topic 6

• DNA makes genetic material
• DNA determines the inherited characteristics
• DNA is found in the nuclei of plant and animal cells
• DNA is a polymer - 2 strands coiled together in a double helix shape
• each gene codes for a particular sequence of amino acids which are put together to make specific proteins
• genes tell a cell what order to put the amino acids in
• DNA determines what protein the cell produces
• the genome is an entire set of genetic material in an organism
• you can use a genome to track migration
• DNA is made up of repeating units called nucleotides - each nucleotide cosists of one sugar, one phosphate and a base
• A goes to T
• C goes to G
• proteins are made in ribosomes - ribosomes need DNA to make proteins - DNA cant leave the nuclei so molecule mRNA copies the code and acts as a messenger between ribosomes and DNA
• correct amino acids are carried to the ribosomes in the correct order by carrier molecules
• mutation is when an organisms DNA changes
• mutation can be inherited or if the chromosomes have being incorrectly replicated
• mutation 


  changes the sequence of DNA bases - changes the amino acids it codes for so can change the protein
• insertion

  1. when a base is inserted into a DNA sequence that shouldn't be there
  2. every 3 bases code for a different amino acid
  3. if you change a base it changes the way the group of 3 bases is read and changes the amino acid it codes for
• deletion

  1. a base is deleted which changes the way the sequence is read
• substitution


  random bases are changed which changes the amino acid thats coded for
• sexual reproduction

  1. involves fusion of male and female gametes
  2. offspring contains mix of genetic material
  3. meiosis
• asexual reproduction

  1. no genetic variation
  2. mitosis
  3. only 1 parent
• meiosis

  1. genetic information is replicated
  2. chromosome arrange into pairs
  3. chromosomes line up at centre
  4. chromosomes are pulled apart to form new cells with 1 type of each chromosome which are a mix of the mother and fathers
  5. chromosome line up at centre again and arms are pulled apart forming 4 gametes each with new single set of chromosomes
• parasites reproduce sexually when carried by mosquito and asexual when on a human
• genotype is a combination of alleles
• all genes exist in different versions of alleles
• cystic fibrosis has a recessive allele
• cystic fibrosis is where lots of thick mucus builds up in air passages and pancreas
• prodactyly is born with extra fingers or toes and has a dominant allele
• During IVF embryos are fertilised and implanted into mothers womb
• before an Embryos is implanted into the mother you can remove some cells and analyse the genes to detect genetic disorders
• For screening embryos

  1. Stop suffering
  2. save NHS money
  3. laws to prevent people wanting desired characteristics
• Against screening embryos

  1. Disabilities seen as undesired
  2. expensive
  3. want to create a child
• Mendel noted how characteristics of peas were passed on in the mid 19th century
• 1. Mendel started with a tall plant and a dwarf plant resulting in all tall plants
  2. a tall plant and a tall plant had 1 dwarf plant
• Mendels conclusion that characteristics were developed by hereditary units
• Variation is when an organism of the same species has differences
• Genetic variation is determined by things passed on from parents
• Environmental variation is determined from changes in the environment
• Mutations introduce variation