Unit 8- Chromosome Variation Flashcards
Chromo Rearrangement
alter the structure of chromo
duplication
a seg of chromosome duplicated (can be inverted)
- tatem: duplicate next door
- displaced: duplicate elsewhere
*detected by looping
deletion
loss of a chromo seg
- large deletions easily detected; during pairing, normal chromo loops out
effects of deletions
- imbalances in gene product
- expression of a normally recessive gene (pseudodominance)
- haploinsufficiency: when a single copy of a dom allele is not enought to produce wild-type alleles
inversion
seg of chromo turned 180 degrees
- paracentric or pericentric
translocation
seg moves from chromo to a nonhomologous chromo or to another place on same chromo
inversions in meiosis
- homozygous: no problems arise
- heterozygous:
- homol seq align only if the 2 chromo form an inversion loop
nonreciprocal translocation
segment from ONE chromo goes to another
reciprocal translocation
segment from EACH chromo goes to the other
Robertsonian translocation
the entire long arms of two different chromosomes become fused (short arms fuse together too)
aneuploidy
inc or dec in # of indiv chromos
causes:
- deletion of centromere during mitosis/meiosis
- robertsonian translocation
- nondisjunction
Aneuploidy: nullisomy
loss of both members of a homologous pair of chromos; 2n-2
Aneuploidy: monosomy
loss of a single chromo; 2n-1
Aneuploidy: trisomy
gain of a single chromo; 2n+1
Aneuploidy: tetrasomy
gain of 2 homologous chromos; 2n+2
effects of aneuploidy
sex chromos:
- turners syndrome: XO
- Klinefelter Syndrome: XXY
autosomes
- trisomy 21: down syndrome (primary: 75% nondisjunction and familial: 25% robertsonian translocation)
uniparental disomy: both chromos inherited from same parent
Polyploidy
prescence of more than 2 SETS of chromos
significance:
- inc in cell size
-evolution
polyploidy: autoploidy
2+ sets from single species
polyploidy: allopolyploidy
2+ sets from 2 diff species
paracentric inversion
inversions that do not include centromere
- no recomb (nonviable offspring: chromo breaks off)
pericentric inversions
inversion that INCLUDE the centromere
- abnormal gametes
position effect
genes are expressed at wrong times or produce the wrong tissues due to inversion
uniparental disomy
both chromosomes are inherited from the same
parent (some cystic fibrosis and willi syndrome)
