CB3- Genetics

• Meiosis 


  Produces 4 haploid cells which are genetically varied

  ---> production of gametes
• Genome 


  The DNA of an organism
• Genes 


  Sections that contain a code for making protein
• Structure of DNA 


  Two strands coiled up together to from a double helix
• Hydrogen Bonds

  Parts of DNA bases have slight electrical charges

  A slight negative base attracts a slight positive base forming a weak force of attraction called hydrogen bonds
• Nucleotide 


  A= Sugar

  B= Phosphate

  C= Base

  
• DNA Extraction: Core Practical

  1. Mix a sample of fruit with a solution of salt , detergent and protease
  2. Mash the above step in a sealed bag
  3. Place in a water bath at 60 for 15 mins
  4. Filter the sample and collect the filtrate
  5. Place 10cm^3 of filtrate into a test tube
  6. Carefully add ice cold ethanol to test tube and leave for 5 mins
• Application

  One DNA has been extracted it can be used in a variety of ways:

  Paternity testing

  Food testing
• Reasons for equipment use:

  Mashing up- starts to break down cell wall

  Detergent- breaks the membrane

  Protease- breaks down the protein

  Salt- separates cells , clumps the DNA together and breaks down cell wall

  Ice cold ethanol- makes DNA insoluble and form a precipitate
• Chromosome 


  Structure found in the nucleus made up of a long strand of DNA carrying genetic information in the form of genes
• Gene 


  Short section of DNA coding for protein , contributes to characteristics
• Allele 


  The different forms of the same gene
• Dominant Allele 


  Only one is needed for it to be expressed
• Recessive Allele 


  Two copies are needed for it to be expressed
• Homozygous 


  Both inherited alleles are the same
• Heterozygous 


  One of the inherited alleles is dominant other is recessive
• Genotype 


  The combination of alleles that control each characteristic
• Phenotype 


  Physical Characteristics of an organism
• Gamete


  Sex cells
• Zygote 


  A fertilized egg cell
• There are differences in inherited characteristics as genes for the same characteristic can contain slightly different instructions and different alleles code for different forms of the same protein
• Determining Sex

  Males = XY

  Females = XX

  Punnett squares can be used to show sex inheritance
• Most phenotypic features are the result of multiple genes acting together and not single genes
• Causes of Variation- Genetic Variation

  Differences made can be due to mutations and sexual reproduction . Mutations happen when there is a mistake in copying the DNA during cell division producing new phenotypic characteristics whereas sexual reproduction is the combination of both the mum and dad
• Causes of Variation- Environmental Variation

  Characteristics can be caused by the environment but these changes are not heritable ( no change in the DNA )
• Human Genome Project

  THE HUMAN GENOME HAS BEEN STUDIED AND THIS HAS:

  Improved our understanding of the genes linked to different types of diseases

  Helped in the treatment of inherited disorders

  Helped in tracing human migration patterns from the past

  ---> Better understanding of which genes cause inherited disorders and which are linked
• There is usually extensive genetic variation within a population of species which arises through random mutations
• Genetic mutations varying effects on Phenotype

  Majority of mutations have no effect on the phenotype as they occur in the DNA which does not code for protein

  Some mutations can have a small effect on the phenotype

  Rarely , a mutation can significantly affect the phenotype - one base can change one amino acid in a protein . If protein was an enzyme , it has potential to change it's active site so substrate can't bind to it