Bootcamp Bio Question: cDNA and introns

[swindoll]

This question states that the eukaryotic gene WITH INTRONS has to be inserted into a plasmid. However, wouldn't the use of reverse transcriptase get rid of those introns? In that case, why is choice A not the correct answer?

I thought that cDNA will only contain exons (genes that were being expressed) since reverse transcriptase uses mRNA which contains info only for the exons and not introns... I hope I'm making sense here...

My question how can the use of cDNA be included in the researcher's procedure if he wants to a eukaryotic gene WITH INTRONS? Thanks!

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[emminent]

Alrighty so you misunderstood the question. It said that the researcher "WANTS" to insert a gene into the prokaryote. BUT the eukaryotic gene has INTRONS in it. So s/he didn't do anything yet but is planning on doing it and the question ask you that all the following choices are things s/he needs to do BUT what thing does s/he SHOULDN'T do.

Answer is C b/c you don't want to methylate the plasmid DNA b/c it'll make the DNA harder to read/transcribe. Methylation will cause tighter packing of the histones which prevents transcription.

The researcher would want to use reverse transcriptase b/c it'll not include the intron portion of the DNA. Once reverse transcription takes place to transcribe the DNA it will become a cDNA. Then you can use that which has no introns to insert into prokaryote.

 

[swindoll]

Ohh I see! Yeah, I read the first sentence as "researcher wants both introns and exons inserted into the plasmid", but now I see what you mean. And yes,choice C is something he definitely doesn't want to do because otherwise insulin won't be produced as bacterial genes won't be transcribing if they are methylated. Thank you so much! I now get it!

 

[goldenboy3.4]

Yes, methylation will cause the histones to be negatively charged. Since DNA is negatively charged, it will be attracted to the histones and will cause a tighter packing.

The opposite of this would be acetylation. This makes the histone groups to be more negatively charged. Thus, DNA will repel from it to make it more accessible.