DNA and RNA

• DNA and RNA function

  • DNA and RNA are both types of nucleic acid. They're found in all living cells and they both carry information
  • Your DNA is used to store your genetic information - that's all the instructions needed to grow and develop
  • RNA is similar in structure to DNA. One of its main functions is to transfer genetic information from the DNA to the ribosomes
  • Ribosomes are made from RNA and proteins
• Polypeptide structure:

  • Many nucleotides join together to form polynucleotide strands
  • The nucleotides join up via a condensation reaction between the phosphate group of one nucleotide and the sugar of another
  • This forms a phosphodiester bond
  • The chain of phosphates and sugars is known as the sugar-phosphate backbone
• Nucleotide structure:

  • Molecules or DNA and RNA are polymers of nucleotides.
  • A nucleotide is a type of biological molecule which is made from three different components: a pentose sugar, a nitrogen-containing organic base, and a phosphate group
  • Nucleotides are really important as they are the monomers that make up DNA and RNA
• DNA structure

  • DNA has a double helix structure
  • This means that a DNA molecule is formed from two separate strands which wind around each other to form a spiral
  • The strands are polynucleotide
  • They're made up of lots of nucleotides joined together in a long chain
  • DNA molecules are really long and are coiled.up very tightly, so a lot of genetic information can fit into a small space in the cell nucleus
• DNA nucleotide structure:

  • A DNA nucleotide is made from a phosphate group, the pentose sugar deoxyribose and a nitrogen-containing organic base
  • Each DNA nucleotide has the same sugar and phosphate.
  • The base of each nucleotide can vary into 4 possible bases: adenine, thymine, cytosine, guanine
• Complementary base pairing:

  • Two DNA polynucleotide strands join together by hydrogen bonds between the bases
  • Each base can only join with one particular partner - this is called complementary base pairing
  • Adenine always pairs with thymine and guanine always pairs with cytosine
  • Two hydrogen bonds form between A and T, and three hydrogen bonds form between C and G
  • The two polynucleotide strands are antiparallel - they run in opposite directions. Two antiparallel strands twist to form a DNA double helix
• RNA structure

  • The sugar in RNA nucleotides is a ribose sugar - still a pentose sugar
  • Uracil replaces thymine as a base. Uracil always pairs with adenine in RNA
  • The nucleotides form a single polynucleotide strand
  • RNA strands are much shorter than most DNA polynucleotides
• DNA was first observed in the 1800s, but lots of scientists at the time doubted that it could carry the genetic code because it has a relatively simple chemical composition. Some argued that genetic information must be carried by proteins — which are much more chemically varied.

  By 1953, experiments had shown that DNA was the carrier of the genetic code. This was also the year in which the double helix structure, which helps DNA to carry out its function, was determined by scientists James Watson and Francis Crick