You are a research assistant in a lab that studies nucleic a

You are a research assistant in a lab that studies nucleic acids. Your advisor gave you four tubes for analysis. Each of these tubes differs in its contents by the source of its nucleic acids: mouse cytoplasm (single-stranded RNA), yeast nuclei (double-stranded DNA), rotavirus (double-stranded RNA), and parvovirus (single-stranded DNA). The approximate nucleotide base composition of each sample is given in the table below.   Which tube MOST likely contains a rotavirus?

Tube

A

C

U

T

G

1

32

17

0

32

19

2

34

16

15

0

35

3

30

21

0

26

23

4

33

16

34

0

17

Solution

ANS: Tube no. 4 most likely to contain rotavirus. As rotavirus is a duble-stranded RNA virus, it should contain A, U, G and C. Tube 2 and tube 4 is having this in common. Being double-stranded the no. of ourines should be equal to no. pyramidines, ie. A=U and C=G, the same pattern is seen in tube 4 but not in tube 2. So the correct ans. is tube 4.