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Genetics 1 > Topic 7: Chromosome Alterations > Flashcards

Topic 7: Chromosome Alterations Flashcards

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1
Q

___________: contain a single chromosome within an arbitrary region that is not bound by any membranes

A

chromosomal territories

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2
Q

how do we visualize our chromosomes?

A

with a karyotype! (an individual’s complete set of chromosomes- can now be made into a picture!)

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3
Q

chromosomes 1-22 are ________

A

autosomes

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4
Q

chromsome 23 is a ___________

A

sex chromosome (X or Y)

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5
Q

chromosomes are divided at the centromere into _______________

A

chromosome arms (usually unequal lengths)

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6
Q

short arm = (________)

A

p arm

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7
Q

long arm = (________)

A

q arm

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8
Q

_________ chromosomes have a centromere near the middle

A

metacentric

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9
Q

______ chromosomes have a centromere nearer to one end

A

submetacentric

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10
Q

_________ chromosomes have centromeres at one end

A

acrocentric

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11
Q

_________ chromosomes have a terminal centromere

A

telocentric

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12
Q

________ condensation results in the banding patterns on chromosomes

A

chromatin

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13
Q

_______: regions of lesser compaction, actively transcribed chromatin

_________: regions of higher compaction, less gene transcription

A

euchromatin

heterochromatin

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14
Q

_________: when chromosomes and sister chromatids fail to separate properly

A

nondisjunction

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15
Q

chromosome numbers that are a multiple of the haploid number (2n, 3n, 4n…) are ______

A

euploid

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16
Q

if we add or remove a chromosome, it alters the euploid number and generates an _______

A

aneuploid

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17
Q

____________in germ-line cells causes aneuploidy

A

nondisjunction

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18
Q

nondisjunction in germ-line cells results in the failure of homologous chromosome separation in ________

A

meiosis I

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19
Q

________ (2n+1): three of one chromosome instead of a homologous pair

A

trisomy (trisomic)

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20
Q

_______ (2n-1): a single copy of the chromosomes instead of a homologous pair

A

monosomic

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21
Q

nondisjunction in germ-line cells results in the failure of sister chromatid separation in _______

A

meiosis II (typically follows after a normal meiosis I)

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22
Q

aneuploidy alters gene dosage, which two men worked on this concept? and with what plant?

A

Albert Francis Blakeslee and John Belling worked on the Jimson Weed

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23
Q

true/false: aneuploidy changes the gene dosage of ALL the genes on the affected chromosome

A

true!

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24
Q

in diploid organisms, gene dosage is ____%
monosomic: ______%
trisomic: _________%

A

100
50
150

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25
Q

true/false: plants aren’t as tolerant to changes in gene dosage compared to animals

A

false! they are!

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26
Q

where are the three most common chromosomes for trisomy in humans? How many total opportunities for trisomy are there?

A

trisomy 13, 18, 21

potential for 24 different kinds of trisomy (often see them in sex chromosomes!!)

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27
Q

when does trisomy 21 (Down Syndrome) occur? in what meiotic stage?

what is trisomy 21 linked to?

A

reaches synapsis in prophase I, then stops (90% of trisomy 21 cases were a result of meiosis I nondisjunction)

linked to the age of the mother

children have two copies of maternal C21, and one copy of paternal C21

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28
Q

what are two examples of gene dosage differences in humans with missing/extra sex chromosomes? (female)

A

turner syndrome (X0)

triple X syndrome (XXX)

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29
Q

X-inactivation mosaicism occurs from ______ nondisjunction: occurs during embryogenesis early in development

A

mitotic (example: Turner syndrome)

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30
Q

____________ disomy: both copies of the homologous chromosome pair are derived from the same parent

A

uniparental (requires nondisjunction of the same chromosome in both the eggs and the sperm!! (super rare!!))

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31
Q

________: the presence of three or more sets of chromosomes

A

polyploidy (very common in plants!!)

32
Q

________: have chromosomes derived from a single species

A

autopolyploids

33
Q

______: have chromosomes derived from multiple species

A

allopolyploids

34
Q

polyploidy results from….

A

meiotic nondisjunction (2n egg + 1n sperm)

mitotic nondisjunction (doubles chromosome number)

35
Q

what are the consequences of commercial polyploidy in food?

A

fruit and flower size increases, reduced fertility (seedless fruits), increase in heterozygotes relative to diploids

36
Q

development of wheat: the union of diploid genomes of _____ ancestral species

A

three

37
Q

true/false: changes to chromosome structure can result in the loss/addition of genes

A

true! causes gene dosage imbalances, animals are greatly affected by these abnormalities

38
Q

why are chromosome mutations important?

A

a common source of genetic variation, a major cause of genetic disorders and conditions, a cause of infertility

39
Q

what are the main four kinds of mutations?

A

deletions, duplications, inversions, translocations

40
Q

what are three things that can lead to chromosome breaks during DNA synthesis/crossing over in meiosis?

A

external mutagens/chemicals/radiation
transposable bits of DNA (mobile)
recombination errors

41
Q

true/false: when a break happens, segments of the chromosome can be lost

A

true

42
Q

partial chromosome deletion: both strands of DNA are severed at the _____________

A

chromosome breakpoint (they retain their chromatin structure, can re-adhere to each other)

43
Q

______ deletion: chromosome end breaks off, containing telomere and additional genetic material

A

terminal deletion

44
Q

terminal deletion leaves a chromosome fragment ______

A

acentric (without a centromere)

45
Q

cri-du-chat syndrome results in a partial __________

A

partial deletion heterozygote (one chromosome is wildtype, and the homolog has a terminal deletion)

46
Q

_____________: The pattern of inheritance in which a single recessive allele is inherited but is still expressed

A

pseudodominance

47
Q

________ syndrome displays pseudodominance because the allele on the normal homolog will be phenotypically expressed, instead of the partial deletion

A

cri-du-chat

48
Q

_________ deletion: two chromosomal breaks, resulting in the loss of an internal segment

A

interstitial deletion (results in a shorter than normal chromosome)

49
Q

what is the human example of interstitial deletion?

A

WAGR syndrome

50
Q

if a segment is deleted from both homologous chromosomes, it is a _______

A

deletion homozygote

51
Q

_________- are repeated segments on a chromosome, can arise form unequal crossing over

A

duplications

52
Q

unequal crossovers result in what two main categories?

A

partial duplication
partial deletion

53
Q

an individual with one wildtype chromosome and one with duplicated material is a partial _________

A

duplication heterozygote

54
Q

true/false: unequal crossover isn’t rare and occurs when homologs misalign during prophase I

A

false! it is rare!

55
Q

what is an example of human duplications?

A

Williams-Beuren syndrome

56
Q

in Williams-Beuren syndrome, what are the effects of the shortened partial deletion chromosome? the lengthened partial duplication chromosome?

A

shortened: causes the phenotypic effects in the disorder
lengthened: has no negative phenotypic effects

57
Q

how do we detect deletions and duplications? two ways

A

using a microscope, can usually see them if they’re 100 000- 200 000 basepairs or more

look for unpaired loops

58
Q

how/when do unpaired loops form?

A

form during the mismatch of homologous pairs during prophase I

59
Q

when do chromosome inversions happen?

A

when two “sticky ends” join back to the broken chromosome, but in the wrong orientation

60
Q

__________ inversion: beside the centromere

A

paracentric inversion (doesn’t include the centromere)

61
Q

_________ inversion: around the centromere

A

pericentric inversion (includes the centromere)

62
Q

_________ heterozygotes have one wildtype chromosome and one inverted chromosome

A

inversion heterozygotes

63
Q

true/false: inversions usually only affect one member of the homologous pair

A

true!

64
Q

________: has two centromeres

A

dicentric

65
Q

_______: has no centromeres

A

acentric

66
Q

during ___________, a dicentric bridge forms as the dicentric chromosome is pulling towards both poles of the cell (breaking it due to tension)

A

anaphase I

67
Q

in a pericentric inversion, crossing over occurs…

A

inside the region of the inversion loop

68
Q

inversions create _______ suppression

A

crossover suppression

69
Q

when a chromosome breaks and the fragment reattaches to a different chromosome, or to a new spot on the same chromosome, ________ has occurred

A

translocation

70
Q

________ heterozygotes have one wildtype chromosome and one altered chromosome

A

translocation

71
Q

_________ translocation: reattachment to a new chromosome (a one-way event)

A

unbalanced

72
Q

_________ translocation: two chromosome swap fragments with each other (a two-way event)

A

reciprocal

73
Q

________ translocation (chromosome fusion): two nonhomologous chromosomes fuse together, with the loss of one of the centromeres

A

Robertsonian translocation

74
Q

_____________: will move chromosomes I and IV to one poles, and II and III to the other pole

A

alternate segregation

75
Q

________: will move chromosomes I and III to one pole, and chromosomes II and IV to the other

A

adjacent segregation

76
Q

________ are associated with many types of cancer, and genomic instabilities

A

translocations

Genetics 1 (11 decks)

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