B6 - Inheritance, variation and evolution

• Is DNA a polymer or a monomer?

  polymer
• What is DNA? 


  chemical that all genetic material in a cell is made from
• What is a gene?


  a small section of DNA found on a chromosome
• What do genes do?

  • code for a particular sequence of amino acids (making proteins)

  • tells cells what order to put amino acids
• What is a genome?


  entire set of genetic material in an organism
• What are the reasons for studying the human genome?


  • identify genes that are linked to different diseases

  • find which genes are linked to inherited diseases, could help find effective treatment

  • trace migration of certain populations of people
• What does each nucleotide consist of?

  • sugar

  • phosphate group

  • a base
• What forms the 'backbone'?

  • sugar

  • phosphate
• What base pairs with A?

  T
• What base pairs with T?

  A
• What base pairs with C?

  G
• What base pairs with G?

  C
• Where are proteins made in the cells?

  ribosomes
• How are codes moved from DNA to ribosomes?

  • mRNA is made by coping code from DNA

  -> it acts as a messager between DNA and ribosomes

  • amino acids bought to ribosomes in correct order by carrier molecules
• What are the uses of proteins?

  • enzymes - biological catalysts to speed up chemical reaction

  • hormones - carry messages around the body

  • structural protein - physically strong
• What is a mutation?


  a random change in DNA, can be inherited
• How can chance of mutation increase?

  exposure to certain substances or radiation
• What do mutations do?


  change the sequence of DNA bases, producing genetic variant and can lead to changes in protein code
• What are the 3 types of mutation?

  • insertion

  • deletion

  • substitution
• What is sexual reproduction?


  involves the fusion of male and female gametes, as there are two parents, offsprings contains mixture of parents genes
• What is asexual production?


  no fusion of gametes as there is one parent, so no mixing of chromosomes and no genetic variation - genetically identical to parent
• How are gametes produced?

  meiosis
• How does meiosis work?


  • genetic information duplicates - forming two armed chromosomes and arrange into pairs

  • first division - chromosomes line up in centre of cell

  • pairs are pulled apart - new cell has one copy of each chromosome

  • second division - chromosomes line up in centre of cell

  • arms of chromosomes are pulled apart

  • four gametes are produced with single set of chromosomes
• What are the advantages of sexual production?


  • variation increases chance of species surviving a change in environment

  • some characteristics make them better adapted meaning better chance of survival - more likely to breed successfully

  • selective breeding - used to produce animals with desirable characteristics meaning better and more food production
• What are the advantages of asexual reproduction?


  • only needs one parent

  • uses less energy

  • faster

  • many offspring can be produced in favourable conditions
• What chromosome causes male characteristics?


  Y
• What chromosomes do males have


  XY
• What chromosomes do females have?


  XX
• What did Mendel do?


  noted how characteristics in plants (peas) were passed on from one generation to the next
• What conclusions did Mendel reach?

  • characteristics in plants determined by 'hereditary units'

  • hereditary units passed onto offspring unchanged - one unit from each parent

  • hereditary units can be dominant or recessive
• What are the two types of variation?


  • genetic

  • environmental
• How does genetic variation work?

  • genes passed down from gametes

  • animals and some plants get some genes from mother and some from father

  • combining genes causes genetic variation

  • some characteristics are only controlled by genes: eye colour, blood group and inherited diseases
• How does environment variation work?

  conditions causes differences between same species
• How are characteristics variated by both genes and environment?

  e.g maximum height determined by genes but growing to that height is determined by environmental factors (amount of food)
• What is an allele?


  alternative version of a gene
• What is a genotype?


  what alleles you have
• What is a phenotype?


  what characteristics you have
• What is the theory of evolution?

  all of todays species evolved from simple life forms that developed 3 billion years ago
• What observation did Darwin see?


  survival of the fitest - organisms with the most suitable characteristics for the environment are more successful competitors making it more likey to survive
• What is speciation?


  when the pheotypes of organisms change so much due to natural selection a new species forms