Genetics

• Meiosis


  A type of cell division that only happens in reproductive organs and produces gametes. It is different to mitosis because it doesn't produce identical cells
• Meiosis process


  A cell splits apart twice, resulting in four haploid daughter cells. These are gametes which only have a half set of chromosomes. They are all genetically different because the father and mother chromosomes arent all the same in each daughter cell.
• Gametes


  Reproductive cells like sperm and egg cells
• Haploid


  Only containing half the number of chromosomes of a normal cell
• Diploid


  Containing the full amount of chromosomes a cell has
• Zygote


  A fertilised egg caused by a male and female gamete fusing together
• DNA and its structure

  DNA is a polymer that is:

  • two strands coiled to form a double helix
  • strands linked by a series of complementary base pairs joined together by weak hydrogen bond
  • nucleotides that consist of a sugar and phosphate group with one of the four different bases attached to the sugar (A,T,C,G)
• Chromosomes


  Long, coiled up molecules of DNA. Found in the nucleus.
• Gene


  A section of DNA on a chromosome that codes for a particular protein. A sequence of bases in the gene determine what protein is produced.
• Genome


  All of an organisms DNA
• DNA extraction from fruit

  1. Grind up half of a kiwi in a pestle and mortar. Add washing up liquid and salt and mix well
  2. Filter the mixture and take the solution and heat in a water bath for 15 minutes at 60 degrees
  3. Take out and cool in an ice bath
  4. Add some ice cold ethanol at a 45 degree angle to the mixture
  5. The DNA will begin to appear as stringy white precipitate, fish this out with a wooden stick or glass rod
• Alleles


  You have two versions of every gene in you body- one on each chromosome in a pair. If an organism has two alleles that are the same, it is a homozygous trait and if they are different it is heterozygous. Alleles can be described as dominant or recessive, and if dominant is present, then it is the dominant allele that will be expressed. We get these alleles from our parents combination so not one person has the same set of alleles.
• Genotype


  An organisms combination of alleles
• Phenotype


  The characteristics an organism has because of their alleles
• Monohybrid inheritance

  The inheritance of a single characteristic is called monohybrid inheritance . You can use a monohybrid cross, a genetic diagram, a family pedigree, or a punnett square to see how the recessive and dominant traits for a characteristic are inherited
• Punnett square

  • Used to determine dominant and recessive allele inheritance

  
• Genetic diagrams

  • Show how sex is determined in humans through XX and XY chromosomes

  
• Family pedigrees

  • Used to interpret who is at risk or has a genetic disorder from looking at the alleles of the disorder in terms of carriers being recessive and inheritors being dominant

  
• Sex is determined at fertilisation. This is because egg cells contain one X chromosome and a sperm cells either contains an X or a Y. This means it depends on which sperm- X or Y- fertilises the egg first in order to see if it is XX- a girl- or XY- a boy.
• Most phenotypic traits come from multiple genes rather than one single gene inheritance. Children generally look a little like their mother and their father, but are not identical to either. They inherit their features from each parent's DNA.
• What influences variation?

  • Genetic variation- organisms having different alleles leading to different phenotypes or through mutation of genes
  • Environmental variation- the conditions in which an organism lives can influence the phenotype as acquired characteristics
• The Human Genome Project

  Outcomes: Scientists collaborated to find every single gene in the human body (which so far is 20,500)
• The Human Genome Project potential medical applications

  • Prediction and prevention of diseases- many common diseases are caused by interaction of different genes. If doctors knew which genes cause these disease interactions they can give advice.
  • Testing and treatment for inherited disorders- Scientists are able to identify the genes and alleles that cause inherited disorder much quicker and develop better cures
  • New and better medicines- Scientists can use this knowledge to tailor new drugs specifically to people with a particular genetic variation
• Genetic mutations


  Mutations are changes to the base sequences of DNA. They result in an allele or different type of gene. They are not likely to have a big effect on an organism but if they do have a small effect it can effect their phenotype and cause more genetic variation within.
• Mutations causing big effects

  They may result in a production of a protein that is so different it can no longer carry out its function. This results in genetic disorders such as Cystic Fibrosis.