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genetics > chapter 10 part 1 > Flashcards

chapter 10 part 1 Flashcards

1
Q

genome content, chromosome number, and relative size/shape of each chromosome are __________________

A

species-specific

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2
Q

closely related species have _________ numbers of chromosomes

A

similar

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3
Q

do chromosomes occupy the same territory in each nucleus?

A

no

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4
Q

once confined to a territory, what happens to a chromosome

A

chromosome doesn’t leave until the M phase is initiated

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5
Q

what do chromosomes do within their territories

A

active and move, turn during transcription and DNA replication

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6
Q

how do chromosomes appear to be anchored to their territories?

A

by their centromeres

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7
Q

inter-chromosomal domains

A

regions between territories

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8
Q

what do inter-chromosomal domains act as?

A

channels for movement of proteins, enzymes, and RNA molecules

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9
Q

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

A

center of the nucleus

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10
Q

smaller, less gene-rich chromosomes are usually found where?

A

near periphery of nucleus

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11
Q

what do karyotypes allow for

A

recognition of abnormalities in chromosome number or structure
- also comparison between species

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12
Q

what elements can be easily identified in a karyotype

A
  • extra/missing chromosomes
  • rearrangements (insertions, deletions)
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13
Q

in situ hybridization

A

uses molecular probes (DNA/RNA sequences) labeled with fluorescent to detect their target sequences

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14
Q

first-generation methods used nucleotide probes labeled with

A

P32

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15
Q

fluorescent in situ hybridization (FISH)

A

use multiple fluorescently colored labeled so each labeled chromosome can be identified with different wavelengths

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16
Q

short arm of chromosome

A

p

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17
Q

long arm of chromosome

A

q

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18
Q

metacentric

A

centromere is near the middle of the chromosome

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19
Q

submetacentric

A

centromere is between the center and the tip

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20
Q

acrocentric

A

centromere is close to one end

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21
Q

telocentric

A

centromere is at tip of chromosome and there is no p arm

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22
Q

acentric

A

piece of DNA without a centromere

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23
Q

heterochromatin

A
  • more condensed
  • silenced genes (methylated)
  • stains darker
  • more repetitive DNA
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24
Q

euchromatin

A
  • less condensed
  • actively expression genes (acetylated)
  • stains lighter
  • less repetitive DNA
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25
Q

chromosome banding allows cytogeneticists

A

cytogeneticists can identify each chromosome in a karyotype

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26
Q

standard for human chromosome banding

A

G (Giemsa) banding - patterns distinct and reproducible

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27
Q

how many genes in human genome

A

22,000

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28
Q

2000 Giemsa bands

A
  • average of 11 genes/band (both light and dark)
  • assume all bands have equal number of genes
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29
Q

light Giemsa bands =

A

euchromatin

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30
Q

dark Giemsa bands =

A

heterochromatin

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31
Q

how are designations stated

A

1q3.2.3
- numbering begins at the centromere and progresses outward in each direction

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32
Q

chromosome nondisjunction

A

failure of homologous chromosomes or sister chromatids to separate as they normally do during cell division

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33
Q

what can chromosome nondisjunction result in

A
  • abnormalities in chromosome number (aneuploidy)
  • somatic cells: one daughter w extra chromosome (2n+1) and other missing (2n-1)
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34
Q

mitotic nondisjunction

A
  • if at 1st division (zygotic) all cells aneuploid
  • if later in development, aneuploid sectors in an organism
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35
Q

meiotic nondisjunction

A
  • aneuploid haploid organisms (n+/-1)
  • aneuploid gametes (n+/-1) leading to aneuploid zygotes
  • increased frequency if crossing-over fails
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36
Q

result of nondisjunction in germ-line cells

A

aneuploid gametes that can produce aneuploid zygotes

37
Q

nondisjunction in meiosis I results from

A

failure of homologs to separate

38
Q

gametes produced from nondisjunction in meiosis I

A

n+1 or n-1

39
Q

fusion of n+/-1 gametes with normal n gametes produces…

A

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

40
Q

nondisjunction in meiosis II results from

A

failure of sister chromatids to separate normally

41
Q

gametes produced from nondisjunction in meiosis II

A
  • 2 normal gametes
  • one (n+1)
  • one (n-1)
42
Q

what do changes in gene dosage lead to

A

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

43
Q

aneuploidy laters the dosage of what?

A

all the genes on the affected chromosome

44
Q

how much more product is produced in trisomies

45
Q

how much less product is produced in monosomies

46
Q

do animals or plants tolerate gene dosage changes more readily?

47
Q

do aneuploids usually survive?

48
Q

what trisomies are usually seen in newborn infants

A

13, 18, and 21

49
Q

can sex chromosomes have viable monosomies or trisomies in humans

50
Q

Pallister-Killian Syndrome

A

occurs due to presence of anomalous extra isochromosome 12p (short arm)

51
Q

isochromosome

A

unbalanced structural abnormality in which the arms of the chromosome are mirror images of each other

52
Q

what does Palliester-Killian syndrome lead to

A

development of Tetrasomy 12p

53
Q

symptoms of Pallister-Killian syndrome

A
  • hypotonia
  • intellectual disability
  • distinctive facial features
  • sparse hair
  • unusual skin coloring
  • birth coloring
54
Q

how is Pallister-Killian a mosaic condition

A

because not all cells have the extra isochromosome

55
Q

what do studies that monitor human pregnancies indicate

A

half of all conceptions spontaneously abort during the first trimester

56
Q

more than half of the spontaneously aborted pregnancies carry what?

A

abnormalities of chromosome number or structure

57
Q

research has identified a link between trisomy 21 and what?

A

advanced maternal age (anyone over 35)

58
Q

what are responsible for cognitive disabilities and heart abnormalities in trisomy 21?

A

small number of genes on chromosome 21

59
Q

DSCR (Down Syndrome Critical Region)

A

correlated with majority of DS symptoms

60
Q

DYRK

A

candidate gene known to produce dosage-sensitive learning defects in mice and flies, makes major contribution to down syndrome

61
Q

DSCAM gene in mice and fruit flies

A

has homolog associated with formation of the heart and nervous system

62
Q

Turner syndrome

A

monosomy of X chromosome with no second sex chromosome

63
Q

what does Turner syndrome produce

A

phenotypically sterile females

64
Q

SHOX gene in XO embryos

A

single copy of gene, which is not activated by dosage compensation, is insufficient to direct normal development (haploinsufficient)

65
Q

what does mosaicism result from

A

mitotic nondisjunction early in embryogenesis

66
Q

ex. of Turner syndrome and mosaicism

A

25-30% of cases occur in females mosaic w:
- 46 XX cells
- 45 XO cells
- 47 XXX cells

67
Q

uniparental disomy

A

both copies of homologous chromosome pair arise from same parent

68
Q

what was uniparental disomy first identified in connection with

A
  • Angelman syndrome
  • Prader-Willi syndrome
  • caused by deletion of a small region of chromosome 15
69
Q

possible mechanisms of uniparental disomy

A
  • same chromosome (15) undergoes nondisjunction in both sperm and egg - when they unit, produce ind. w/ 2 copies of chromosome 15 from only 1 parent
  • more often: nondisjunction occurs in one parent to produce gamete w/ 2 copies of chromosome - units with normal gamete to produce trisomic zygote - trisomy rescue
70
Q

trisomy rescue

A

one copy of trisomy chromosome is randomly ejected in one of the first mitotic divisions after fertilization
- if 2 copies retained by zygote are from same parent, uniparental disomy results

71
Q

polyploidy

A

presence of 3+ whole sets of chromosomes in the nucleus of an organism

72
Q

autopolyploidy

A

duplication of chromosome sets within species

73
Q

polyploidy in plants typically increases

A

fruit and flower size

74
Q

allolpolyploidy

A

combining chromosome sets of different species

75
Q

what do allolpolyploids result in

A

interspecific hybrid offspring that is infertile because the chromosome sets are not homologous

76
Q

allopolyploidy involves sets of ________ homologous chromosomes

A

partially - homologous

77
Q

how can a hybrid be fertile in allolpolyploidy

A

chromosome nondisjunction leads to cells with double the number of chromosomes, so now each chromosome has homolog for pairing

78
Q

how do allopolyploids occur

A

naturally or via human manipulation

79
Q

fertility is decreased in _____-numbered polyploids

A

odd (3n, 5n)

80
Q

hybrid vigor

A

more rapid growth, increased fruit/flower production, improved resistance to disease of polyploids

81
Q

Triticum aestivum

A
  • bread wheat (2n = 42) = natural allolpolyploid
  • appears to be hexaploid (6x=42) = six sets of similar chromosomes from at least 3 separate varieties
82
Q

what are commercial bananas and seedless watermelons

83
Q

plant monoploids can be induced to grow from what?

A

1n cells in anthers

84
Q

G. Karpechencko

A

wanted plant with cabbage leaves and radish roots to solve world hunger

85
Q

cabbage leaves/radish root plants

A
  • each species has 18 chromosomes
  • induced fusion of gametes generated sterile hybrids
  • eventually produces seeds, had 36 chromosomes
86
Q

why did the cabbage/radish plant have 36 chromosomes

A

derived from spontaneous doubling of chromosome number which allows proper pairing at meiosis

87
Q

amphidiploid

A

interspecific hybrid having a complete diploid chromosome set from each parent form

88
Q

what is amphidiploid also called

A

allotetraploid (doubled diploid)

genetics (47 decks)

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