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Genetics > 7. Chromosomal Alterations > Flashcards

7. Chromosomal Alterations Flashcards

1
Q

Chromosomal territories

A

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

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2
Q

Karyotype

A

A way to view our chromosomes

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3
Q

Autosomes

A

Chromosome 1-22

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4
Q

Sex chromosome

A

Chromosome 23

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5
Q

Sections of chromosomes

A
  • Chromosomes are divided at the centromere and create CHROMOSOME ARMS (short arm (p), long arm (q))
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6
Q

Metacentric chromosomes

A

centromere is in the middle

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7
Q

submetacentric chromosomes

A

centromere nearer to one end

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8
Q

acrocentric chromosomes

A

centromeres at one end

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9
Q

telocentric chromosomes

A

terminal centromere - no arm

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10
Q

Euchromatin

A

regions of lesser compaction, actively transcribed

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11
Q

Heterochromatin

A

regions of higher compaction, less gene transcription

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12
Q

Nondisjunction in chromosomes, euploid and anueploid

A
  • adds or removes large amounts of genetic material - alters the phenotype and affects development and/or fertility
  • euploid: chromosome numbers that are a multiple of the haploid
  • aneuploid: add or removing a chromosome and affecting the euploid
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13
Q

Nondisjunction in Meiosis I

A

failure of chromosome separation and causes trisomic (three of one chromosome instead of a pair)
monosomic (single copy of chromosome instead of pair)

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14
Q

Nondisjunction in Meiosis II

A

failure of sister chromatid separation and causes trisomic or monosomic

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15
Q

Blakeslee and Belling

A

identified 12 phenotypically distinct lines of a plant based on anueploidy and it altering gene dosage

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16
Q

Gene dosage percentages

A

normal: 100%
monosomic: 50%
trisomic: 150%

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17
Q

Trisomy 21

A

Down syndrome
- meiosis begins in the fetus ovaries and pauses until puberty and egg is released into fallopian tubes
- caused by meiosis 1 nondisjunction because the pause is so long
- 2 copies of mom and 1 copy of dad

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18
Q

Turner Syndrome

A

X0 females
- Lack of 2 X chromys
- need 2 to develop so lack of 1 results in no secondary characteristics, infertility, short stature, webbed neck
- rare in males

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19
Q

Triple X Syndrome

A

XXX Females
- tall, reduction in fertility, menstrual issues, speech delays

20
Q

Mosaicism

A

one x chromosome in female somatic cells is randomly inactivated
due to nondisjunction in mitosis during embryogenesis

21
Q

Uniparental distomy

A

-Both copies of the homologous chromosome pair are derived from the same parent.
- Ex) Angelman syndrome, prader-willi syndrome
- Rare because it requires nondisjunction of the same chromsome in both egg and sperm
-

22
Q

Trisomy rescue

A
  • Non-disjunction in one parent contributing 2 copies + 1 other parental = 3.
  • the extra copy can be tossed out during embryonic development
23
Q

Types of polyploids and how they happen

A

Autopolyploids: chromosomes derived from a single species
Allopolyploids: chromosomes derived from multiple species
- Meiotic and mitotic nondisjunction

24
Q

Consequences of polyploid

A
  • size of fruit and flower increases, reduced fertility, increase in heterozygotes (hybrids)
25
Q

Deletions

A
  1. Partial: both strands of DNA are severed at break point, they can re-adhere but breakage can lead to partial deletion of genes
  2. Terminal: the entire arm breaks off and no centromere
26
Q

Example of deletion

A

Cri-du-chat: cat cry sound, mental impairment - caused by terminal deletion on chromosome 5.

27
Q

partial deletion heterozygote

A

one chromosome is wildtype and homolog has terminal deletion

28
Q

pseudodominance

A

normal recessive homolog and homolog with terminal deletion

29
Q

interstitial deletion and example

A
  • 2 chromosomal breaks, broken ends can reattach theyll just be shorter
  • WAGR and WAGRO
30
Q

Deletion homozygote

A

segment is deleted from both homologous chromosomes

31
Q

Duplications and how they arise,

A
  • repeated segments on chromosome
  • result from unequal crossing over
32
Q

Williams-Beuren syndrome

A
  • partial deletion heterozygotes on chromosome 7
    -shortened causes disorder, lengthened has no affect
33
Q

How to detect duplications

A
  • microscope or unpaired loops
34
Q

Inversion

A
  • when sticky ends attach back to the chromosome but wrong orientation
35
Q

paracentric inversion

A

beside the centromere, not including the centromere, occurs in single arm
- resulting in 1 wildtype, 1 inverted, 2 recomb, dicentric (2 centromeres), acentric (no centromere)

36
Q

pericentric inversion

A

around the centrimere, including centromere, rotates on the centromere
- resulting in 1 wildtype, 1 inverted, 2 recombinants (deletions, duplicated)
- produces 2 viable gametes

37
Q

do inversion homozygotes and heterozygotes still have all genes

A
  • homo: yes unless inversion break disrupts a coding region, position along the chromosome affects gene expression
  • het: yes but inversion is mismatched
37
Q

inversion heterozygotes

A

one wildtype and and one inverted

38
Q

Important inversion implications

A
  1. Probability of crossover within the inversion loop is linked to the size of the inversion loop - small inversion = small loops
  2. Supresses the production of recombinant chromosome - crossover supression (no recombinant chromosomes)
  3. Fertility may be altered if an inversion heterozygote carries a larger inversion
39
Q

Translocation

A

When a chromosome breaks and the fragment reattaches to a different chromosome or to a new spot on the same chromosome

40
Q

Translocation heterozygotes

A

one wildtype chromosome and one altered chromosome

41
Q

Unbalanced translocation

A

reattachment to a new chromosome

42
Q

Reciprocal translocation

A

2 chromosomes swap fragments with each other - down syndrome

43
Q

Robertsonian translocation

A

2 nonhomologous chromosomes fuse together, with the loss of one of the centromeres

44
Q

Alternate segregation

A

moves chromosomes I and IV to opposite poles and II and III to opposite poles

45
Q

Adjacent segregation

A

moves chromosomes I and III to opposite poles and II and IV to opposite poles

46
Q

Why are translocations important

A
  • associated with many types of cancer (interrupts a gene required in the cell cycle regulations
  • genomic instabilities (mutations to DNA repair genes)

Genetics (6 decks)

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