Variation in Chromosome Number Flashcards
ploidy number
number before n is the number of sets of chromosomes
aneuploidy
number of chromosomes in an interphase somatic cell is not an exact multiple of the haploid number
2n -1 = 7
monosomic
2n-2 = 6
nullisomic
2n-1-1 = 6
double monosomic
2n+1 =9
trisomic
2n + 2 =10
tetrasomic
2n+1+1 = 10
double trisomic
47 chromosomes
XXY
Klinefelter
47 chromosomes 21+
down syndrome
45 chromosomes
XO
turner
47 chromosomes
18+
edward
47 chromosomes
XXX
female
47 chromosomes
13+
Patau
polyploidy
extra sets of chromosomes
what are some examples of polyloids?
wheat oats cotton potatoes sugar salamanders frogs lizards
haploid
1 of every chromosome
diploid
2 of every chromosome
triploid
3 of every chromosome
tetraploid
4 of every chromosome
autopolyploidy
extra sets of chromsomes are identical to normal chromosome set
all sets are from the same species
tend to be sterile
allopolyploidy
combination of sets of chromosomes from 2 species
tend to be fertile
autotriploid
AAA
allotriploid
AAB
autotetraploid
AAAA
allotetraploid
AABB
nondisjunction in anaphase of mitosis
can result in doubling of chromosome number
relatively common in plants
nondisjunction of all chromosomes in meiosis
can result in gametes with extra sets of all chromosomes chromosomes
sterility in triploids
due to irregular pairing in meiosis that results in unbalanced gametes
difficult for 2 gametes that met at random to exactly restore 3 copies of each chromosome in a zygote
examples of triploids
bananas
seedless wtermelons
outcomes of meiosis in a triploid
a trivalent
or
a bivalent and a univalent
can an allotriploid for a trivalent
no
can an autotriploid form a trivalent
yes
fertility in autopolyploids
they are sterile to varying degrees
propagate asexually - ie cutting, suckers, etcs
examples of autopolyploids
potatoes
chrysanthemums
higher ploidy autopolyploids usually result in…
larger plants vigorous, lush vegetative parts flowers with multiple petal layers large flowers etc
meiotic possibility for autotetraploid
AAAA
2 bivalents
1 quadrivalent
1 univalent + 1 trivalent
liger
interspecific hybrid
female is fertile
male is sterile
both tiger and lion have 38 chromosomes
when can interspecific hybrids be fertile in animals?
when breeding occurs within the same genus or between sub-species
example of interspecific hybrid in animal that is sterile
why?
mule
Donkeys are 2n = 62
Horses are 2n = 64
Not all chromosomes have a homologous partner to allow balanced gametes
amphidiploid
allopolyploid that behaves like a diploid in meiosis
forms balanced gametes
how is an amphidiploid produced?
- 2 species with different ploidy numbers mate forming a sterile hybrid
- spontaneous doubling of the chromosomes occurs
- there are now two copies of each chromosome, create a fertile product
colchicine
- chemical that can cause chromosome doubling
- disrupts spindle fibers in cell division so that chromosomes do not segregate
- used to turn a sterile hybrid into a amphidiploid in the lab
Beasley
used colchicine to create a fertile amphidiploid from the combination of old world cotton and wild American cotton, discovering the progenitor species of modern day cotton
triticale
hybrid of wheat and rye then exposed to colchicine to create fertile product
hearty and better amino acid content