can you please explain both of these questions to me 1) you have a DNA detection

Question

can you please explain both of these questions to me

1) you have a DNA detection technique which allows you to visualize 10 nanograms of DNA. you know that the average molecular weight of a basepair is 660gm/mole. if a gene is exactly 4,000 basepair long, and is present only once in a bacterial genome ( 4 million basepairs), how many ugs of bacterial genomic DNA do you have to load onto the gel to be able to visualize the hybirdized DNA band?

2) you have a DNA detection technique which allows you to visualize 10 nanograms of DNA. you know that the average molecular weight of a basepair is 660gm/mole. if a gene is exactly 4,000 basepair long, and is present only once in a bacterial genome ( 4 million basepairs), how many DNA fragments of this gene do you need to have present to detect (those 10ng) of the gene-specific DNA fragment?

Explanation / Answer

1. if we compare your gene with the genome of the organism we will find that the gene is made up of 0.1% of total genome

4000/4000000 = 1/1000 = 0.1%

So if we load 1µg of genomic DNA then we will be able to visualise the DNA hybrid.

2. total Mw of gene will be 4000*2*660

4000= number of nucleotide in one strand and DNA has two strands so we need to multiply 4000*2

Mw = 5280000 gm

5280000 contains 6.023*1023 molecules of DNA

So 10 ng of DNA contain X number of molecules

5280000/10*10-9 = 6.023*1023/x

X = 6.023*1023*10*10-9/5280000

=* 1.14*109 molecules

1gm = 109 ng

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