Chapter 8 - Chromosome Variation Flashcards
aneuploidy
variation in chromosome number
failure of homologous chromosomes in _______ or sister chromatids in _____
meiosis I; meiosis II
animals are ______ of monosomies
intolerant
animals are _____ of trisomies
tolerant
trisomy 21
extra chromosome 21
caused by nondisjunction in ovum
how does maternal age cause trisomy 21?
long delay between meiosis I and meiosis II
patau
human trisomy
extra chromosome 13
50% death rate in first month
edwards
human trisomy
extra chromosome 18
survival: 2-3 months
warkany syndrome
human trisomy that is lethal in early embryo
extra chromosome 8
polyploidy
individual in a diploid species has more than two multiples of the haploid number of chromosomes (3n,4n,5n…)
autopolyploidy
whole set of chromosomes (3n,4n) are derived from parents that are related (same species)
allopolyploidy
hybridization between closely related species (i.e- plants)
colchicine
used to induce nondisjunction of chromosomes and polyploid function
American cotton example
shows allopolyploidy between an Old World strain and a wild North American strain
allotetraploid
tobacco example
shows allopolyploidy between two tobacco species
amphipolyploid
protoplast
plant cells with cell walls removed
endopolyploidy
cells in specific tissues may by polyploid in an otherwise diploid organism
deletion
structural change
loss of a section of a chromosome
cri-du-chat syndrome
deletion in humans
loss of one p arm on chromosome 5
duplication
structural change
duplication
structural change
sections of chromosomes occur in multiple copies
cause of duplication
unequal crossing over
gene amplification
genes that appear to be selectively duplicated
inversion
structural change where a segment of a chromosome is removed, rotated 180 degrees, and replaced
requires 2 breaks
paracentric
does not include centromere
does not change length
peircentric
includes centromere
can change length
crossing over in paracentric inversion loops produces _____
2 parental and two recombinant chromosomes
dicentric
contains 2 centromeres and can form a bridge that breaks randomly
acentric
lacks a centromere and drifts randomly
results of crossing over in a pericentric inversion loop
nonparental chromosomes with deletions and duplications
super genes
inversions can “lock in” favorable combinations of genes
super genes
inversions can “lock in” favorable combinations of genes
translocation
movement of chromosomal segments within or between chromosomes
reciprocal translocation
two nonhomologous chromosomes exchange segments
familial down syndrome
translocation in chromosomes 14 & 21
fragile chromosomes
areas within chromosomes that have sites that could potentially break
fragile sites in human genome
100+
fragile x syndrome (Martin-Bell)
fragile sites affect phenotype; extra copies of CGG of FMR-1 gene on X
mental retardation
more likely in men
number of repeats associated with expression of Fragile X
231+
FHIT Gene
frgile area on chromosome 3 that is inherited through maternal line
WWOX gene
on chromosome 16
encodes for tumor suppressor protein
