Lab 4 (chromosomes)

Question 1

Polytene chromosomes

Answer 1

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

Question 2

How do Polytene chromosomes form?

Answer 2

Endomitosis

Question 3

Endomitosis

Answer 3

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

Question 4

Dark bands vs light bands

Answer 4

Dark bands = transcriptionally INACTIVE

Light bands = transcriptionally ACTIVE

Question 5

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

Answer 5

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.

Question 6

1q12

Answer 6

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

Question 7

aneuploid

Answer 7

one or more INDIVIDUAL chromosomes are added or deleted

Question 8

Polyploid

Answer 8

one or more complete SETS of chromosomes are added

Question 9

abbreviations:
Deletion
Inversion 
Duplication
Translocation

Answer 9

del
Inv
dup
t

Question 10

Pericentric Inversion

Answer 10

Includes the centromere. (peri = around)

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

Question 11

Paracentric inversion

Answer 11

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)

Question 12

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

Answer 12

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

Paracentric inversion

Question 13

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

Answer 13

46, XY, dup (3) (q13)

Question 14

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

Answer 14

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

Pericentric inversion

Question 15

Description symbol for: A female with Patau syndrome.

Answer 15

47, XX, +13

Question 16

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._

Answer 16

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

Question 17

Step 1 to prepare Karyotype

Answer 17

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)

Question 18

Step 2 to prepare Karyotype

Answer 18

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.

Question 19

Step 3 to prepare Karyotype

Answer 19

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

Question 20

Step 4 to prepare Karyotype

Answer 20

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

Question 21

Step 5 to prepare Karyotype

Answer 21

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

Question 22

Step 6 to prepare Karyotype

Answer 22

6) Photograph the spread

Question 23

Step 7 to prepare Karyotype

Answer 23

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

Question 24

one or more INDIVIDUAL chromosomes are added or deleted

Answer 24

Aneuploid