Lab 4 (chromosomes) Flashcards

1
Q

Polytene chromosomes

A

It is not a single chromosome, but thousands of aligned copies of a chromosome that are stacked up in a bundle.

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2
Q

How do Polytene chromosomes form?

A

Endomitosis

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3
Q

Endomitosis

A

Multiple rounds of chromosomal replication without separation of the sister chromatids or cytokinesis.

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4
Q

Dark bands vs light bands

A

Dark bands = transcriptionally INACTIVE

Light bands = transcriptionally ACTIVE

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5
Q

Describe the size of human chromosomes to the fly polytene chromosomes.

A

Polytene chromosomes are larger than human chromosomes. The diameter of the nucleus of the salivary gland cells of larva is 2 times bigger than the nucleus of human cells.

The polytene chromosomes appear to contain five long and one short arm radiating from a central point called chromocentre. It is formed by the fusion of centromeres of all the eight chromosomes found in the cell.

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6
Q

1q12

A

Chromosome 1
q = long arm
1 = region
2 = band

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7
Q

aneuploid

A

one or more INDIVIDUAL chromosomes are added or deleted

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8
Q

Polyploid

A

one or more complete SETS of chromosomes are added

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9
Q
abbreviations:
Deletion
Inversion 
Duplication
Translocation
A

del
Inv
dup
t

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10
Q

Pericentric Inversion

A

Includes the centromere. (peri = around)

one inversion is in the p (small) arm and the other is in the q (long) arm.

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11
Q

Paracentric inversion

A

It does NOT include the centromere. (para = next to)

And both breaks occur in one arm of the chromosome either p(small) or q(long)

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12
Q

Description symbol for: a male with an inversion on chromosome 10, with one breakpoint located in region 1, band 1 of the long arm, and the other breakpoint in region 2, band 1 of the long arm.

Type of inversion

A

46, XY, inv (10) (q11 q21)

Paracentric inversion

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13
Q

Description symbol for: A male with a small duplication located on the long arm of chromosome 3 within region 1, band 3.

A

46, XY, dup (3) (q13)

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14
Q

Description symbol for: A male with an inversion on chromosome 5, with one breakpoint located in region 1, band 4 of the short arm, and the other breakpoint in region 2, band 1 of the long arm.

Type of inversion

A

46, XY, inv (5) (p14 q21)

Pericentric inversion

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15
Q

Description symbol for: A female with Patau syndrome.

A

47, XX, +13

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16
Q

Description symbol for: A male with a reciprocal translocation involving chromosomes 2 and 6. The breakpoint on chromosome 2 is on the short arm, region 1, band 3. The breakpoint on chromosome 6 is on the long arm within region 2, band 2._

A

46, XY, t(2; 6), (p13; q22)

17
Q

Step 1 to prepare Karyotype

A

1) A sample of blood is drawn WBC. Fetus –> amniocentesis or Chorionic Villus Sampling ( sampling of the chorionic villus (placental tissue) and testing it for chromosomal abnormalities)

18
Q

Step 2 to prepare Karyotype

A

2) Culture cells and add COLCEMID (related to colchicine a drug that Treats and prevents gout attacks, gouty arthritis)
COLCEMID disrupts mitotic spindles and prevents completion of mitosis.

19
Q

Step 3 to prepare Karyotype

A

3) Suspend cells in hypotonic solution. This causes the nuclei to swell to facilitate the spreading of chromosomes.

20
Q

Step 4 to prepare Karyotype

A

4) the swollen cells are fixed, dropped into a slide and dried

21
Q

Step 5 to prepare Karyotype

A

5) Stain the chromosomes to differentiate between dark and light bands

22
Q

Step 6 to prepare Karyotype

A

6) Photograph the spread

23
Q

Step 7 to prepare Karyotype

A

7) Cut them out and organize them in the standard way.

24
Q

one or more INDIVIDUAL chromosomes are added or deleted

A

Aneuploid