Topic 7.1 - Genetic Variation

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  • A difference in the characteristics of individulas of the same species may be caused by a difference in:
    • The genes that they have inherited- genetic causes
    • The conditions that they have developed in- environmental causes
      • Or a combination of the above
  • The information that results in plants and animals inheriting similar characteristis to their parents, is carried by genes
    • These are passed on in the sex cells (gametes) from which the offspring develop
  • The nucleus of a cell contains chromosomes 
    • Chromosomes carry genes that control the characteristics of the body
    • Chromosomes are normally found in pairs
  • In human body cells, one of the 23 pairs of chromosomes carry the genes that determine sex
    • In females the sex chromosomes are the same: **
    • In males the sex chromosomes are different: XY
  • Different genes control the development of different characteristics of an organism
    • Some characteristics are controlled by a single gene
      • Each gene may have different forms called alleles
  • If both chromosomes…

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