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CBSE - X - Biology - How Do Organisms Reproduce?

Give a brief account on DNA?

Asked by Praveen Kumar 30th September 2013, 12:08 AM
Answered by Expert


DNA: Deoxyribonucleic Acid

The three-dimensional structure of DNA was discovered in 1953 by Watson and Crick for which work they won a Nobel Prize. The main features of the structure are:

  • DNA is double-stranded, so there are two polynucleotide stands alongside each other.
  • Each single strand of DNA is made of repeating units of nucleotides.

  • Single nucleotide is made up of: pentose sugar (deoxyribose sugar), phosphate group and nitrogenous bases.
  • The strands are complementary and antiparallel i.e. they run in opposite directions thus 5' to 3' is parallel to 3' to 5'.
  • The two strands are wound round each other to form a double helix.
  • The two strands are joined together by hydrogen bonds between the nitrogenous bases.
  • The bases therefore form base pairs, which are like rungs of a ladder.
  • The base pairs are specific. A only binds to T by a double bond of hydrogen) and C only binds to G by triple bond of hydrogen.
  • These are called complementary base pairs. This means that whatever the sequence of bases along one strand, the sequence of bases on the other stand must be complementary to it.
Answered by Expert 30th September 2013, 8:22 AM

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