c13

• Polynucleotides


  A chain of repeating monomers called nucleotides

  
• Nucleotide


  A pentose sugar, a phosphate group, and a nitrogenous base

  
• Nucleoside


  Pentose sugar + nitrogenous base
• Nucleotide


  Nucleoside + phosphate group
• Base pairing rule


  A=T, C=G
• Proteins


  • Long chain of amino acids (aa), linked to each other by peptide bonds
  • Made from 20 amino acids, each with specific properties due to its side chains
  • Essential amino acids (9), non-essential aa (5), conditional aa (6)
  • Each amino acid has an amine group, a carboxyl group, a hydrogen atom and a side chain (R)
  • Some side chains are non-polar and hydrophobic, others are hydrophilic, or positively or negatively charged
  • Dipeptide - 2 aa, Oligopeptide - 3-10 aa, Polypeptide- 10 or more aa, Protein - 50 or more aa

  
• Protein structure

  • Primary - sequence of amino acids
  • Secondary - proteins fold to form alpha helices and beta pleated sheets
  • Tertiary - 3D shape determined by folding of secondary structure
  • Quaternary - combined 3D structure of two or more polypeptide chains

  
• Types of proteins


  • Fibrous proteins - simple, elongated polypeptide chains, insoluble, structural, less sensitive to changes in temp, ph
  • Globular proteins - polypeptide chain folds up into a compact shape, water soluble, mobile, chemically active, sensitive to changes in temp, ph

  
• Protein synthesis


  1. Transcription - DNA to mRNA in nucleus

  2. Translation - mRNA to protein in cytoplasm
• Proteome


  All the proteins that a cell makes, proteomics is the study of the proteins in a cell
• Gene


  A segment of DNA that specifies the structure of a protein

  
• Genetic code


  Specific arrangement of nucleotides in DNA and RNA that determine amino acid sequence of a specific protein

  
• Gene expression


  Production of proteins from the information stored in DNA
• Central dogma


  Directional flow of information from DNA to RNA to protein
• Transcription


  DNA uncoils and unzips, RNA polymerase produces mRNA, mRNA exits nucleus
• Translation


  mRNA is converted into a protein
• Tides in DNA and RNA


  Determine amino acid sequence of a specific protein

  
• Central dogma


  Directional flow of information from DNA →RNA →protein
• Gene expression


  1. Transcription

  2. Translation
• Transcription


  1. DNA uncoils and unzips

  2. RNA polymerase produces messenger RNA (mRNA)

  3. mRNA exits nucleus through nuclear pores
• Transcription


  • Initiated by transcription factors that recruit RNA polymerase enzyme
  • DNA has coding strand and template strand
  • RNA polymerase binds at a promoter region and catalyses formation of mRNA chain following complementary base pairing rules
  • Transcription ends at a terminator sequence
• Translation


  1. mRNA carries genetic information to ribosomes

  2. Ribosome reads mRNA sequence in lots of three nucleotides (codons)

  3. Each codon codes for a specific amino acid

  4. tRNA with complementary anticodon binds to each codon and carries the specified amino acid

  5. Amino acids are joined by peptide bonds in the sequence specified by the mRNA to make a protein

  
• Codons


  Nucleotide triplets in mRNA that code for specific amino acids

  
• There are 64 possible codons in mRNA and only 20 naturally occurring amino acids
• Stop codons


  UAG, UAA, UGA - codons that do not code for an amino acid but signal termination of the peptide chain
• Post-translational modification


  Chemical modification of a protein following translation, can change or extend its functions
• The process by which DNA is copied to RNA is called transcription
• The process by which RNA is used to produce proteins is called translation
• Somatic cell


  Biological cell forming the body of a multicellular organism, most cells, 46 chromosomes (diploid number), undergoes mitosis
• Germ cell


  Cells that give rise to gametes, located in the gonads, undergoes meiosis
• Gamete


  Cells that fuse during sexual reproduction, sperm or egg, 23 chromosomes (haploid number)
• Cell life cycle


  1. Interphase

  2. Mitosis

  3. Cytokinesis
• Chromatin


  DNA complexed with proteins (histones), condenses into pairs of chromatids called chromosomes during cell division

  
• Homologous chromosomes


  Pairs of chromosomes where one is from the father and the other is from the mother
• Locus


  The location of a gene on a chromosome

  
• Allele


  Different forms of the same gene
• DNA replication


  During interphase, each chromosome becomes doubled, consisting of 2 identical sister chromatids connected by a centromere

  
• Mitosis


  1. Prophase

  2. Metaphase

  3. Anaphase

  4. Telophase

  5. Cytokinesis
• Mitosis


  • Produces 2 identical daughter cells
  • Centrioles migrate to ends of cell and organize spindle fibers
• Meiosis


  1. DNA replication followed by two cell divisions

  specialised for sexual reproduction

  DNA replication by two cell divisions

  2. Produces 4 genetically different daughter cells (gametes)