Genetics

• A zygote is formed when two gametes fuse during fertilisation. The zygote then forms a ball of cells called mitosis.
• Meiosis is needed to produce gametes. Meiosis produces 4 daughter cells, each with half the number of chromosomes, and that this results in the formation of genetically different haploid gametes.
• The nuclei of your cells contain very long molecules of DNA. Each molecule is tightly coiled and packaged up with proteins to form chromosomes
• Structure of DNA:

  • polymer made up of two strands coiled to form a double helix
  • strands linked be a series of complimentary base pairs joined together by weak hydrogen bonds
  • nucleotides that consist of a sugar, phosphate group and base.
• The sugar and phosphate form the backbone. The bases form complimentary pairs:

  • A pairs T
  • C pairs G
• The order of bases in a gene codes for a protein. We all have slightly differences in our genes caused by slightly different orders of bases in our DNA.
• There are two copies of every chromosomes in a body cell nucleus. So a body cell contains two copies of every gene. Each copy of a gene may be different allele.
• The combination of alleles in each person gives each of us slightly different characteristics (genetic variation)
• DNA extraction:

  1. mash the fruit
  2. add a solution of salt, wahsing up liquid and water ( this breaks own membranes and allows DNA to be released from the cells/nuclei)
  3. place this mixture in a water bath at 60 degrees for 5 minutes
  4. filter th emixture and por the filtrate into a boiling tube
  5. add tow drops of protease enzyme solution (to break down the proteins covering DNA )
  6. tilt the boiling tube slightly and pour in the ice cold ethanol slowly (equal amount to the filtrate)
• DNA is insoluble in ethanol so it forms a white precipitate