BSCI222 Genetics Unit Three

karyotypic diversity

how organisms vary in chromosome numbers (species living closer together vary more)

segmental duplication

partial duplication of chromosomal segment (e.g. Bar eye in fly)

tandem duplication

duplicated segment immediately adjacent to the original

dispersed/displaced duplication

duplicated segment distanced from original

aneuploidy

whole duplication of chromosome (individual) from nondisjunction in meiosis

nullisomy

type of aneuploidy missing 1 homologous pair

monosomy

type of aneuploidy missing 1 extra homologue (of pair)

trisomy

type of aneuploidy with 1 extra homologue (of pair)

tetrasomy

type of aneuploidy with 2 extra homologues (of pair)

Polyploidy

whole genome duplication (extra sets of chromosomes)

Autoploidy

duplication of a genome in a species

Allopolyploidy

duplication of different genomes in an interspecific hybrid

Diploidization

polyploid chromosomes evolve differences until they behave like diploids

once more

homologous genes

copies on matching pair

orthologous genes

copies on divergent pair

chromosome deletion

loss of a chromosome segment that leads to a loss of genes

pseudodominance

expression of normally recessive mutation

chromosome inversion

chromosome segments flip orientation (backwards) which disturb synapsis and meiosis crossing over

paracentric inversions

inversions not including centromere where parts of chromosomes are lost, making recombinants inviable

pericentric inversions

inversions including centromere where genes get lost, making the recombinant inviable

small inversions lead to…

low recombination

large inversions lead to…

high recombinations

translocations

movement of chromatin segment

nonreciprocal translocation

when genetic material moves from chromosome to chromosome without any reciprocal exchange

reciprocal translocation

a two way exchange between chromosomes

Robertsonian translocations

when two chromosomes fuse together