DNA and RNA

• Nucleotides are made up of 3 components:

  • a pentose sugar
  • a phosphate group
  • a nitrogen containing organic base; C, A, T, G, U

  the 3 components join together by condensation reactions. the 3 components joined together form a mononucleotide
• 2 mononucleotides can be joined together to form a dinucleotide.

  There is a condensation reaction between the deoxyribose sugar on one nucleotide and the phosphate group of another.

  The bond that is formed is called a phosphodiester bond.
• If we join together multiple nucleotides we form a polynucleotide.
• RNA is a polymer made up of nucleotides.

  • it is a single strand
  • it has a ribose sugar attached to a phosphate group and a nucleotide
  • it only contains adenine, cytosine, guanine and uracil bases
  • there is no thymine in RNA
• 3 types of RNA

  • mRNA - messenger RNA that carries DNA code from nucleus to ribosome
  • tRNA - transfer RNA carries amino acids across the cytoplasm
  • rRNA - ribosomal RNA which makes up ribosomes
• what does DNA stand for

  Deoxyribonucleic acid
• DNA is made up of a deoxyribose sugar, a phosphate group and nucleotide bases:

  • the bases in DBA are adenine, cytosine, guanine and thymine
  • DNA is always made up of 2 strands and is usually much longer than RNA.
  • the pentose sugars and phosphates link by phosphodiester bonds to form the sugar-phosphate backbone of the DNA double helix.
• Stability of DNA-

  the phosphodiester backbone protects the more chemically reactive organic bases on the inside. this means we have to unwind the helix to get to the bases for DNA replication.

  Hydrogen bonds form bridges between the nucleotide bases who acts like a ladder along the backbone.

  As there are 3 hydrogen bonds between cytosine and guanine- the more C-G bonds that are presents, the more stable the helix is
• Function of DNA


  • very stable and normally passes from generations without change
  • 2 strands joined with hydrogen bonds allowing them to seperate during DNA replication and protein synthesis
  • large so can carry large amounts of genetic information
  • genetic information is protected inside double helix. protected from corruption by outside chemical and physical forces
  • base pairing means that DNA can replicate and transfer information such as mRNA
• Difference between DNA and RNA

  A) double stranded

  B) single stranded

  C) deoxyribose

  D) ribose

  E) A,T,G,C

  F) A,U,G,C

  G) Long

  H) short

  
• nucleotides

  A) phosphate

  B) base

  C) deoxyribose sugar

  
• what is a histone

  a protein
• how is DNA stored in the nucleus

  it is tightly wound up around a histone and coiled tightly until it forms a single chromosome
• How is DNA stored in a prokaryotic cell

  DNA double helix condenses into a circular chromosome and is coiled until it is supercoiled
• what is a gene

  sequence of DNA bases that codes for a polypeptide or functional RNA
• How are genes and amino acids related?

  Genes provide amino acids with information to assemble into specific proteins
• What are the 3 bases amino acids code for called

  triplets
• What are genes that dont code for polypeptides code for

  Functional RNA
• what is a complete set of genes in a cell called?

  genome
• What is the full range of proteins that the cell is able to produce called

  proteome
• does an intron code for amino acids


  no
• does an exon code for amino acids

  yes
• what is an allele

  gene that exists in more than one form