Variation and inheritance

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  • Created by: GraceLong
  • Created on: 23-05-16 16:36
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  • Variation and inheritance
    • Inherited characteristics
      • Inherited characteristics can be dominant or recessive
      • Alleles are different versions of the same gene
      • There are debates about how much 'nature or nurture' effects intelligence, health and sporting ability
      • Dominant and recessive characteristics depend on dominant and recessive alleles
      • Dominant alleles are expressed when present but recessive alleles are expressed in the absence of the dominant allele
    • Monohybrid corss
      • Involves one pair of characteristics controlled by single gene - one dominant and one recessive allele
      • Homozygous has identical alleles and hetrozygous has different alleles
      • A persons genotype is their genetic make up whereas a persons phenotype is the allele expressed
    • Chromosomes
      • Sex chromosomes in mammals determine sex. Females have XX and male have XY
      • There is a random chance of which sperm fertilises an egg... therefore an equal chance of male or female
      • A sperm will carry either an X or a Y. The egg always contains the X chromosome
      • Most cells have the same number of chromosomes depending on the species. Humans have 23 pairs
    • Inherited disorders
      • Usually caused by faulty alleles that are recessive
      • Ethical issues raised about having screening for genetic disorders and knowing the risks of passing on a genetic disorder
      • Caused by faulty genes
      • It is possible to predict the probability of inheriting orders using genetic diagrams
    • Genetic variation
      • Caused by: fertilisation resulting in zygote from father and mother
      • Caused by: mutations which randomly change genes or chromosomes
      • Caused by: rearrangement during formation of gametes


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