Q) Describe the differences between a gDNA and a cDNA library
Main points | |
Key idea: | What is a genomic DNA vs cDNA library |
· cDNA library – contains only coding seq of genes · Ref to genes that are expressed in a particular cell type or tissue at a particular stage of dev of organism · gDNA library - comprises of all DNA seq (including coding seq + non-coding seq e.g. regulatory seq, repetitive DNA) · Ref to seq remains the same regardless of type of cells or tissue used and stage of dev | |
Key idea: | Size and composition of the libraries |
· cDNA library – smaller than gDNA library (of the same organism) · Reason: expressed gene seq only make up a small % of total genomic DNA | |
Key idea: | Construction of the libraries – starting material |
· gDNA library – genomic DNA · cDNA library – messenger RNA | |
Key idea: | Construction of the libraries – enzymes involved |
· gDNA library – includes restriction enzymes, DNA ligase and DNA polymerase · cDNA library – same as in gDNA library but also requires reverse transcriptase to syn cDNA fr mRNA template | |
Key idea: | Isolation of functional protein coded by eukaryotic gene from E.coli |
· gDNA library – Unlikely to isolate functional protein expressed by euk gene isolated from the gDNA library using bacteria cells · Reason: pre-mRNA is not processed to form mature mRNA in prokaryotes · Details: introns of mRNA not removed, would give rise to additional aa in polypep after translation · cDNA library – Possible · Reason: gene fr cDNA library contains only coding seq; after transcription, no intron seq in mRNA, functional protein can be produced using bacteria | |
Comments: (i) Visualize the answer with the aid of a labelled diagram. (ii) Verbalize the answer + write down the main points w/o referring to the answer (use abbreviations) (iii) Read again within the next 24h & once more within 72h (do not spend more than 10min) (iv) Remember to use ‘comparative’ terms e.g. whereas, unlike, etc (v) Refer to previous post for a more comprehensive list of enzymes for the synthesis of cDNA library | |
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