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genetics > chapter 10 part 1 > Flashcards

chapter 10 part 1 Flashcards

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Biology 101 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
Q

human genome has how many genes & how many giesma bands

A

22,000 genes & 2000 giesma bands

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26
Q

how many genes per band

A

11 genes per pand

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27
Q

chromosome nondisjunction

A

the failure of homologous chromosomes or sister chromatids to separate as they normally do during cell division (mitosis or meiosis)

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28
Q

what can chromosome nondisjunction result in

A

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)

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29
Q

mitotic nondisjunction

A

if at first division (zygotic) all cells are diploid
if later in development, aneuploid sectors in an organism

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30
Q

meiotic nondisjunction

A

-aneuploid haploid organisms (n+- 1)
-aneuploid gametes (n +-1) leading to aneuploid zygotes
-increased frequency if crossing over fails

31
Q

results on nondisjunction in germ-line cells is what

A

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
Q

what does fusion of non-disjunction in meiosis 1 gametes produce?

A

trisomic (2n+1) or monosomic (2n-1) offspring

33
Q

nondisjunction is meiosis II

A

failure of sister chromatids to separate

34
Q

aneuploidy

A

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
Q

are plants or animals more sensitive to changes in gene dosage?

A

animals

34
Q

how many gametes will be affected in nondisjunction of meiosis II

A

among the four gametes, only 2 will be affected
-two normal
-one (n+1)
-one (n-1)

34
Q

what do changes in gene dosage lead to

A

an imbalance of gene products from the affected chromosome relative to the unaffected chromosomes

35
Q

are humans sensitive to changes in gene dosage?

A

yes, very
humans usually do not survive aneuploidy

36
Q

are autosomal monosomies observed in humans?

A

no- only one type of sex-chromosome monosomy even is viable

37
Q

what trisomies are seen in newborn infants

A

trisomies: 2n+1
trisomies of chromosome 13, 18, & 21 (autosomes)

38
Q

what does pallister-killian syndrome occur due to the presence of?

A

anomalous extra isochromosome 12p, the short arm of the 12th chromosome

39
Q

what does the presence of the isochromosome lead to?

A

development of tetrasomy 12p

40
Q

what type of condition is pallister-killian syndrome?

A

a mosaic condition
-not all cells have the extra isochromosome

41
Q

about how many pregnancies sel abort

A

half

42
Q

how much of spontaneously aborted pregnancies carry abnormalities of chromosome number of structure?

A

more than half

43
Q

what is trisomy 21

A

down syndrome

44
Q

what is the link of trisomy 21 that researchers have found?

A

a link between risk of trisomy 21 & maternal age

45
Q

what is the age that is considered (advanced maternal age)

A

35

46
Q

what portion of the chromosome can be correlated with the majority of down syndrome symptoms?

A

DSCR- down syndrome critical region

47
Q

what gene made a major contribution to down syndrome that is known to produce dosage-sensitive learning defects in mice & flies

A

DYRK

48
Q

what gene has a homolog in mice & fruit flies that is associated with formation of the heart & nervous system

A

DSCAM

49
Q

turner syndrome

A

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
Q

what gene in turner syndrome, which is not inactivated by dosage compensation, is insufficient to direct normal development

A

SHOX
- haploinsufficiency of this gene plays central role in producing the symptoms of the syndrome

51
Q

how can mosaicism develop

A

as a result of mitotic disjunction early in embryogenesis

52
Q

UPD

A

uniparental disomy (UPD)
-both copies of homologous chromosome pair arise from the same parent

53
Q

what was UPD first identified in

A

angelman syndrome & prader-willi syndrome
-usually caused by deletion of a small region of chromosome 15

54
Q

which actors son has a uniparental disomy

A

colin farrell’s son has angelman syndrome

55
Q

possible mechanisms of UPD

A

-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
Q

what produces a trisomic zygote

A

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
Q

what happens in trisomy rescue

A

one copy of the trisomy chromosome is randomly ejected in one of the first mitotic divisions after fertilization

58
Q

if two copies retained by the zygote are from the same parent, what results?

A

uniparental disomy

59
Q

polyploidy

A

the presence of three or more whole sets of chromosomes in the nucleus of an organism

60
Q

what can polyploidy result from

A

-a duplication of chromosome sets within a species (autopolyploidy)
-combining the chromosome sets of different species (allopolyploidy)

61
Q

what does polyploidy in plants do?

A

increases fruit size

62
Q

allopolyplody

A

carry multiple sets of chromosomes that originate in different species

63
Q

what does allopolyploudy result in

A

in intERspecific hybird offsprig that is infertile because the chromosome sets are not homologous

64
Q

homeologous

A

partially homologous chromosomes

65
Q

what involved homelogous chromosomes

A

allopolyploidy

66
Q

chromosome nondisjuction in allopolyploidy can lead to what

A

-cells with double the number of chromosomes so that now each chromosome has a homolog for pairing, & then the hybrid is fertile

67
Q

how to allopolyploids occur

A

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
Q

triticum aestivum

A

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
Q

agricultural applications of allopolyploidy

A

-plant monoploids can be induced to grow from 1n cells in anthers
-commercial bananas (3n=33), & seedless watermelons are triploids - no seeds

70
Q

who wanted cabbage laves with leaves & radish roots

A

G. karepechencko

71
Q

amphidiploid

A

an interspecific hybrid having a complete diploid chromosome set from each parent form
also called alleotetraploid (doubled diploid)

genetics (23 decks)

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