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.

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.

Answer 1

The best method to design a probe to identify the mouse p221a gene from a cDNA library is to use reverse-translation of a consensus sequence identified from comparing the p221a amino acid sequences in various species, enabling the creation of a probe set that can hybridize to the gene in question.

Step-by-step explanation:

To identify the mouse p221a gene from a cDNA library, the best strategy would be A) Design a probe by reverse-translating a consensus sequence from a comparison of the p221a amino acid sequence in other species. This involves comparing the amino acid sequence of the human p221a protein with those of other species to identify a conserved consensus sequence.

Once a consensus sequence is identified, it can be reverse-translated into all possible nucleotide sequences that could code for it, considering the degeneracy of the genetic code. This provides a set of probes that can be used to screen a cDNA library constructed from mRNA, which represents only the genes being expressed in a particular tissue or organism, without the non-coding regions and introns found in genomic DNA.