B1

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  • You and your genes
    • What genes are and how they work
      • Genes carry the instructions that control how you develop and function. They do this by telling the cells to make the proteins needed for your body to work.
      • Functional proteins enable the body to function.
      • Structural proteins give the body structure, rigidity and strength.
    • How genes and chromosomes are organised
      • At fertilisation, an egg and sperm join together to produce a zygote.
    • Pairs of alleles
      • If the two alleles of a gene are identical, the person is said to be homozygous
      • If the two alleles of a gene are identical, the person is said to be heterozygous.
    • Genetic testing
      • Genetic screening is used to check for a particular disorder, even when there is no history of it in the family.
      • Genetic testing of individuals is carried out when a genetic disease, such as cystic fibrosis, runs in the family.
      • Embryo screening is used to investigate families with a known history of a disorder, such as cystic fibrosis.
    • Cloning
      • The disadvantage of producing clones is that there could be no genetic variation. This means that if conditions change or there is disease, the population could be wiped out.
      • The advantage of clones are that: successful characteristics are seen in offspring. Asexual reproduction is useful where plants and animals live in isolation.
    • Stem cells
      • Embryonic stem cells are unspecialised.
      • Adult stem cells are specialised.

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