3.4 Inheritance

• The law of segregation is that when gametes form, alleles are separated so that each gamete carries only one allele for each gene.
• The law of independent assortment is that the segregation of alleles for one gene occurs independently to that of any other gene.
• The principle of dominance is that recessive alleles will be masked by dominant alleles.
• The law of independent assortment does not hold true for genes located on the same chromosome.
• Codominance is when both phenotypes are equally expressed.
• Blood tYPE A is dominant.
• Blood Type B is dominant.
• Blood Type AB is codominant.
• Blood Type O is recessive.
• Cystic fibrosis is a recessive genetic disease. (double recessive allele pair)
• Huntington's disease is a dominant genetic disease. (only 1 allele needed to get disease)
• Sickle cell anemia is a codominant genetic disease. (double alleles=disease, 1 allele=lesser symptoms of disease)
• Autosomes are body chromosomes (pair 1-22)
• Allosomes are sex chromosomes (pair 23)
• Cystic fibrosis is a mutation in a gene on autosome pair 7.
• Individuals with cystic fibrosis produce mucus which is unusually thick and sticky clogging the airways and secretory ducts of the digestive system leading to to respiratory failure and pancreatic cysts.
• Huntington's disease is a mutation in a gene on autosome pair 4.
• Sickle cell anemia is a mutation in a gene on chromosome 11.
• Gregor Mendel discovered the principles of inheritance with experiments in which large numbers of pea plants were crossed.
• Gregor Mendel discovered that crossing two different purebred varieties together the results were not a blend and only one feature would be expressed. He also discovered that when the offspring were self-fertilized the resulting progeny expressed the two different traits in a ratio of 3:1.
• Gametes are haploid sex cells formed by the process of meiosis.
• The male gamete is sperm.
• The female gamete is ova.
• The y chromosome is smaller than the x chromosome.
• XY is male.
• XX is female.
• Colour blindness is a recessive sex linked disease.
• Haemophilia is a recessive sex linked disease where the blood is incapable of clotting.
• Hiroshima and Chernobyl both released radioactive isotopes into the environment exposing humans and other organisms to dangerous levels of radiation.