Topic 3- genetics

• Asexual reproduction - generates genetically identical offspring without the need for gametes. No need to find a mate, so quick, no variation in population though.
• Sexual reproduction - The process of producing offspring through fusion of gametes from two parents.
• Meiotic cell division - the production of four daughter cells (genetically different haploid gametes), each with half the number of chromosomes.
• The DNA molecule is a double helix made up of two strands. Linked by a series of complimentary base pairs, joined together by weak hydrogen bonds.
• Adenine and Thymine.
• Cytosine and Guanine.
• Gene - section of a molecule of DNA that codes for a specific protein.
• Genome - the entire DNA of an organism.
• Extracting DNA from fruits:

  • Mash the flesh of fruits.
  • Mix with detergent, salt and water - detergent dissolves nucleus and cell membranes, salt breaks up protein attached to DNA.
  • Mash again - more mashing=more DNA.
  • Heat to 60 degrees for 15 minutes - to break down proteins.
  • Filter to remove bits.
  • Pour ice-cold alcohol down the side of the container - to form a transparent layer on top.
  • DNA is insoluble in the cold alcohol and white strands in a jelly-like substance will start to precipitate out.
  • Extract the long coagulated strands of DNA.
• Mutations in the non-coding DNA can affect phenotype, by influencing binding of RNA polymerase and altering quantity of protein produced.
• Transcription:

  • mRNA is produced in the nucleus
  • It carries complimentary genetic information from the DNA to the ribosome.
  • The mRNA carries specific triplets of bases (codons) that code for specific amino acids.
  • RNA polymerase binds to non-coding DNA in front of gene to produce complimentary mRNA from coding strand.
• Translation:

  • tRNA carries these amino acids to the ribosome - where the amino acids link to form polypeptides in an order decided by mRNA.
  • The order of the bases in a section of DNA, therefore decides the order of amino acids in a protein.
  • Each protein has its own specific number and sequence of amino acids - different shaped molecules, with different functions, including enzymes.
  • Gene mutations change the DNA base sequence.
• Mendel - plants must have two inheritable factors for each characteristic.
• Dominant allele - characteristics of this allele are expressed even when only one is present.
• Recessive allele - both recessive alleles have to be present for the characteristics to be expressed.
• Gametes - are an organisms reproductive cells.
• Zygote - when a sperm fertilises an egg, the resulting zygote contains all the genetic information for the new organism.
• Genotype - the composition of alleles (BB, Bb, bb).
• Phenotype - the observable characteristics (blue/brown eyes).
• Continuous data is data that can take on any value between two limits.
• Discontinuous data - specific total/number.
• The Human Genome Project has successfully identified the 3.2 billion base pairs that make up some 20,500 genes in the DNA of the 23 chromosomes in humans.