ocr 21st century science B1

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  • B1-You and your genes
    • Variation
      • Order of size (large to small): Cell, nucleus, chromosomes, DNA, gene, base
      • Nucleus, DNA and proteins provide instructions. Your diet is the ingredients.
      • Functional Proteins: enzymes - anylase, protease
        • Nucleus, DNA and proteins provide instructions. Your diet is the ingredients.
      • Structural proteins: e.g. hair, skin, blood, cytoplasm
        • Functional Proteins: enzymes - anylase, protease
      • Gender and the rule of genes
        • Normal cells contain 23 pairs of chromosomes. Sex cells contain 23 single chromosomes. Pair 23 determines the gender. Women = XX, Men = XY.
        • Genotype = genetic make up, e.g. Ff, FF, ff. Phenotype = physical expression of a gene, e.g. brown hair
        • Homozygous = same two identical alleles, e.g. FF, ff. Heterozygous = different alleles for an inherited characteristic, e.g. Ff
        • allele = different versions of the same gene on a chromosome
      • Inherited disorders
        • Dominant disorders - need only one copy
          • Huntington's disorder - no carriers because of dominance
            • affects nervous system - causes involuntary movement, dementia
        • Recessive genes - weak, need 2 copies
          • Cystic Fibrosis - can have carriers
            • affects cells membrane - causes thick, sticky mucas in lungs, gut, pancreas
      • Embryo Selection
        • PGD - preimplantation genetic diagnosis. Take fertility drug; doctor collects egg; sperm fertilise in petri dish (in vitro fertilisation); at eight cells, one cell is removed; tested for disorders; healthy embryos returned to womb
        • not 100% accurate (false negative and false positive)
      • Cloning
        • Stem cells - unspecialised, found in marrow and embryos; can grow into any type of cell
        • Natural clone = identical twins as the fertilised cell splits
          • not always identical because of the evironment
        • unicellular = one celled organism
        • asexual reproduction
    • Ethics
      • Embryo Selection
        • PGD - preimplantation genetic diagnosis. Take fertility drug; doctor collects egg; sperm fertilise in petri dish (in vitro fertilisation); at eight cells, one cell is removed; tested for disorders; healthy embryos returned to womb
        • not 100% accurate (false negative and false positive)
      • HFEA - a regulating body.
      • Scientists - framework, for the greater good population
      • Politicians -  rights
      • Indervidual's consent
      • Choices: adopt, test (chance of miscarriage), abortion, no tests (could have disorder)
    • Egg cell = X, Sperm cell = X or Y. 50% chance of each gender, Sperm decide.
      • Normal cells contain 23 pairs of chromosomes. Sex cells contain 23 single chromosomes. Pair 23 determines the gender. Women = XX, Men = XY.

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