10. (15 points) You have an oligonucleotide probe that hybridizes to part of gen

Question

10. (15 points) You have an oligonucleotide probe that hybridizes to part of gene A from a eukaryotic cell. Indicate whether a cDNA library or a genomic DNA library will be more appropriate for use in the following applications. A You want to study the promoter of gene A. B. Gene A encodes a tRNA and you wish to isolate a piece of DNA containing the C You discover that gene A is alternatively spliced and you want to see which DYou want to find both gene A and the genes located near gene A on the EYou want to express gene A in bacteria to produce lots of protein A full-length sequence of the tRNA. predicted alternative splice products the cell actually produces chromosome

Explanation / Answer

cDNA library is made from reverse transcribing RNA where as a genomic library is made by PCR amplifying specific regions from genomic region.

A) Promoter sequecne are present on the DNA and provide the signal for RNA transcription and hence are absent on the RNA.

Hence to study the promoter sequnce we will need the genomic library.

B) Gene A encodes tRNA and to isolate the full length sequence of the tRNA we need to again use the genomic library.

we cannot use the cDNA library becuase it contain the tRNA sequence after intron splicing. Hence we wont get the full sequence that is on the genome.

C) Alternate spliced forms can only be studied at the RNA level. Only after the complete RNA is synthesised, splicing machniery splice the RNA into different forms.

Hence to study this we need a library made from RNA and hence we use teh cDNA library

D)To know the genes in the vicinity of Gene A, we use genomic library.

E) To express the protein in E. coli, we need the exact sequence of gene A from the genome. and hence we use the genomic library

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