Inheritance

• Chromosome


  A long, coiled molecule of DNA that carries genetic information in the form of genes
• Alleles


  Different versions of the same gene
• Homozygous


  Having two identical alleles of a gene e.g. FF or ff
• Heterozygous 


  Having two different alleles of a gene e.g. Ff
• Monohybrid inheritance 


  The inheritance of a single gene
• Wha this the problem with single gene crosses?

  Most characteristics are controlled by multiple alleles rather than just one
• Sex chromosomes

  A pair of chromosomes that determine sex :

  • Males have an X and a Y chromosome

  • Females have two X chromosomes
• Why does the inheritance of a Y chromosome mean thar an embryo develops into a male?

  Testes development in an embryo is stimulated by a gene present on the Y chromosome
• Other than using a punnett square, how can monophonic inheritance be represented?

  Using a family pedigree
• Why are the majority of genes found on the X chromosome rather than on the Y chromosome?

  The X chromosome is bigger than the Y chromosome so more genes are carried on it