CB3 Genetics

• meiosis is The production of :

  • four daughter cells
  • each cell only has one copy of every chromosome and so is haploid

  genetically different gametes are formed
• • Chromosomes are made of DNA.
• structure of DNA =

  • DNA is a double helix shape.
  • Made from 4 complementary bases (G,C,A,T)
  • Base pairs joined by HYDROGEN bonds. A to T = 2 bonds, G to C = 3 bonds
  • Sides are made of sugar and phosphate
  • Sections of DNA are called GENES.

  Each gene codes for the production of a PROTEIN
• phosphate to sugar to base
•  

  Homogenise cells;

  Crush fruit with a pestle and mortar to grind cells and release DNA

  Detergent;

  Breaks open the cell membranes to release the DNA from the cell.

  Protease enzyme;

  Breaks up proteins so it will break up DNA into smaller sections.

  Ethanol;

  Precipitates the DNA and separates it from the other parts of the cell as it makes the DNA form a precipitate.
• • Chromosomes are found in the nucleus of a cell.
  • Chromosomes are made of genes
  • Genes control our characteristics by controlling the production of PROTEINS.
• We have two of every chromosome.
• Alternative forms of the same gene are called ALLELES.
• Alleles can be dominant or recessive.
• Only one dominant allele is needed for it to show in the PHENOTYPE. Two recessive alleles are needed for it to show in the phenotype.
• genotype = the alleles an organism has e.g. Aa 
• phenotype = What characteristic an organism has e.g. blue eyes
• dominant = The stronger allele – only one is needed for the phenotype to be shown e.g. A
• recessive = The weaker allele – two are needed for the phenotype to be shown e.g. a
• homozygous = Having two of the SAME alleles e.g. AA or aa
• heterozygous = Having two DIFFERENT alleles e.g. Aa
• zygote = A fertilised egg – once the egg and sperm have fused together
• If we know the alleles that two parents have then we can predict the genotypes of their offspring using a Punnett square.
• MONOHYBRID INHERITANCE. This means that it is showing just ONE GENE.
• Family pedigree charts allow couples to be able to know the chances of a genetic disorder being passed on to any children that they may have.
• Possible benefits the HGP are :

  1. New treatments or cures for some genetic disorders may be found
  2. Help to produce personalised medicines that might be best to treat a person’s illness as the alleles we have can affect how well medicines work.
  3. Locate the genes associated with certain diseases.
• A mutation is a change in the sequence of bases in the DNA which can cause a change in the order of amino acids and the protein produced. 

  They mostly happen when new DNA is being made during interphase.
• Mutations are caused by:

  1. Damage to DNA e.g. by radiation or chemicals.
  2. Naturally happening.
• Mutations are the mean reason why genetic variations occur within a species.
• The two CAUSES of variation are GENETIC and ENVIRONMENTAL
• DISCONTINUOUS VARIATION;

  there are definite groups that you can belong to.
• Genetic characteristics mostly show discontinuous variation.
• CONTINUOUS VARIATION.

  there not easily defined groups that you can belong to.
• Environmental characteristics mostly show continuous variation.