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chapter 10 part 1 Flashcards

1
Q

what things are species-specific about chomosomes?

A

chromosome size, number in a nucleus, & shape

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2
Q

what does each chromosome pair in a diploid genome have?

A

distinct size, shape, & genetic content

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3
Q

do all chromosomes occupy the same territory in each nucleus?

A

no

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4
Q

when does a chromosome leave the territory it has confined itself to?

A

once M phase is initiated

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5
Q

are chromosomes inactive in their territories?

A

no, they are active within their territories & move, & turn during transcription & DNA replication

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6
Q

what do chromosomes appear to be anchored in their territories by?

A

their centromeres

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7
Q

what are the regions between territories called?

A

inter-chromosomal regions

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8
Q

what are inter-chromosomal regions?

A

channels for movement of proteins, enzymes, & RNA molecules

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9
Q

where are larger, more gene-rich chromosomes generally found?

A

more towards the center of the nucleus, while the smaller ones with fewer genes are near the periphery

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10
Q

what do karyotypes allow for?

A

recognition of abnormalities in chromosome number or structure
-autosomes are numbered one through 22 in their descending order of size

-extra or missing chromosomes can be identifies as well as rearrangements (insertions or deletions)
-comparison between species (allows for tracing of evolutionary history of related species)

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11
Q

what does in situ hybridization use to detect their target sequences

A

molecular probes (DNA or RNA) labeled with flouresence
-multiple fluorescent labels so that each labeled chromosome can be identified with different wavelengths

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12
Q

what did first generation methods of in situ hybridization use

A

nucleotide probes labeled with P32

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13
Q

what does FISH stand for

A

fluorescent in situ hybridization

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14
Q

short arm

A

p

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15
Q

long arm

A

q

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16
Q

metacentric

A

the centromere is near the middle of the chromosome

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17
Q

submetacentric

A

the centromere is between the center & the tip of the chromosome

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18
Q

acrocentric

A

the centromere is close to one end of the chromosome

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19
Q

acentric

A

a piece of DNA without a centromere

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20
Q

telocentric

A

the centromere is at the tip of the chromosome & there is no p arm

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21
Q

heterochromatin

A

more condensed
silenced genes (methylated)
stains darker
more repetitive DNA

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22
Q

euchromatin

A

less condensed
actively expressing genes (acetylated)
stains lighter
less repetitive DNA

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23
Q

what does chromosome banding allow

A

cytogeneticists to identify each chromosome in a karyotype

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24
Q

what is the standard for human chromosome banding?

A

G (giesma banding)

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25
human genome has how many genes & how many giesma bands
22,000 genes & 2000 giesma bands
26
how many genes per band
11 genes per pand
27
chromosome nondisjunction
the failure of homologous chromosomes or sister chromatids to separate as they normally do during cell division (mitosis or meiosis)
28
what can chromosome nondisjunction result in
abnormalities in chromosome number (aneuploidy) -in somatic cells, it results in one daughter cell w an extra chromosome (2n+1) & the other with a missing one (2n-1)
29
mitotic nondisjunction
if at first division (zygotic) all cells are diploid if later in development, aneuploid sectors in an organism
30
meiotic nondisjunction
-aneuploid haploid organisms (n+- 1) -aneuploid gametes (n +-1) leading to aneuploid zygotes -increased frequency if crossing over fails
31
results on nondisjunction in germ-line cells is what
aneuploid gametes that can produce aneuploid zygotes -results in failure of homologs to separate (the gametes produced are either n+1 or n-1)
32
what does fusion of non-disjunction in meiosis 1 gametes produce?
trisomic (2n+1) or monosomic (2n-1) offspring
33
nondisjunction is meiosis II
failure of sister chromatids to separate
34
aneuploidy
alters the dosage of all the genes on the affected chromosomes -50% less product in monosomics -50% more product in trisomics -most animals are highly sensitive to changes in gene dosage -plants tolerate gene dosage changes more readily
34
are plants or animals more sensitive to changes in gene dosage?
animals
34
how many gametes will be affected in nondisjunction of meiosis II
among the four gametes, only 2 will be affected -two normal -one (n+1) -one (n-1)
34
what do changes in gene dosage lead to
an imbalance of gene products from the affected chromosome relative to the unaffected chromosomes
35
are humans sensitive to changes in gene dosage?
yes, very humans usually do not survive aneuploidy
36
are autosomal monosomies observed in humans?
no- only one type of sex-chromosome monosomy even is viable
37
what trisomies are seen in newborn infants
trisomies: 2n+1 trisomies of chromosome 13, 18, & 21 (autosomes)
38
what does pallister-killian syndrome occur due to the presence of?
anomalous extra isochromosome 12p, the short arm of the 12th chromosome
39
what does the presence of the isochromosome lead to?
development of tetrasomy 12p
40
what type of condition is pallister-killian syndrome?
a mosaic condition -not all cells have the extra isochromosome
41
about how many pregnancies sel abort
half
42
how much of spontaneously aborted pregnancies carry abnormalities of chromosome number of structure?
more than half
43
what is trisomy 21
down syndrome
44
what is the link of trisomy 21 that researchers have found?
a link between risk of trisomy 21 & maternal age
45
what is the age that is considered (advanced maternal age)
35
46
what portion of the chromosome can be correlated with the majority of down syndrome symptoms?
DSCR- down syndrome critical region
47
what gene made a major contribution to down syndrome that is known to produce dosage-sensitive learning defects in mice & flies
DYRK
48
what gene has a homolog in mice & fruit flies that is associated with formation of the heart & nervous system
DSCAM
49
turner syndrome
a monosomy of the X chromosome with no second chromosome (X0) -embryo survives but has developmental abnormalities -phenotypically sterile females with other characteristics abnormalities
50
what gene in turner syndrome, which is not inactivated by dosage compensation, is insufficient to direct normal development
SHOX - haploinsufficiency of this gene plays central role in producing the symptoms of the syndrome
51
how can mosaicism develop
as a result of mitotic disjunction early in embryogenesis
52
UPD
uniparental disomy (UPD) -both copies of homologous chromosome pair arise from the same parent
53
what was UPD first identified in
angelman syndrome & prader-willi syndrome -usually caused by deletion of a small region of chromosome 15
54
which actors son has a uniparental disomy
colin farrell's son has angelman syndrome
55
possible mechanisms of UPD
-in rare cases, the same chromosome- for instance, chromosome 15- undergoes nondisjunction in both sperm & egg -when these gametes unite, they produce an individual with two copies of chromosomes 15 from one parent & non from the other
56
what produces a trisomic zygote
when a nondisjunction occurs in one parent, resulting in a gamete with two copies of the chromosome (n+1) unites with a normal gamete
57
what happens in trisomy rescue
one copy of the trisomy chromosome is randomly ejected in one of the first mitotic divisions after fertilization
58
if two copies retained by the zygote are from the same parent, what results?
uniparental disomy
59
polyploidy
the presence of three or more whole sets of chromosomes in the nucleus of an organism
60
what can polyploidy result from
-a duplication of chromosome sets within a species (autopolyploidy) -combining the chromosome sets of different species (allopolyploidy)
61
what does polyploidy in plants do?
increases fruit size
62
allopolyplody
carry multiple sets of chromosomes that originate in different species
63
what does allopolyploudy result in
in intERspecific hybird offsprig that is infertile because the chromosome sets are not homologous
64
homeologous
partially homologous chromosomes
65
what involved homelogous chromosomes
allopolyploidy
66
chromosome nondisjuction in allopolyploidy can lead to what
-cells with double the number of chromosomes so that now each chromosome has a homolog for pairing, & then the hybrid is fertile
67
how to allopolyploids occur
both naturally & by human manipulation -fruit & flower size increased by polyploids -fertility is decreased (mainly in odd number diploids) -hybrid vigor, more rapid growth, increased fruit & flower production, improved resistance to disease occurs
68
triticum aestivum
bread wheat (2n=42) natural allopolyploid (n=21) -appears to be hexaploid (6x=42) ---six sets of similar chromosomes from at least three separate varieties
69
agricultural applications of allopolyploidy
-plant monoploids can be induced to grow from 1n cells in anthers -commercial bananas (3n=33), & seedless watermelons are triploids - no seeds
70
who wanted cabbage laves with leaves & radish roots
G. karepechencko
71
amphidiploid
an interspecific hybrid having a complete diploid chromosome set from each parent form also called alleotetraploid (doubled diploid)

genetics (37 decks)

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