Use + to indicate that a functional enzyme is synthesized and - to indicate that a functional enzyme is not synthesized. (12 pts)

	Inducer (IPTG) absent		Inducer (IPTG) present
	b-Galactosidase	Permease	b-Galactosidase	Permease
a) I+ O+ Z+ Y+
b) IS O+ Z+ Y+
c) I– O+ Z+ Y+
d) I+ OC Z+ Y+
e) IS OC Z+ Y–
f) I+ OC Z+ Y–/I– O+ Z– Y+

Answer 1

2) OPTION C

placing a barrier between bacterial strains with complementing auxotrophs to assess whether contact between cells was required for genetic exchange.This is the contribution by the bernard Davis testing cross feeding

9) OPTION C -

lac operator site to repress expression.

The lac repressor protein binds to the operator and blocks RNA polymerase from binding to the promoter and transcribing the operon. The promoter is the binding site for RNA polymerase.

15) OPTION B --  bind to the LexA site

The “domain-swapping” experiment that grafts the Gal4 activation domain to the LexA DNA-binding domain generates a chimeric protein that will bind to the LexA site

LexA is a transcriptional repressor (EC 3.4. 21.88) that represses SOS response genes coding primarily for error-prone DNA polymerases, DNA repair enzymes and cell division inhibitors.

17)  complementary DNA (cDNA) is DNA synthesized from a single-stranded RNA (e.g., messenger RNA (mRNA) template in a reaction catalyzed by the enzyme reverse transcriptase

RNA is fundamentally much less stable than DNA.Therefore, the RNA needs to be reverse transcribed to DNA in order for it to be amplified.This is why cDNA is synthesized rather than studying mRNA.