BIOL 201 Lecture Notes - Sister Chromatids, Nuclear Membrane, Meiosis
Document Summary
Mendel"s 2nd law of independent assortment (anaphase i and ii: alleles for one gene segregate independently with the alleles of another gene (ggbb, two genes for each characteristic segregate during gamete production (gb)(gb)(gb)(gb) Independent assortment means either g / g can go with either of b / b: meiosis separates alleles / homologous chromosomes, dihybrid inheritance (two genes - 9:3:3:1 ratio) occurs at different loci. Human abo group is controlled by the immunoglobulin gene i: the immunoglobulin gene has 3 alleles ia, ib, i0, these alleles code for antigen a, b, neither a/b, respectively. Only 2 alleles can be present in a diploid cell iaib is codominant, i0 recessive. Heterozygous allele is neither dominant nor recessive both alleles are expressed. Sex linkage e. g. haemophilia clotting time of blood is longer than usual. Inheritance of sex in humans: females are homogametic sex (x: or xx, males are heterogametic sex (xy) / y chromosome is shorter.