Molecular genetics

• why is DNA important

  1. DNA is the genetic material in living organisms (stores genetic information which controls characteristic of the organism. eg colour or eye, shape of nose, height etc)
  2. some diseases have a genetic link (eg some cancer, diabetes, heart disease)
  3. DNA in cells are inherited from parents (50% mother 50% father)
  4. some of these DNA will be passed to your children
• basic unit of DNA

  nucleotide

  1. a deoxyribose sugar
  2. a phosphate group
  3. a nitrogenous base

  nitrogenous base

  1. adenine
  2. thymine
  3. guanine
  4. cytosine
• structure of DNA

  1. nucleotides can be joined together to form long chains called polynucleotides
  2. a DNA molecules consists of 2 polynucleotide chains
  3. the bases of one chain are bonded to those of the opposite chain according to the rule of base pairing
  4. adenine bonded to thymine
  5. guanine bonded to cytosine
  6. complementary bases are held by hydrogen bonds
  7. the 2 polynucleotide strands are twisted into a spiral shape structure called a double helix
• gene

  a gene is a sequence of nucleotides, as part of a DNA molecule that codes for the formation of one polypeptide

  a gene is a unit of inheritance
• relationship among DNA, genes and chromosomes

  1. deoxyribonucleic acid is a molecule that carries genetic code, which is used to synthesize specific polypeptides
  2. each gene is a sequence of nucleotides, as part of a DNA molecule which codes for the formation of one polypeptide
  3. the polypeptide determines the characteristic of an organism
  4. a gene is a unit of inheritance
  5. chromosomes comprises of DNA wrapping around proteins
• functions of DNA

  1. deoxyribonucleic acid is a molecule that carries genetic codes, which are used to synthesize specific polypeptides
  2. the polypeptides control the functions of the cell and the characteristics of an organism
  3. DNA can be passed from one generation to another
• how is the polypeptide synthesized based on the genetic code

  1. part of the DNA unwinds
  2. message in the gene is copied into a molecules called messengerRNA (mRNA)
  3. mRNA leaves the nucleus through the nuclear pore and reaches the cytoplasm
  4. in cytoplasm, mRNA attaches to a ribosome
  5. ribosome moves along the mRNA synthesizing a polypeptide
  6. as the ribosome moves along the mRNA, the polypeptide produced gets longer as more amino acids are joined together by peptide bonds
  7. the polypeptide is released when the ribosome leaves the mRNA