Unit 1

• Eukaryotes- DNA in nucleus, Linear Chromosomes packaged with protein Histone. DNA also found as circular chromosomes in membrane bound organelles.
• Prokaryotes- DNA found as single circular chromosomes in cytoplas. Plasmids are rags of extra DNA
• DNA- deoxyribonucleic acid
• Phosphate attatches to 5 of sugar.

  Base attatches to 1 of sugar.

  Two strands run parallel to eachother.
• Replication of DNA

  1. DNA is unwound and unzipped by breaking weak hydrogen bonds between bases.
  2. Primer is added as start point for replication.
  3. DNA Polymerase builds DNA strand by adding nucleotides to 3 end of growing strand.
  4. Primer replaced by DNA nucleotides and DNA strand winds up.
  5. Lagging strand is built in short sections due to directionality of DNA polymerase.
  6. Fragments on lagging strand are joined by ligase.
• PCR- Polymerase Chain Reaction

  Used to amplify DNA

  DNA replication in labs.

  1. Heat 95°, hydrogen bonds break.
  2. Cool 55°- allow primer to anneal. 1 primer for each end of target sequence.
  3. Heat 75°- heat tolerant DNA polymerase replicates section of DNA.
• Semi Conservative DNA Replicatio- each new DNA contains one oroginal strand and one new strand that is complementary to original.
• RNA- ribonucleic acid

  Adenine + Uracil
• mRNA- messenger RNA. Singke stranded RNA molecules carries complementary copy of gene to ribosome.
• tRNA- transfer RNA. Carries specific amino acid to ribosome. Anticodon lines with complementary mRNA to put amino acid in right place
• rRNA- ribosomal RNA. Makes up ribosome along with protein molecules.
• Transcription- DNA to mRNA.

  1. RNA polymerase unwinds and unzips gene.
  2. Reads DNA and builds a complementary strand of mRNA.
• RNA Splicing - Primary transcript to mature mRNA transcript.

  Introns removed from primary transcript and exons combined to produce mature transcript.

  Some exons can be treated as introns, allow us to produce multiple mature transcripts from one primary transcript - allows one gene to code for multiple proteins.
• Codon - sequence of three bases on mRNA that codes for an amino acid.
• Translation - the process of converting the information in a gene into a sequence of amino acids
• Translation:

  1. mRNA mature transcription leaves nucleus and binds with ribosome.
  2. tRNA have amino acid attatchment site and anticodon.
  3. tRNA brings specific amino acid to ribosome.
  4. Anticodon on tRNA lines up with complementary codon on mRNA bringing correct amino acid into line. START and STOP codons.
  5. Ribosome builds polypeptide chain by making peptide bonds between amino acids.
• Protein Folding: The process by which a polypeptide chain folds into a specific 3D shape.
• Primary structure - polypeptide, sequence of amino acid.
• Secondary Structure - initial folding, hydrogen bonds, neighbouring amino acids interact.
• Teritary - bonding between disparate amino acids, more complicated bonding.
• Quaterrary - different sub units connecting non protein component bind to protein
• Fibrous - long and thin e.g keratin and collagen.
• Globular - folded up to make specific shapes e.g amylase and insulin.
• Conjugated - globular protein with added non protein component e.g haemoglobin and chlorophyl.
• Mutation - change in DNA that can result in no protein or an altered protein being expressed.
• Frequency of mutations = no. Mutations / no. Gametes X100
• Single Gene Mutation - 1 base in the sequence is altered.

  • INSERTION - 1 base added
  • DELETION - 1 base removed

  These are frameshift mutations - all codons after point of mutation are changed. Different protein produced or non functioning protein produced.
• Substitution Mutation - 1 base in the sequence is replaced by another. Can cause different effects on the protein produced.

  • MISSENSE - causes codon to code for different amino acid.
  • NONSENSE - causes a STOP codon which causes a premature termination of the translation of the protein.
  • SILENT - change to the bases of the codon but still codes for the same amino acid.
• Splice Site Mutations - lead to some introns being retained and some exons removed from the mature transcript changing the protein produced.
• Chromosome mutations involve changes to the structure of one or more chromosomes in the genome.
• Deletion - one or more genes removed from the chromosome
• Duplication - one or more genes from a homologous chromosome are added to the chromosome
• Translocation - one or more genes from a non-homologous chromosome are added
• Inversion - order of a few genes in the chromosome is reversed
• Species - a group of organisms that share similar characteristics that can breed to produce fertile offspring
• Speciation - production of two or more seperate species from one ancestral population through the mechanism of evolution
• 1. Isolation - population is split into 2 sub populations by isolation barrier. geographical ( allopatric) ecological or behavioural ( sympatric )
• 2. Mutation - different mutations occur in each sub populatio. Some mutations provide an advantage to the organism while other provide a disadvantage depending on selection pressures.
• 3. Natural Selection - the non random in the frequency of DNA sequences that increase an organisms survival in a population.
• 4. Evolution - natural selection occurs over many generation. Genes are passed onto others either by vertical gene transfer or by horizontal gene transfer.