7.5 Chromosomal Abnormalities Flashcards
nondisjunction
chromosomes don’t separate properly during meiosis
autosome
chromosomes 1 - 22
sex chromosome
X- and Y-chromosomes
deletion
part of a chromosome doesn’t get copied during DNA replication
duplication
part of a chromosome gets copied too many times during DNA replication
inversion
part of a chromosomes gets copied backwards during DNA replication
translocation
non-homologous chromosomes swap pieces
nondisjunction in meiosis I
homologous chromosomes fail to separate
nondisjunction in meiosis I: gametes
two gametes have n + 1 chromosomes
two gametes have n - 1 chromosomes
nondisjunction in meiosis I: zygote
either has a trisomy or a monosomy
trisomy
2n + 1 chromosomes
monosomy
2n - 1 chromosomes
nondisjunction in meiosis II
sister chromatids fail to separate
nondisjunction in meiosis II: gametes
two gametes have n chromosomes
one gamete has n + 1 chromosomes
one gamete has n - 1 chromosomes
nondisjunction in meiosis II: zygote
can be normal, have a trisomy, or have a monosomy
nondisjunction: autosomes
almost always fatal
nondisjunction: sex chromosomes
humans are more tolerant of extra/missing sex chromosomes than autosomes
just needs at least one X-chromosome
deletion: gamete
missing gene(s)
deletion: zygote
missing gene(s) - only 1 copy instead of 2
duplication: gamete
extra gene(s)
duplication: zygote
extra gene(s) - 3 copies instead of 2
inversion: gamete
could be normal, could be fatal
inversion: zygote
might have trouble pairing homologous chromosomes during meiosis
translocation: gamete
depends on which chromatids end up in the gamete
could be normal, could have missing/extra gene(s)
translocation: zygote
depends on which chromatids end up in the zygote
could be normal, could have missing/extra gene(s)
