Chapter Fifteen: Ploidy Flashcards
many plants and some animals can tolerate having multiple ___
chromosome sets
more than two sets of chromosomes
polyploidy
three sets of chromosomes
triploidy
complete chromosome set
euploid
missing one or more chromosomes from a set, or have extra chromosomes
aneuploid
calculation for euploidy
2n
an individual lacking one chromosome
monosomy
an individual with one extra chromosome
trisomy
calculation for nullisomy
2n-2
calculation for monosomy
2n-1
calculation for trisomy
2n+1
aneuploidy usually results in ___ or ___
multiple abnormalities or lethality
autosomal monosomy is usually ___
lethal
most trisomies are ___, a few result in ___
lethal
characteristic syndromes
sex chromosome aneuploidy is ___ due to ___
tolerated
X-chromosome inactivation
___ of births have some sort of genetic anomaly
0.4% (1/250)
phenotype of X-chromosome aneuploidy is largely due to ___ genes
pseudoautosomal (PAR)
X-chromosome aneuploidy causes ___
infertility
aneuploidy is caused by ___
nondisjunction
nondisjunction is the failure of chromosomes to ___
segregate normally
when can nondisjunction occur
meiosis I, meiosis II, and mitosis
failure of sister chromatids to separate during anaphase of mitosis
mitotic nondisjunction
lagging chromatid that is not pulled to either spindle pole at mitotic anaphase
chromosome loss
true or false: nondisjunction can occur in meiosis I, meiosis II, and mitosis
true
aneuploid cells can survive and undergo ___, producing ___
further rounds of mitosis
clones of aneuploid cells
there can be side-by-side existence of ___ cells and ___ cells
normal and aneuploid
drosophila that has equal parts male and female tissue after loss of X chromosome in first mitotic division
gynandromorph
are all euploid species diploid
no
the number of chromosomes in a single, complete set
basic chromosome number (x)
for diploid species, x = n = ___
the number of chromosomes in the gametes
for polyploid species, X ___ n
does not equal
bread wheat has 42 chromosomes: 6 nearly identical sets each containing 7 chromosomes
therefore: x=___, 6= ___, and n=___
7
42
21
monoploid and polyploidy are ___ observed in animals
rarely
polyploidy in humans is ___
lethal
can create monoploid plants from ___ species with special treatment of ___
diploid
germ cells
treated cells divide into a mass called an ___
embryoid
subsequent exposure to ___ enables the embryoid to develop into a monoploid plant
plant hormones
monoploid plants may also arise from rare ___ in large, natural populations
spontaneous events
4 uses of monoploid plants
- visualize recessive traits directly, without crosses to homozygosity
- introduce mutations into individual monoploid cells
- select for desirable phenotypes (like herbicide resistance)
- hormone treatment to grow cells into monoploid cells
___ prevents spindle formation and results in doubling of chromosome numbers
colchicine treatment
colchicine is good for ___ to observe chromosomes for things like karyotyping
metaphase arrest
triploid plants result from the union of ___ and ___
monoploid and diploid gametes
diploid gametes may arise from a ___ parent or from a diploid with ___
4x
defects in meiosis
meiosis in a triploid organism will almost always be ___, with ___ of some chromosomes and ___ of others
unbalanced
two copies
one copy
fertilization with gametes for triploid organisms usually produces ___
unviable offspring
if ___, occasionally a meiosis of triploid organisms will produce balanced gametes
X is small
tetraploid cells occur during mitosis in a diploid when ___
chromosomes fail to separate into two daughter cells
if tetraploidy occurs in gamete precursors, ___ are produced
diploid gametes
union of two ___ produces a tetraploid organism
diploid gametes
polyploids in which all chromosome sets are derived from the same species
autopolyploid
pairs of synapsed homologous chromosomes
bivalents
in a tetraploid, pairing of chromosomes as bivalents results in ___
balanced genes
tetraploids generate ___ mendelian ratios
unusual
___ of all known flowering plant species are polyploid
1/3
polyploidy often results in increased ___ and ___ in plants
size and vigor
many polyploid plants have been selected for ___
agricultural cultivation
hybrids in which chromosome sets come from distinct, but related species
allopolyploid
all-polyploids are usually ___ because different chromosomes sets cannot easily ___
infertile
pair and segregate properly
type of allopolyploid produced by mating of two different diploid parental species
amphidiploid
sterile F1 from crossing cabbages and radishes
raphanobrassica
F1 hybrid of wheat and rye, allopolyploid
triticale
duplication of whole genomes are useful for ___
evolution
plant biologists think that around 90 million years ago, an ancient diploid plant with 5 chromosomes underwent a ___
whole genome duplication
in the rice genome, many blocks of ___ are found on two different chromosomes
homologous gene sequences
