DNA and Genes

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  • Created by: joe
  • Created on: 31-03-13 21:03

DNA contains genes which are instructions for proteins

  • Genes are sections of DNA. They are found on chromosomes.
  • Genes code for proteins (polypeptides) - they contain the instructions to make them.
  • Proteins are made from amino acids.
  • Different proteins have a different order and number of amino acids.
  • It's the order of nucleotide bases in a gene that determines the order of amino acids in a particular protein.
  • Each amino acid is coded for by a sequence of three bases (called a triplet) in a gene.
  • Different sequences of bases code for different amino acids.
  • The base sequence of a gene determines the amino acid sequence in a polypeptide)

Not all DNA in eukaryotic cells codes for proteins

  • Genes in eukaryotic DNA contain sections that don't code for amino acids.
  • These sections of DNA are called introns (all the bits that do code for amino acids are called exons).
  • Introns are removed during protein synthesis. Their purpose isn't known for sure.
  • Eukaryotic DNA also contains regions of multiple repeats outside of genes.
  • These are DNA sequences that repeat over and over (e.g. ccttccttcctt)
  • These areas don't code for amino acids either.

The nature and development of organisms is determined by genes

  • Enzymes speed up most of our metabolic pathways - chemical reactions that occur in the…


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