• 072920 77839
  • info@smartachievers.in
Menu
Back
  • JEE ADVANCE
  • JEE MAIN
  • NEET
  • BITSAT
  • CBSE BOARD
  • UP BOARD
  • CUET
JEE ADVANCE
  • CLASS XI - XII
  • CRASH COURSE
CRASH COURSE
JEE MAIN
  • CLASS XI - XII
  • CRASH COURSE
CRASH COURSE
NEET
  • CLASS XI - XII
  • CRASH COURSE
BITSAT
  • CLASS XI - XII
CBSE BOARD
  • CLASS IX
  • CLASS X
  • CLASS XI
  • CLASS XII
  • CLASS VI
  • CLASS VII
  • CLASS VIII
UP BOARD
  • CLASS IX
  • CLASS X
  • CLASS XI
  • CLASS XII
CUET
  • CRASH COURSE
Courses


Solution


Q.

In sea urchin DNA, which is double stranded, 17% of the bases were shown to be cytosine. The percentages of the other three bases expected to be present in this DNA are:   [2015]
1 G 17%, A 33%, T 33%  
2 G 8.5%, A 50%, T 24.5%  
3 G 34%, A 24.5%, T 24.5%  
4 G 17%, A 16.5%, T 32.5%  

Ans.

(1)

According to Chargaff’s rule, the amount of adenine is always equal to that of thymine and the amount of guanine is always equal to that of cytosine, i.e., A = T and G = C. Also, the purines and pyrimidines are always in equal amounts, i.e., A + G = T + C. Now, given dsDNA has 17% cytosine and hence guanine will be also 17%. So, A + T must be 66%, therefore, percentage of adenine or thymine would be 66 / 2 = 33%.