DNA

• Scientists

  Watson and Crick
• DNA stands for

  Deoxyribonucleic acid
• 2 non nuclear locations of DNA

  1. Mitochondria
  2. Chloroplast
• DNA shape

  Double helix
• Basic unit of DNA

  Nucleotide
• Nucleotides are made up of

  • Phosphate group
  • Sugar
  • Nitrogen base
• Ribose= sugar for RNA, Deoxyribose= sugar for DNA
• 2 groups for nitrogen based

  • Purines
  • Pyrimidines
• Purines

  • Adenine
  • Guanine
• Pyrimidines

  • Thymine
  • Cytosine
• Uracil replaces thymine in RNA
• Complementary pairs

  A - T

  G - C
• RNA polymerase function

  Helps form mRNA
• DNA replication

  A double stranded DNA molecule is copied to produce two identical DNA molecules
• When and where does DNA replication take place

  During interphase in the nucleus
• Steps of DNA replication

  1. UNWINDING: original DNA double helix unwinds
  2. SEPARATING: An enzyme helicase breaks the bonds between the base pairs and the DNA strands separate
  3. JOINING OF THE NEW BASES: DNA bases enter from the cytoplasm into the nucleus. New DNA bases join with the original complimentary DNA bases. The enzyme DNA polymerase carries this process out
  4. REWINDING: Each new strand is half new DNA and half old DNA. Identical to original strand. Double helix rewinds to form 2 identical copies
• Significance of DNA replication

  The same genetic material can be passed from one generation to the next
• Heredity

  Is the passing on of characteristics from one generation to the next -genetic inheritance
• Gene

  A section of DNA that codes for a protein. Many of these proteins are enzymes and therefore control the cell. Genes are units of heredity
• Gene expression

  The process by which the code in DNA is used to make a protein. It is the expression of genes that produce the characteristics that are inherited
• Characteristics= heredity + environment
• 2 chemical components/constituents of chromosomes

  DNA (40%) and protein (60%)
• The bits that aren't genes on a chromosome are

  Non coding DNA/junk DNA
• Non coding/junk DNA

  Does not cause production of amino acids/protein
• Coding DNA

  Codes for the production of amino acids by a sequence of 3 bases called a codon or triplet
• How many types of amino acids are there

  20
• 1 amino acid is made up of

  3 consecutive bases (known as a triplet or codon)
• DNA profiling

  A method of making a unique pattern of bands from the DNA of a person, which can be then used to distinguish that DNA from other DNA
• DNA profiling stages

  • Isolation of DNA from the cell
  • Cutting - DNA cut into fragments of different lengths using restriction enzymes
  • Separation - Separated by a process called gel electrophoresis based on different sized fragments
  • Analyse and compare patterns. 2 DNA profiles will never be the same except identical twins (same genes)
• Applications of DNA profiling

  Crime scene forensics

  Paternity testing
• Genetic screening

  Testing for the presence or absence of a particular gene
• Mutations cause genes to

  Not produce protein that they were intended to produce (not carrying correct code)
• Gene mutation examples

  Cystic fibrosis, sickle cell anaemia
• Uses of genetic screening

  • Adult screening (check whether adult carries certain gene)
  • Foetal screening (detect genetic disorders in children)
• DNA

  • Number of strands= 2
  • Name of sugar= deoxyribose
  • Location= nucleus
  • 4 bases=

  Adenine

  Guanine

  Thymine

  Cytosine
• RNA

  • Number of strands= 1
  • Name of sugar= ribose
  • Location= ribosome
  • 4 bases=

  Adenine

  Guanine

  Uracil

  Cytosine
• mRNAfunction

  Carries a codon to ribosome and binds loosely to rRNA
• rRNA

  Structural component of the ribosome and binds loosely to mRNA
• tRNA

  Brings an anti-codon and an amino acid to ribosome and binds anti-codon to codon
• Site of protein synthesis

  Ribosome