notes

• locus

  • position of genes on chromosomes
  • each gene occupies specific locus so that gene for a particular characteristic is always found at same position on a chromsome
  • each gene can exist in 2 or more different forms- alleles
• autosomal linkage

  • autosome- any non-sex chromosome
  • 2 or more genes on same autosome do not assort independantly during meosis
  • they are linked and stay together in original parental combo
  • closer loci of genes on chromosome- more closely linked- less likely to be seperated during crossing over in meosis
• sex linkage

  • females= XX males=XY
  • Y is shorter
  • some genes only present on 1 sex chromosome, X or Y
  • mostly sex linked genes found on the longer X chromosome
  • genes on X chromosomes, sometimes males only have 1 copy whereas females have 2 (XX)
  • as males only have 1 X, much more likely to show sex linked recessive conditions