# calculation help - (Mar/03/2008 )

Hi there,

Ive got a lab tomorrow and as Im going over the instructions something is confusing...

so we have to create a dilution series from a known stock concentration of DNA..

so to tube (1) it says to add 10u 1 of stock DNA (100ng/uL) to this tube...what i am confused about is when it says 10u (does it actually mean 10uL and is it just a printing error?)...and is the conc. of the DNA 100ng/uL meaning in 1uL of solution there is 100ng of DNA ...

ok then it says to another tube (A) add 2u 1 stock of DNA and 18uL of water to this tube
then to tube 2 add 10u 1 from tube A
to tube B add 2u 1 from tube A and 18u 1 of sterile water to this tube
to tube 3 add 10u 1 from tube B
to tube C add 2u 1 from tube B and 18u 1 water to this tube
to tube 4 add 10u 1 from tube C

okkk so i get all thaaat (assuming that the printing error is correct from wat i wrote above)??? now I have to calculate the conc. in each of the tubes 1-4...and im not sure if im doing it right? can someone please tell me if ive done this correctly?

im thinking this how you do it. (for tube 2 which is essentially tube A)---10uL*100ng/uL divided by 12uL=83.33ng/uL

hence tube 3 would be 83.33*10/12???

Cheers,
biology_06er

-biology_06er-

QUOTE (biology_06er @ Mar 3 2008, 07:47 PM)
Hi there,

Ive got a lab tomorrow and as Im going over the instructions something is confusing...

so we have to create a dilution series from a known stock concentration of DNA..

so to tube (1) it says to add 10u 1 of stock DNA (100ng/uL) to this tube...what i am confused about is when it says 10u (does it actually mean 10uL and is it just a printing error?)...and is the conc. of the DNA 100ng/uL meaning in 1uL of solution there is 100ng of DNA ...

ok then it says to another tube (A) add 2u 1 stock of DNA and 18uL of water to this tube
then to tube 2 add 10u 1 from tube A
to tube B add 2u 1 from tube A and 18u 1 of sterile water to this tube
to tube 3 add 10u 1 from tube B
to tube C add 2u 1 from tube B and 18u 1 water to this tube
to tube 4 add 10u 1 from tube C

okkk so i get all thaaat (assuming that the printing error is correct from wat i wrote above)??? now I have to calculate the conc. in each of the tubes 1-4...and im not sure if im doing it right? can someone please tell me if ive done this correctly?

im thinking this how you do it. (for tube 2 which is essentially tube A)---10uL*100ng/uL divided by 12uL=83.33ng/uL

hence tube 3 would be 83.33*10/12???

Cheers,
biology_06er

first things first. there is a typo in the presentation. the typist separated the u from the l in ul (ie u 1) using the 1 key for the l key (the opposite used to be done when using a typewriter without a 1 key).

now for the dilution series...

the stock (tube 1) contains 100ng in each ul (as you correctly assume).

tube a: take 2ul stock and add 18ul water is a 10x dilution (2ul in a final volume of 20ul). this gives you 10ng/ul. tube 2 is this concentration (you take 10ul from tube a, concentration doesn't change but you have the 10ul that you need for the standard curve)

tube b: take 2ul of tube a and add 18ul water...

i would guess that you can figure the rest.

-mdfenko-