Question

Which is used to select genes from the genomic library?
(A)Cloning vectors
(B)DNA probes
(C)Gene targets
(D)Restriction enzyme

Answer 1

Hint:A genomic library contains all the sequences present in the genome of an organism (apart from any sequences, such as telomeres which cannot be readily cloned). It is a collection of cloned, restriction enzyme digested DNA fragments containing at least one copy of every DNA sequence in a genome.

Complete answer:
Genomic library is a complete collection of cloned DNA fragments which comprises the entire genome of an organism. Molecular probes are small DNA segments that are used to detect the presence of complementary sequences in nucleic acid samples in genomic libraries. And these are usually formed of 200-500 nucleotide sequences.

 These segments or probes are labelled either with radioactive or with nonradioactive compounds. Probes with DNA sequence complementary to the gene to be isolated are used. They bind with the desired gene, making it visible and help in isolating it from the library.

A genomic DNA library is a collection of DNA fragments that make up the full length genome of an organism. A genomic library is created by isolating DNA from cells and then amplifying it using DNA cloning technology. DNA probes are stretches of single-stranded DNA used to detect the presence of complementary nucleotide sequences by hybridization. Genomic library comprises a large number of genes in the form of different nucleotide sequences of DNA fragments and they can be selected with the help of DNA probes.

Thus, the correct answer is option (B).

Note:DNA probe direct hybridization assays and generally follow the two basic formats. In this format, direct colony hybridization involves the impression transfer of bacterial cells as primary colony isolates onto a nylon or nitrocellulose membrane.