Cell/Molecular Review Questions, Please Help?

[Didact1]

Hello I would appreciate some assistance with the following review questions as my exam is coming up in a few weeks I'm just revising my content, however, there seems to be a limited range of practice questions and when it comes to these I seem to struggle, so would appreciate some explanations/walkthroughs as to how to do them so I may learn.

 

ESTIMATING GENE NUMBERS

Approximately 1% of the human genome consists of protein-coding sequences (exons). A diploid somatic human cell contains 5 picograms/pg of DNA and rapidly growing E.coli cells contain on average four genomes giving a total of 0.017pg of DNA. Assuming that the sequences within the E.coli DNA codes for protein and that the average size of proteins is similar in humans and E.coli, how many more proteins could theoretically be expressed by the haploid human genome than by the haploid E.coli genome?

LIGATION THEORY

A 100bp fragment is to be cloned into the EcoRI site of pBR328 (4.9 Kb) in order to detect successful insertions using blue/white selection. Given that there are 50 nanograms of EcoRI digested pBR328, on the basis of the optimal ratio of insert: vector for ligations, how much insert would be added to the 50ng of EcoRI digested pBR328 to ensure the best possible chance of successful ligation? (MW dsDNA = 660; MW ssDNA = 330)


Again would appreciate some feedback/walkthrough of these questions as I'm currently doing practice questions.

Cheers, Didact1

 

[LauraW]

Hey! I don't quite understand the wording of the first question but I think I get the second question.

 

Apparently, the optimal vector:insert ratio is 1:3.

 

Your answer can be determined by the following equation:

ng of vector X kb size of insert insert

------------------------------------------ x molar ratio of -------------

kb size of vector vector

 

Plug in your known values:

Kb size of vector: 4.9

Kb of insert: 0.1 (100b not Kb!)

ng of vector : 50

molar ratio of insert: 3

molar ratio of vector: 1

 

Throw these into that equation and bobs your uncle!

(not sure why they gave you the MW of dsDNA or ssDNA)

 

I hope this is right.