Chapter Fourteen: Chromosomal Rearrangements Flashcards
(142 cards)
1
Q
two events that reshape genomes
A
- rearrangements
- changes in chromosome number
2
Q
DNA sequences are reorganized within one or more chromosome
A
chromosomal rearrangement
3
Q
loss or gain of entire chromosomes or sets of chromosomes
A
changes in chromosome number
4
Q
karyotypes usually remain ___ within a species
A
constant
5
Q
most genetic imbalances result in a ___
A
selective disadvantage
6
Q
related species usually have ___ karyotypes
A
different
7
Q
closely-related species differ by ___
A
a few rearrangements
8
Q
distantly-related species differ by ___
A
many rearrangements
9
Q
there is a correlation between karyotypic rearrangements and ___
A
speciation
10
Q
four types of chromosomal rearrangements
A
- deletion
- duplication
- inversion
- reciprocal translocation
11
Q
rearrangements that add or remove base pairs
A
deletion and duplication
12
Q
rearrangements that relocate chromosomal regions without changing the number of base pairs
A
inversion and reciprocal translocation
13
Q
___ and ___ can cause all four types of rearrangement
A
DNA breakage and aberrant crossing over
14
Q
mistakes in rearranging antibody genes can lead to ___
A
cancer
15
Q
___ can detect large chromosomal rearrangements
A
fluorescent in situ hybridization (FISH)
16
Q
___ has probes specific for two different chromosomes to show chromosomal translocation
A
spectral karyotyping (SKY)
17
Q
___ is produced by using FISH probes for particular regions of chromosomes
A
multicolor banding
18
Q
what is the ultimate way to determine if any chromosomal rearrangements are present
A
sequencing
19
Q
in an organism with a deletion, ___ reads would be detected in that section; in an organism with a duplication, ___ reads would be detected in that section
A
fewer
more
20
Q
whole genome sequencing can detect all rearrangements because ___
A
it will point out sequences that are not normally next to each other
21
Q
the precise base pairs at which rearranged chromosome segments begin and end
A
rearrangement breakpoints
22
Q
rearrangement breakpoints can be identified by ___
A
PCR and sequencing
23
Q
PCR analysis for rearrangement breakpoints is ___ and ___
A
inexpensive and sensitive
24
Q
deletion on both chromosomes
A
deletion homozygosity
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homozygosity for deletions is often ___ or ___
lethal or harmful
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the effect of a homozygous deletion depends on ___ and ___
size of deletion and affected genes
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deletion on one chromosome
deletion heterozygosity
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deletion heterozygotes can have a mutant phenotype due to ___
gene dosage effects (haploinsufficiency)
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what is haploinsufficiency
only one functional gene does not produce enough protein for the normal phenotype
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in deletion heterozygotes cells become vulnerable to ___ that will impact the ___
mutations
remaining normal chromosome
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if a deletion heterozygote carries a recessive allele on the normal chromosome, the organism will display the ___ phenotype
recessive mutant
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deletions can be used to locate ___
genes
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examining the phenotype of a deletion heterozygote can tell you ___
where a specific gene is
34
if the phenotype of the gene is mutant, you know the gene must lie ___ the deleted region; if the phenotype is wild-type, you know the gene must lie ___ the deleted region
inside
outside
35
edits genes by precisely cutting DNA and then letting natural DNA repair take over
CRISPR
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___ form in the chromosomes of deletion heterozygotes
deletion loops
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recombination between homologs can occur only at regions of ___
similarity
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no ___ can occur within a deletion loop
recombination
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because of deletion loops, ___ will not be accurate
genetic map distances
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why do deletion loops form in deletion heterozygotes
genes on the normal homolog don't have a sequence to match up with on the chromosome with the deletion
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most duplications have ___ phenotypic consequences
no
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why do most duplications produce normal phenotypes
increased gene copy number or altered expression in new chromosomal environment
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homozygosity or heterozygosity for a duplication can be ___ or ___ depending on ___ and ___
lethal or harmful
size of duplication and affected genes
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unequal crossing over between duplicated regions on homologous chromosomes can result in ___ and ___ copy number
increased and decreased
45
repeats of a chromosomal region that lie next to each other, either in the same order or reverse order
tandem duplications
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repeats of a chromosomal region that are not next to each other
nonrandom duplications
47
nonrandom duplications can be on the ___ or ___ from the original copy
same chromosome or a different chromosome
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with some genes, an abnormal phenotype can be caused by an imbalance in ___
gene dosage
49
the ___ gene in drosophila is extremely dosage sensitive
notch+
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haploinsufficient and duplication heterozygotes for the notch+ gene have a ___
mutant phenotype
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in unequal crossing over, one chromosome ends up with a ___ and the other ends up with a ___
duplication
deletion
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most inversions result in ___
normal phenotype
53
two reasons inversions can result in an abnormal phenotype
1. inversion disrupts a gene
2. inversion takes place near regulatory sequences for other genes or near heterochromatin
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inversions can act as crossover ___
suppressors
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in inversion heterozygotes, no viable offspring are produced that carry chromosomes resulting from ___
recombination int he inverted region
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___ can produce inversions
chromosome breakage
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inversion in which the centromere is within the inverted segment
pericentric inversion
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inversion in which the centromere is not within the inverted segment
paracentric inversion
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___ form in inversion heterozygotes
inversion loops
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in an inversion loop, one chromosomal region rotates to conform to the ___
sequence of its homolog
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formation of inversion loops in meiosis allows the ___ of homologous regions
tightest possible alignment
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crossing over within the inversion loop produces ___
aberrant recombination chromatids
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paracentric and pericentric inversion heterozygotes both result in ___
reduced fertility
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in pericentric inversion heterozygotes, each recombinant chromatid ___, but each will be ___
has a centromere
genetically imbalanced
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zygotes formed from normal chromosomes with chromosomes with these recombinant chromatids will be ___
nonviable
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in paracentric inversion hetrozygotes, one chromosome ___ and the other ___
lacks a centromere
has two centromeres
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zygotes formed from normal chromosomes with chromosomes with these dicentric recombinant chromatids will be ___
nonviable
68
which is worse: pericentric or paracentric inversion
paracentric
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inversions act as crossover ___
suppressors
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only gametes that did not recombine with inversion loop are ___
viable
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crossover suppression is used to make ___
balancer chromosomes
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balancer chromosomes are used for ___
genetic analysis
73
balancer chromosomes have ___, ___ inversions
multiple, overlapping
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in balancer heterozygotes, no viable recombinant progeny will be produced because of ___
crossover suppression
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attach part of one chromosome to a non homologous chromosome
translocation
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parts of two nonhomologous chromosomes switch places
reciprocal translocation
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reciprocal translocations result in ___ of genetic material
no loss
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reciprocal translocations usually result in ___ phenotype
normal
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reciprocal translocations may result in mutant phenotype if breakpoint is ___
within or near a gene
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reciprocal translocations may result in decreased ___
fertility
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a reciprocal translocation is the genetic basis for chronic ___
myelogenous leukemia
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leukemia patients have too many ___
white blood cells
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in a translocation homozygote, chromosomes segregate ___ during meiosis I
normally
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is the breakpoints of a reciprocal translocation do not affect gene function, there are no ___ in homozygotes
genetic consequences
85
in a translocation heterozygote, the two haploid sets of chromosomes carry ___ arrangements of DNA
different
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chromosome pairing during prophase I of meiosis is maximized by formation of a ___
cruciform structure
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three chromosome segregation patterns are possible for translocation heterozygotes
1. alternate
2. adjacent-1
3. adjacent-2
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balanced gametes are produced only by ___ segregation
alternate
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in reciprocal translocation heterozygote, only the ___ segregation pattern results in viable progeny
alternate
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___ is observed in heterozygotes with reciprocal translocation
pseudolinkage
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translocation arising from breaks at or near the centromeres of two acrocentric chromosomes
robertsonian translocation
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in robertsonian translocations, the small chromosome may be ___
lost from the organism
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___ can arise from a robertsonian translocation between chromosomes 21 and 14
down syndrome
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any segment of DNA that evolves the ability to move from place to place within a genome
transposable elements (TE)
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Marcus Rhoades and Barbara McClintock inferred existence of TEs from genetic studies of ___
corn
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TEs have been found in ___
all organisms
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TEs were previously considered to be selfish DNA because they ___
carried no genetic information useful to the host
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it is now know that some TEs have evolved ___
functions beneficial to the host
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TE length ranges from ___ to ___
50bp to 10kb
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TEs can be present in ___copies per genome
hundreds of thousands
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discoverer of TEs
Barbara McClintock
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molting of corn kernels is caused by ___
movements of a TE into and out of pigment gene
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two types of TEs
1. retrotransposons
2. DNA transposons
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three types of retrotransposons
1. long interspersed elements (LINEs)
2. short interspersed elements (SINEs)
3. human endogenous retroviruses (HERVs)
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LINEs and SINEs have ___
poly-A tails
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HERVs have ___
long terminal repeats
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HERVs are similar in structure to ___
retroviruses
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retrotransposons move via ___
RNA intermediates
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LINEs and HERVs have a gene encoding ___
reverse transcriptase
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the reverse transcriptase gene is a clue that LINEs and HERVs ___
move via an RNA intermediate
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retrotransposons move via ___
RNA intermediates
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experiment done with ___ proved that retrotransposons move via RNA intermediates
Ty1 retrotransposon of yeast
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Ty1 with an intron was cloned into a ___
plasmid
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all new insertions of the Ty1 into the genome ___
lacked the intron
115
the intron must have been removed by ___
splicing from an RNA
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five steps of how an LTR retrotransposon moves
1. transcription of retrotransposons
2. synthesis of cDNA by reverse transcriptase
3. staggered cut made in genomic target site
4. retrotransposon cDNA inserts into target site
5. original copy remains while new copy inserts into another genomic location
117
TEs whose movement does not rely on an RNA intermediate
transposon
118
most DNA transposons contain ___ and ___
inverted repeats of 10-200bp long at each end and a gene encoding transposase
119
recognizes inverted repeats (IRs) and cuts at the border between the IR and genomic DNA
transposase
120
transposase catalyzes the movement of ___
DNA transposons
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genes often contain ___ copies of TEs
defective
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many TEs sustain ___ during the process of transpositions or after transposition
deletions
123
if a deletion removes the promoter for retrotransposon transcription, ___
it cannot generate the RNA intermediate for future movements
124
if the deletion removes one of the inverted repeats at the end of a transposon, ___
transposase will be unable to catalyze transcription
125
deletions can create ___ TEs that cannot ___
defective
transpose again
126
non-deleted TEs that can transpose on their own
autonomous TEs
127
defective TEs that require the activity of non-deleted copies for the TE for movement
nonautonomous TEs
128
TEs can disrupt ___ and alter ___
genes
genomes
129
TE insertion can result in an altered phenotype if ___ or ___
it is inserted within the coding region of a gene or if is inserted near a gene
130
TE associated alleles can be ___
unstable
131
TEs can trigger spontaneous ___
chromosomal rearrangements
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there can be ___ between two copies of the same TE pair
unequal crossing over
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transposition can cause gene ___
relocation
134
mutations in eye color of drosophila because of TE insertions depend on ___ and ___
which TE is inserted and where it is inserted
135
gene relocation due to transposition can occur when two copies of a TE integrate in ___
nearby locations on the same chromosome
136
alternative splicing of transposase gene limits ___
TE movement
137
one splice produces ___, another splice produces ___; these two compete to ___
transposase
repressor of transposition
bind to the inverted repeats
138
chromosome rearrangements are sources of ___
variation
139
genes at or near rearrangement breakpoints may have new ___ or be ___
patterns of expression
fused with another gene
140
transposable elements can alter ___ or ___
patterns of expression or inactivate a gene
141
sets of related genes with slightly different functions
gene families
142
gene families most likely arose from ___
gene duplications
