You have various samples of purified DNA each eluted in a fi

You have various samples of purified DNA (each eluted in a final volume of 50 mu l) collected from a sexual assault case and you need to develop STR profiles from each. Your lab procedure calls for PCR amplification of a total of 0.5 ng of DNA in 5 mu l. Assume that you should make at least 100 nl of each dilution, you are using 1.5ml tubes, and you may use a P50, P200, and/or P1000. DNA concentrations are listed below for each of the samples. a. How would you dilute these samples?

Solution

Final concentration of DNA should be 0.5 ng in 5 l or 0.1ng in 1 l. You need to have 100 l solution, so final concentration of DNA should be 10 ng/100 l

Try to convert all the concentrations in ng/ l

Specimen

Concentration of DNA

Concentration of DNA (ng/l)

Victim Known

0.85 g/l

850 ng/l

Suspect Known

1.10 g/l

1100 ng/l

Elimination standard  

2.5 g/l

2500 ng/l

Thigh swab  

0.93 ng/l

0.93 ng/l

Vaginal swab

17.46 ng/l

17.46 ng/l

Sheet stain  

6.84 ng/l

6.84 ng/l

(1)Victim Known

850 ng/l, now add 200 l of diluent to it, so that it becomes 850 ng/200 l.

You need only 10 ng

If 850 ng/ l is present in 200 l, then 10ng is present in how many l

C1V1=C2V2

V1=10ngx200 l/850ng=2.35 l

Try to pipette out 2.35 l from the above 200 l of solution and make this upto 100 l by adding 97.65 diluent

(2)Suspect Known

1100 ng/l, now add 200 l of diluent to it, so that it becomes 1100 ng/200 l.

You need only 10 ng

If 1100ng/ l is present in 200 l, then 10ng is present in how many l

C1V1=C2V2

V1=10ngx200 l/1100ng=1.82 l

Try to pipette out 1.82 l from the above 200 l of solution and make this upto 100 l by adding 98.18 diluent

(3) Elimination standard  

2500 ng/l, now add 500 l of diluent to it, so that it becomes 2500 ng/500 l.

You need only 10 ng

If 2500 ng/ l is present in 500 l, then 10ng is present in how many l

C1V1=C2V2

V1=10ngx500 l/2500 ng=2 l

Try to pipette out 2 l from the above 500 l of solution and make this upto 100 l by adding 98 diluent

(4)Thigh swab  

0.93 ng/l, now add 5 l of diluent to it, so that it becomes 0.93 ng/5 l.

You need only 10 ng

If 0.93 ng/ l is present in 5 l, then 10ng is present in how many l

C1V1=C2V2

V1=10ngx5 l/0.93 ng=53.76 l

Try to pipette out 53.76 l from the above 5 l of solution and make this upto 100 l by adding 46.24 diluent

(5)Vaginal swab

17.46 ng/l, now add 5 l of diluent to it, so that it becomes 17.4 ng/5 l.

You need only 10 ng

If 2500 ng/ l is present in 5 l, then 10ng is present in how many l

C1V1=C2V2

V1==10ngx5 l/17.46   ng=2.86 l

Try to pipette out 2.86 l from the above 5 l of solution and make this upto 100 l by adding 97.14 diluent

(6)Sheet stain  

6.84   ng/l, now add 5 l of diluent to it, so that it becomes 6.84 ng/5 l.

You need only 10 ng

If 6.84 ng/ l is present in 5 l, then 10ng is present in how many l

C1V1=C2V2

V1=10ngx5 l/6.84 ng=7.31 l

Try to pipette out 2.86 l from the above 5 l of solution and make this up to 100 l by adding 92.7 diluent

Specimen	Concentration of DNA	Concentration of DNA (ng/l)
Victim Known	0.85 g/l	850 ng/l
Suspect Known	1.10 g/l	1100 ng/l
Elimination standard	2.5 g/l	2500 ng/l
Thigh swab	0.93 ng/l	0.93 ng/l
Vaginal swab	17.46 ng/l	17.46 ng/l
Sheet stain	6.84 ng/l	6.84 ng/l