b1

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  • Created by: bwillows1
  • Created on: 11-05-14 10:48
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  • B1
    • genes chromosomes and DNA
      • most cells in body have nucleus
        • containing genetic material
          • arranged in chromosomes
            • 23 pairs
            • each chromosome is 1 long molecule of DNA
              • coiled up
            • gene is a short length of a chromosome
      • genes can exist in different versions
        • each version = different characteristic
          • different versions of the same gene = ALLELES
        • control development of characteristics
      • each gene is a code for making a certain protein
        • proteins are building blocks of cells
          • having different proteins = different characteristics
        • STRUCTURAL PROTEINS
          • part of things like skin/hair/blood/ cytoplasm in cells
            • e.g collagen = structural protein found in tendon/bone & cartilage
        • FUNCTIONAL PROTEINS
          • E.g - enzymes are proteins that help with digestion by breaking down food molecules
            • amylase breaks down starch to maltose
      • an organisms genotype is all the genes it has
        • characteristics and organism displays is its phenotype
          • some characteristics are controlled by only genes
            • eye colour
            • dimples
          • some characteristics are only controlled by environment
            • scars
          • some caused by both
            • weight
    • genes and variation
      • sex cells have 23 single chromosomes
      • alleles are different versions of the same gene
      • children resemble both parents
        • not identical to any
      • 2 chromosomes in a pair are never identical because of different alleles
        • when people produce sperm and egg cells their pairs of chromosomes separate and go into different cells.
          • sex cells produced by individuals are genetically different
            • variations
    • inheritance and genetic diagrams
      • combination of alleles determines phenotype
        • 2 of same gene (1 from each parent)
        • HOMOZYGOUS
          • 2 alleles of the SAME gene
        • HETEROZYGOUS
          • 2 DIFFERENT alleles for the gene
      • alleles can be dominant or recessive
        • characteristics caused by dominant alleles will be shown
          • DOMINANT
            • capital
          • recessive
            • lower case
    • genetic diagrams and sex chromosomes
      • punnet squares
      • men
        • XY
          • Y chromosome gives male characteristics
      • women
        • XX
      • the gene that makes embryo into a male causes a specific protein to be formed
        • causes development of testes
          • testes produces male sex hormone
        • in females the protein is not produced
          • formation of ovaries
    • genetic disorders
      • some inherited
        • one or both parents carry faulty allele and pass it on to their children
      • caused by faulty alleles
        • Cystic fibrosis and huntingtons are both caused by faulty alleles of a single gene
          • cystic fibrosis
            • caused by recessive alleles
              • genetic disorder of the cell membranes caused by faulty recessive alleles.
            • symptoms
              • thick sticky mucus in air passages, gut and pancreas
              • breathing difficulty
              • chest infections (painful coughing)
              • difficulty in digesting food
            • because it is recessive, people with only 1 copy of the allele wont show symptoms
              • CARRIERS
                • both parents must be characters or sufferers for child to get disorder
          • Huntingtons
            • caused by a dominant allele
              • means 50% chance of each child inheriting disorder if 1 parent is carrier
                • carrier parent with of course be a sufferer because allele is dominant
                  • late onset, after age of 40

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