Protein synthesis HT: Inheritance, variation and evolution: Biology: GCSE (9:1)

• DNA


  Chemical molecules found in every living organism that hold instructions for growth and development

  
• Gene


  A small section of DNA that controls a specific characteristic by coding for a specific protein

  
• Nucleotide


  A small structural unit of DNA, composed of a common sugar and phosphate group with one of four different bases attached to the sugar

  
• Bases


  A specific organic section of a nucleotide that contains nitrogen, there are four different types of bases in a DNA polymer

  
• C, G, A and T


  The letters that represent the four different types of bases found on a strand of DNA

  
• Repeating nucleotides

  The DNA polymer is made up of repeating nucleotide units with different arrangements of the bases C, G, A and T

  
• Complementary base pairs


  The bases found on one strand of DNA must pair with specific bases on the other DNA strand, so that the strands can be held together

  
• Complementary strands


  A DNA molecule is made of two strands that are held together by the bonds between complementary base pairs

  
• C

  A base that is complementary to G, it will not pair up with A or T on the complementary strand

  
• A

  A base that is complementary to T, it will not pair up with a C or G on the complementary strand

  
• Sequence of three bases

  The genetic code for an amino acid also called a codon or triplet, this arrangement of three bases leads to the formation of one specific amino acid

  
• Amino acids

  The building blocks of proteins, the sequence of amino acids determines the shape and function of the overall protein

  
• Proteins

  Building blocks of cells and tissues, made up by a specific order of amino acids which in turn is coded for by a specific sequence of DNA

  
• First stage of protein synthesis

  Known as transcription, a single strand of DNA is unzipped from the double helix by enzymes and copied by a messenger molecule

  
• Messenger molecule


  Also called messenger RNA or mRNA, the messenger molecule is a copy of a single DNA strand that is small enough to leave the nucleus

  
• Messenger molecule structure

  The messenger molecule has a slightly different structure than DNA, it is single-stranded and has a base called U instead of T

  
• Second stage of protein synthesis

  Known as translation, the messenger molecule moves to a ribosome in the cytoplasm and is translated into amino acids by carrier molecules

  
• Ribosome

  The site of protein synthesis, where carrier molecules bring specific amino acids to form a chain according to the messenger molecule sequence

  
• Carrier molecule


  Also called transfer RNA or tRNA, each carrier molecule reads a triplet of bases on the messenger molecule and translates it into an amino acid

  
• Carrier molecule structure


  Each carrier molecule is attached to an amino acid and contains three bases that are complementary to a triplet on the messenger molecule

  
• Protein chain


  When a chain of amino acids is completed it folds up to form a specific shape, enabling proteins to do their jobs as enzymes, hormones or structural collagen