DNA

• DNA contains all genetic information required to make you! The shape of it is called double helix, and it is made up of two strands.
• The strands are connected by molecules called bases. There are 4 bases (A,T,C,G). The A and T are always together, and the C and G are always together.
• Roslyn Francis produced Photo 51, an X-ray that helped us to see the structure of DNA, Watson and Crick were the two scientists involved in the discovery of the shape of DNA.
• Extraction of DNA:

  Washing up liquid helps break the cell membrane and nuclei apart, releasing the DNA.

  Salt solution helps the DNA strands to stick to each other in clumps large enough to see.

  Alcohol helps DNA clumps to form.
• Examples of applications of DNA profiling include identifying crime and catastrophe victims, establishing paternity and other family relationships and human origins and culture.
• A gene is a short length of DNA that carries the instructions for a characteristic (e.g. blue eyes).
• variation is the differences in characteristics between organisms of a species due to differences in the genes.
• Variation can be due to:

  the genes that have been inherited (genetic variation);

  the conditions in which they have developed (environmental causes);

  a combination of genes and the environment.
• Some examples of characteristics that can be influenced by the environment are;

  • scars
  • weight
  • hair length
• The two types of variation are discrete and continuous variation.
• Discrete variations in organisms are characteristics that fit into one group or another such as eye colour or (natural) hair colour.
• Continuous variations in organisms don't fit into the categories but can be measured and show a range of differences. An example of this is height.
• Genes that code for a characteristic come in different forms called alleles. You will get one form of gene from your mother and one from your father.
• Alleles are different forms of a gene.
• Dominant is the "stronger" version of a gene.
• Recessive is a version of a gene that is "hidden" by a dominant version.
• Homozygous are if the two alleles are the same.
• Heterozygous is when the two alleles are different.
• A genotype is the combination of alleles for a characteristic.
• A phenotype is the way that the the genes are expressed (what the organism looks likes).
• Genetic engineering is when a gene is taken from one organism and put into the DNA of another organism.
• Examples of organisms that go through genetic engineering are:

  Spider goat

  Golden rice

  Glow in the dark mice

  Venomous cabbage