inheritance

• Meiosis is a form of cell division that gives rise to genetic variation; its main role is the production of haploid gametes as cells produced by meiosis have half the number of chromosomes
• Reduction division in meiosis takes place where the chromosome number halves from diploid to haploid
• Meiosis produces genetically different cells through:

  • Crossing over of chromatids where pairs of chromosomes exchange genetic material
  • Independent assortment of chromosomes leading to various combinations of chromosome arrangement
• During fertilisation, the random fusion of gametes increases genetic variation in offspring
• Monohybrid crosses are used to predict the ratios of inherited characteristics in a population, determining the outcome of one gene with a 3:1 ratio where the dominant trait is more common
• Dihybrid crosses are used to determine the outcome of two genes, each with two alleles, resulting in 16 outcomes
• Albinism affects melanin production, leading to white hair, light eyes, and pale skin due to a mutation in the TYR gene affecting tyrosinase production
• Sickle cell anaemia results from a mutation in the HBB gene altering hemoglobin production, leading to crescent-shaped red blood cells and insufficient oxygen transport
• Hemophilia, a sex-linked recessive disorder, results from a mutation in the FB gene causing a factor VIII deficiency, affecting blood clotting mainly in males
• Huntington's disease, a neurodegenerative disease, is caused by a mutation in the HTT gene affecting the production of huntingtin protein
• The chi-squared test is a statistical test used to establish if the difference between observed and expected results is significant or due to chance, comparing the obtained value to the critical value
• Mutations are changes in the sequence of nucleotides in DNA molecules, including insertion/deletion mutations, point mutations/substitutions, and nonsense mutations
• Mutations can result in a frameshift, point mutation/substitution, nonsense mutation, missense mutation, or silent mutation
• Frameshift mutations occur after an insertion/deletion point, causing a shift in the sequence of nucleotides
• Point mutation/substitution replaces one base pair with another, potentially with no effect
• Nonsense mutation stops translation early, leading to a truncated polypeptide due to a premature stop codon
• Missense mutation changes a codon, producing a different amino acid and altering the protein's tertiary structure
• Nonsense mutation stops translation early, leading to a truncated polypeptide due to a premature stop codon