10.2 Flashcards
what are the types of chromosome number variations?
aneuploidy (change in number of INDIVIDUAL chromosomes)
polyploidy (change in number of SETS of chromosomes)
what is the difference between ___somy and ___ploidy?
somy - number of particular chromosomes
ploidy - total number of chromosomes
what the most common types of aneuploidy in diploids (2n)?
nullisomy (lose both)
monosomy (lose one)
trisomy (gain one)
tetrasomy (gain both)
what is double-monosomic?
lose two non-homologous chromosomes
what is double trisomic?
gain two non-homologous chromosomes
how does aneuploidy occur?
nondisjunction and deletions of centromeres
what is nondisjunction?
failure of homo chromosomes or sister chromatids to seperate
what is the outcome of non-disjunction?
trisomy - may be viable
monosomy - only viable for sex chromosomes
what is Turner syndrome?
monsomy X
what is klinefelter syndrome?
extra copies of X
what is edwards syndrome?
trisomy 18
what is patau syndrome?
trisomy 13
what is primary down syndrome?
trisomy 21
most common type
usually random non-disjunction in mom
what is familial down syndrome?
extra chromosome 21 is attached to another chromosome (14 or 15 usually)
3-4% of cases
how does familial down syndrome happen?
parent carries chromosome that underwent robertsonian translocation (exchange of long arms of non-homologous acrocentric chromosomes)
what are the most frequent trisomies?
higher number (or sex) chromosomes - more viable because less genetic information
is aneuploidy tolerated in plants?
yes - much better than in humans
where is polylpoidy found?
sometimes in fish, reptiles, amphibians, invertebrates
not found in mammals and birds
very important and common in plants
what are the two types of polyploidy?
autopolyploidy - multiples of same genome
allopolyploidy - multiples of closely related genomes (different species)
where does polyploidy come from?
nondisjunction in mitosis or meiosis
what produces autotetraploidy?
nondisjuction of all chromosomes in mitosis in early embryo
what causes diploid gametes?
nondisjunction of all chromosomes during meiosis
what causes autotriploid?
diploid gamete + normal gamete
what causes autotetraploid?
diploid gamete + diploid gamete
what are the effects of autopolyploidy?
usually sterility (odd numbered ploidy)
most are genetically unbalanced
how do you make sterile hybrid plants fertile?
double the genome by mitotic non-disjunction (make allopolyploids)
what is the significance of polyploids in agriculture?
bigger fruits
seedless (sterile)
ei: bananas and strawberrys
what are the cons of polyploids in agriculture?
no evolution or natural selection, cannot adapt to new conditions
