Bio- Gene Expression

• DNA is a molecule containing the genetic material that organises all cell processes. It forms a double helix and is made up of repeating nucleotides. The DNA bases are adenine, thymine, guanine and cytosine.
• RNA is a small single-stranded molecule that contains genetic information. In an RNA nucleotide, the sugar is ribose and the bases are adenine, uracil, guanine and cytosine.
• Protein synthesis is when a protein is made using the instructions encoded in DNA of a gene.
• Transcription is when an mRNA strand that codes for a polypeptide is formed using DNA as a template.
• Mutagen


  An environmental agent that causes a change to the DNA base sequence

  
• Examples of mutagens


  UV radiation, x rays, cigarette smoke

  
• Mutation


  A permanent change in the DNA base sequence
• Point Mutation


  A gene mutation in which a single base pair in DNA has been changed

  
• Substitution


  A mutation in which a nucleotide is replaced with a different nucleotide

  
• Nonsense mutation


  A mutation that codes for a stop codon, resulting in a shorter and usually nonfunctional protein.

  
• Missense mutation


  A substitution mutation that results in a codon that codes for a different amino acid.

  
• Effect of a missense mutation on the protein


  A change in amino acid will result in the protein folding differently which will affect its shape and therefore function.
• Silent mutation


  A substitution mutation that codes for the same amino acid because of degeneracy of the code

  
• Effect of a silent mutation on the protein


  No effect because the length and order of bases is exactly the same, and the final protein folds correctly and therefore functions correctly.
• Deletion mutation


  A loss of a nucleotide in the DNA sequence

  
• Insertion mutation


  An addition of a nucleotide in the DNA sequence

  
• Frameshift mutation


  an insertion or deletion in the DNA base sequence that changes the reading frame

  
• Effect on frameshift mutations on the protein

  Has a major effect because the amino acid sequence from the point of the mutation onwards will be different causing

  the protein to fold incorrectly therefore negatively effecting the function of the protein.
• Protein


  A polymer that is made of one or more polypeptide chains folded into a functional 3D shape
• Protein Synthesis


  the formation of proteins by using information contained in DNA
• Amino Acid


  Building blocks of protein
• Polypeptide


  A polymer of many amino acids linked together by peptide bonds.
• Peptide bond


  Bond that joins two neighbouring amino acids together in a polypeptide chain
• Triplet


  A sequence of three consecutive bases in DNA that codes for an amino acid
• Ribosome


  Organelle where translation takes place
• DNA


  Large molecule in the nucleus made of nucleotides that carries the genetic code
• Gene


  A section of DNA that codes for the production of one polypeptide chain
• Transcription


  The process of creating a strand of mRNA from a template strand of DNA
• Promoter region


  region of DNA that RNA polymerase attaches to begin transcription.
• Terminator region


  region on gene that marks the end of transcription
• RNA polymerase


  enzyme that links together the growing chain of RNA nucleotides during transcription using a DNA strand as a template
• mRNA


  messenger RNA; type of RNA that carries instructions from DNA in the nucleus to the ribosome
• Template strand


  the strand of DNA that is used as a template to make mRNA using complementary base pairing
• Coding Strand


  the strand of DNA that is not used for transcription and is identical in sequence to mRNA, except it contains uracil instead of thymine
• Translation


  Process of amino acids joining together in correct sequence using mRNA as a template
• tRNA


  transfer RNA; type of RNA that carries amino acids to the ribosome
• rRNA


  ribosomal RNA; type of RNA that makes up part of the ribosome
• Codon


  A sequence of three consecutive bases in mRNA
• Anticodon


  A sequence of three consecutive bases in tRNA
• Degeneracy


  most amino acids are encoded by several codons