You are working in a lab that just identified a human protein called p221a thoug

Question

You are working in a lab that just identified a human protein called p221a thought to be involved in cell cycle regulation and cancer. You would like to identify this gene in mice (Mus musculus) so you can study the gene in a model organism.

Here are two definitions that will be helpful for this problem.
consensus sequence: a DNA or protein sequence that is conserved in many species and is likely important evolutionarily.
reverse-translation: the process of using the genetic code to deduce the DNA sequence (codons) that encodes the amino acid sequence of a protein.

PART A: Your plan is to use colony hybridization to identify the mouse p221a gene from a cDNA library. However, you do not know the sequence of the mouse p221a gene.

How would you design a probe that would hybridize to this gene?

A) Design a probe by reverse-translating a consensus sequence from a comparison of the p221a amino acid sequence in other species.

B) Design a probe that recognizes repetitive sequences that are found throughout the mouse genome.

C) Design a probe that recognizes consensus sequences in mouse promoter regions.

D) Design a probe that hybridizes to a consensus sequence from a comparison of the DNA sequence of the p221a gene in other species.

E) Design a poly-T probe that will bind to the poly-A tail of mRNAs.

PART B: This image shows an amino acid sequence alignment of the p221a protein in several mammalian species. Four regions (A-D) are indicated below the image.

Which would be the best region of the protein to use to design a reverse-translated probe for a colony hybridization experiment?

A) region A

B) region B

C) region C

D) region D

PART C: Now you would like to use the p221a probe in a colony hybridization experiment using a mouse cDNA library. Put the steps of the colony hybridization experiment in order in the flow chart below.

PART D: After completing the colony hybridization experiment, you see two black spots on the X-ray film. What do the black spots represent? (SELECT ALL THAT APPLY)

A) locations where the radioactive probe hybridized to DNA on the membrane

B) colonies that express the mouse p221a protein

C) colonies that contain DNA that is complimentary to the radioactive probe

D) colonies that contain the mouse cDNA library

E) colonies that contain the mouse p221a cDNA

Explanation / Answer

A) option A: Design a probe by reverse-translating a consensus sequence from a comparison of the p221a amino acid sequence in other species.

B) option C: region C

C) The correct order is 1,2,6,4,5,7,3

C) Options A, C, and E

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