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MOLECULAR BIOLOGY > PREFI LEC: CHROMOSOMAL STRUCTURE & CHROMOSOMAL MUTATIONS > Flashcards

PREFI LEC: CHROMOSOMAL STRUCTURE & CHROMOSOMAL MUTATIONS Flashcards

1
Q

All of the genes found in a single individual

A

HUMAN GENOME

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2
Q

_______ nucleotide base pairs of DNA organized in _____

A

2.9 billion; 23 chromosomes

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3
Q

Diploid organisms

A

46 chromosomes

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4
Q

Each chromosome is a double helix of
______

A

DNA

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5
Q

largest chromosome

A

Chromosome 1

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6
Q

smallest chromosome

A

Chromosome 21

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7
Q

A difference in DNA sequence found in 1%-2% or more of a given population

A

POLYMORPHISM

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8
Q

Examples: blood types in humans, color of hair & eyes, separation of most higher organisms into male & female sexes, polymorphisms used for human ID & paternity testing

A

POLYMORPHISM

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9
Q

A change in the order/sequence of nucleotide in DNA found in <1%2% of a given population (due to errors in DNA replication, exposure to mutagens, or other factors)

A

MUTATION

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10
Q

Maintained a population through a balance of positive & negative phenotype

A

BALANCED POLYMORPHISM

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11
Q

Abnormal RBCs resulting into resistance to infection by Plasmodium species (malaria)

A

Sickle cell anemia

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12
Q

Does not have any detectable negative effects on an organism’s health/fitness

A

BENIGN POLYMORPHISM

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13
Q

Typically common in populations, do not lead to disease/other adverse phenotypic outcomes

A

BENIGN POLYMORPHISM

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14
Q

Examples: blood type (ABO blood group), eye color, facial features, skin pigmentation

A

BENIGN POLYMORPHISM

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15
Q

Affect single genes & are often, but
not always, small changes in the DNA sequence

A

Gene Mutations

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16
Q

Affect the structures of entire chromosomes

A

Chromosome Mutations

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17
Q

Changes in the number of
chromosomes (aneuploidy)

A

Genome Mutations

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18
Q

Process by which the long, linear DNA molecules of eukaryotic chromosomes are organized & packaged into highly condensed structures

A

CHROMOSOMAL COMPACTION

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19
Q

IMPORTANT:
1. Chromosome behavior is dependent on chromosome structure & DNA sequences (position effect)
2. Chromosome topology affects gene activity (highly compacted DNA = less available for RNA transcription)

A

CHROMOSOMAL COMPACTION

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20
Q

Group A

A

1, 2 (large metacentric)
3 (Large submetacentric)

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21
Q

Group B

A

4, 5 (Large submetacentric)

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22
Q

Group C

A

6-12, X (Medium-sized submetacentric)

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23
Q

Group D

A

13-15 (Medium-sized acrocentric with satellite)

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24
Q

Group E

A

16 (Short Metacentric)
17, 18 (Short Submetacentric)

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25
Q

Goup F

A

19, 20 (Short Metacentric)

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26
Q

Group G

A

21, 22 (Short acrocentric with satellite)
Y (Short acrocentric)

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27
Q

TASM

A

TELOCENTRIC TO ACROCENTRIC TO SUBMETACENTRIC TO METACENTRIC

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28
Q

7 TYPES OF VISUALIZING CHROMOSOMES

A

Conventional cytological stains
Fluorescent dyes
Chemical dye
Harsher treatment of chromosomes
Alkali treatment
Nucleolar organizing region (NOR) staining
4’6-diamidino-2phenylindole (DAPI)

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29
Q

Feulgen, Wright, & hematoxylin

A

Conventional cytological stains

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30
Q

▪ Quinacrine & quinacrine mustard
▪ Pattern: Q bands – 1st demonstrated by Caspersson, Zech, & Johansson (1970)

A

Fluorescent dyes

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31
Q

▪ Giemsa stain
▪ Pattern: G bands

A

Chemical dye

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32
Q

▪ Pattern: R bands (can be visualized after staining w/ acridine orange)

A

Harsher treatment of chromosomes (87ºC for 10 min, then cooling to 70ºC) before Giemsa staining)

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33
Q

▪ Centromere staining
▪ Pattern: C bands

A

Alkali treatment

34
Q

Silver nitrate: stain specifically at the constricted regions, or stalks, on the acrocentric chromosomes

A

Nucleolar organizing region (NOR) staining

35
Q

▪ Binds to the surface grooves of dsDNA Fluoresces blue under UV light (353-nm wavelength)
▪ Visualization of chromosomes & whole nuclei

A

4’6-diamidino-2phenylindole (DAPI)

36
Q

Chromosome banding facilitates the:

A

▪ Detection of deletions, insertions, inversions, & other abnormalities
▪ ID of distinct chromosomal locations

37
Q

▪ Indirect method of detecting genome mutations, or aneuploidy
▪ Measuring DNA content of individual cells
▪ Aneuploidy is reflected by a change in the amount of DNA

A

FLOW CYTOMETRY

38
Q

Direct method of detecting genome mutations, or aneuploidy 🡪 observation of metaphase chromosome structure by arranging them according to size

A

KARYOTYPING

39
Q

chart that shows the complete set of chromosome in a cell

A

Karyotype

40
Q

Performed in light microscope

A

KARYOTYPING

41
Q

Exchange of genetic material between chromosomes

A

Translocation

42
Q

2 TYPES OF Translocation

A

Reciprocal
Robertsonian

43
Q

Parts of 2 chromosomes exchange

A

Reciprocal

44
Q

Movement of long arm of an acrocentric chromosome to the centromere of another acrocentric chromosome

A

Robertsonian

45
Q

Loss of chromosomal material

A

Deletion

46
Q

Gain of chromosomal material

A

Insertion

47
Q

Result from excision, flipping, & reconnecting chromosomal material w/in the same chromosome

A

Inversions

48
Q

include centromere in the inverted region

A

Pericentric

49
Q

involve sequences within 1 arm of the chromosome

A

Paracentric

50
Q

Metacentric chromosome resulting from transverse splitting of centromere during cell division

A

Isochromosome

51
Q

Results from deletion of genetic regions from ends of the chromosome and a joining of the ends to form a ring

A

Ring chromosome

52
Q

Translocated / otherwise rearranged
parts from 2 or more unidentified chromosomes joined to a normal chromosome

A

Derivative chromosome

53
Q

that the 1st chromosome mutations associated with human disease were visualized in the _____ in leukemia cells

A

1960s

54
Q

_______ observed an abnormally small chromosome 22 in leukemia cells (Philadelphia chromosome)

A

Peter Nowell and David Hungerford

55
Q

1st described the translocation between chromosomes 8 & 21 in patients with acute myeloblastic leukemia

A

1972: Janet Rowley

56
Q

▪ Method widely used to detect proteins & nucleic acids
▪ Targets specific sequences of chromosomes w/ fluorescent probes 🡪 designed to hybridize to critical areas that are amplified/deleted/translocated/ otherwise rearranged in disease states

A

FLUORESCENCE IN SITU HYBRIDIZATION (FISH)

57
Q

Requires fluorescence microscope & special filters

A

FLUORESCENCE IN SITU HYBRIDIZATION (FISH)

58
Q

2 TYPES OF FLUORESCENCE IN SITU HYBRIDIZATION (FISH)

A

interphase FISH & metaphase FISH

59
Q

▪ Used to study the genetic content & organization of non-dividing cells, particularly cells in the interphase stage of the cell cycle
▪ Bound probe is visualized under a fluorescent microscope as a point of fluorescent light in the nucleus of the cell

A

Interphase FISH

60
Q

______= 1 signal

A

Deletion

61
Q

_____= more than 2 signals

A

Duplication

62
Q

Commonly used to study prenatal samples, tumors, & hematological malignancies

A

Interphase FISH

63
Q

bind to regions spanning the breakpoint of translocations

A

Dual-color probes/dual-fusion probes

64
Q

bind to the intact chromosome flanking the translocation breakpoint

A

Break-apart probes

65
Q

▪ Hybridize to highly repetitive alpha satellite sequences surrounding centromeres
▪ Detect aneusomy of any chromosome ▪ + region-specific probes = to confirm deletions / amplifications in specific chromosomes
▪ + dual-color probes = tricolor probe serves as a control for amplification/loss of 1 of the chromosomes involved in the translocation
▪ Example: IGH/MYC/CEP 8 Tri-color probes

A

Centromeric (CEN) probe

66
Q

▪ Designed to specifically target & visualize the telomeric regions of chromosomes
▪ Useful for detection of chromosome structural abnormalities (cryptic translocations/sub-telomeric deletions) that are not easily visualized by standard karyotyping

A

Telomeric probes

67
Q

Preparation of sample

A

▪ Permeabilize the cells for optimal-target interaction & to maintain cell morphology
▪ Fresh interphase cells are incubated overnight (aging) after deposition on slides
▪ Cells are treated with protease and fixed with 1% formaldehyde
▪ Cells are dehydrated in graded concentration of ethanol
▪ Denaturation

68
Q

Under a fluorescent microscope w/ appropriate color-distinction filters: signal should be bright, specific to the target in the cell nuclei, & free of high background noise

A

Quality of the probe

69
Q

▪ 1-10 µg of probe may be used in a hybridization volume of 3-10µL
▪ Hybridization: 37ºC-42ºC in a humidified chamber
▪ Slides are cover-slipped & sealed

A

Both probe & target must be denatured prior to hybridization

70
Q

Rinsing off of the unbound probe

A

Washing

71
Q

▪ Sample is observed under fluorescent microscope
▪ Probe signals should be visible from entire intact nuclei
▪ Adequate number of cells must be visible

A

Microscopic analysis

72
Q

▪ Allows analysis of small regions not visible by regular chromosome banding
▪ Probes that cover the entire chromosome/whole chromosome paints
▪ Combination of 5 fluors & using a special imaging software 🡪 spectral karyotyping can distinguish all 23 chromosomes by chromosome-specific colors (detect abnormalities that affect multiple chromosomes)
▪ Telomeric & centromeric probes are also used 🡪 detection of aneuploidy & other genomic mutations

A

Metaphase FISH

73
Q

PROCEDURE OF Metaphase FISH

A

▪ Culture of cells for 72 hours ▪ 45 mins before harvesting, colcemid is added
▪ Cells are suspended in a hypotonic medium (0.075 M KCl) & fixed with methanol/acetic acid (3:1)
▪ Fixed cell suspension is applied to an inclined slide & allowed to dry
▪ 2nd treatment w/ 70% acetic acid ▪ Under a phase contrast microscope 🡪 chromosome should appear well separated w/ sharp borders & cytoplasm should not be visible
▪ Dry the slide & proceed to hybridization

74
Q

▪ Simultaneous use of combinations of different locus-specific probes & chromosome paints
▪ Uses multiple fluorescently labeled probes that target different chromosomal regions/genes
▪ Identifies specific chromosomal regions based on the presence/absence of the probe color visualized with specific filters
▪ May show cryptic translocations & insertions

A

MULTICOLOR FISH (QMFISH or MFISH)

75
Q

▪ Detection of intrachromosomal amplifications/deletions
▪ Test DNA is isolated & labeled along with a reference DNA

A

COMPARATIVE GENOME HYBRIDIZATION (CGH)

76
Q

fluoresces @ 550 nm “green” (reference DNA)

A

Cy3

77
Q

fluoresces @ 650-667 nm “red” (test DNA)

A

Cy5

78
Q

fluoresces in the red-orange region

A

Cy3.5

79
Q

can result in cells w/ too few or too many copies of a chromosome

A

Error in cell division

80
Q

chromosomal errors can appear in eggs as women age

A

Maternal age

81
Q

conclusive evidence is currently lacking

A

Environmental conditions

MOLECULAR BIOLOGY (9 decks)

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