Cytogenetics

Question 1

The study of whole sets of chromosomes.

Answer 1

Karyology

Question 2

Show lesser differences between smaller and larger chromosomes in a set.
Has more:
Metaphase chromosomes
No advanced features

Answer 2

Symmetric Karyotype

Question 3

Show larger differences between smaller and larger chromosomes in a set.
Has more:
Acrocentric chromosomes
Relatively advanced features

Answer 3

Asymmetric Karyotype

Question 4

1, 3, 16, 19, 20

Answer 4

Metacentric

Question 5

2, 4, 5, 6, 7, 8, 9, 10, 11, 12, 17, X

Answer 5

Submetacentric

Question 6

13, 14, 15, 18, 21, 22, Y

Answer 6

Acrocentric

Question 7

A Russian scientist
Suggested that in flowering plants, there is a predominant trend toward karyotype asymmetry

Answer 7

G.A Levisky

Question 8

Dark-stained (tightly-packed)

Answer 8

Heterochromatin

Question 9

Light-stained (loosely-packed)

Answer 9

Euchromatin

Question 10

Methyaltion

Answer 10

Tightly Packed (Heterochromatin).

Question 11

Histone Acetylation

Answer 11

Loose Packing (Euchromatin)

Question 12

Glacial acetic acid with methanol proportion

Answer 12

1:3

Question 13

Glacial acetic acid with methanol
Which is Fixative ?

Answer 13

Methanol

Question 14

What top tube used for karyotyping ?

Answer 14

Green top

Question 15

Hypotonic Solution

Answer 15

Potassium chloride (alternative: sodium citrate)

Question 16

Culture medium
Allows lymphocytes to grow/proliferate.

Answer 16

RPMI with Fetal Bovine Serum

Question 17

Induces mitosis; kickstart to mitosis.
Removes RBCs

Answer 17

Phytohemagglutinin

Question 18

Arrest mitosis at metaphase stage.

Answer 18

Colcemid/colchicine

Question 19

Stain for karyotyping

Answer 19

Giemsa Stain

Question 20

Used to digest chromosomes so they stain better.
Improves activity of the stain

Answer 20

Trypsin

Question 21

Antibiotics to prevent contamination.

Answer 21

Penicillin + streptomycin

Question 22

What blood is used in Karyotyping ?

Answer 22

Venous Blood

Question 23

Culture medium

Answer 23

RPMI, FBS, with antibiotics

Question 24

Step 1 for Karyotyping

Answer 24

• The collected blood will be grown in vitro by adding cell culture growth medium, fetal bovine serum, antibiotics, and phytohemagglutinin (PHA) – the reagent that induces mitotic activity.
• The cultured blood cells will be grown at 37°C (body temperature) incubator for 3 days

Question 25

Step 2 for Karyotyping

Answer 25

**Addition of pre-warmed colcemid (also known as colchicine)**, the reagent that arrests the cell cycle at the metaphase stage, into the culture and **incubate for 15 mins** Centrifuge the tube at **1000 RPM for 10 mins** and the cell pellet was resuspended in warm hypotonic solution (can be KCl or sodium citrate) and the solution was mixed. **Incubate at room temperature for 15 mins.**

Question 26

Step 3 for Karyotyping

Answer 26

**Fixing the Cells** The cell **suspension in hypotonic state** will be **centrifuged at 1200 RPM for 5 mins.** The cell pellet will be treated with a **fixative solution (absolute methanol:glacial acetic acid [3:1]) or Carnoy’s fixative and will be centrifuged at 1200 RPM for 5 mins.** The process will be **repeated 3x and the final addition of fixative solution will require incubation at 4°C for 10 mins.**

Question 27

Step 4 for Karyotyping

Answer 27

**Making the Chromosome Slides** 5 or 6 cold slides will be layered next to each other in a paper towel. **2 or 3 drops of the samples will be dropped onto each slide and dry spontaneously.** The slide will be **stained by GTG-banding (G-bands by Trypsin using Giemsa),** the most common method of

Question 28

Step 5 for Karyotyping

Answer 28

**Slide Analysis** Slides that will be chosen for analysis and visualization must be: **Properly-trypsinized chromosomes Clearly-defined metaphase spreading **

Question 29

GC-rich region

Answer 29

Euchromatin

Question 30

AT-rich region

Answer 30

Heterochromatin

Question 31

What are always used for chromosome banding studies

Answer 31

Metaphase chromosomes

Question 32

Giemsa stain AT-rich regions stain darker than GC-rich regions Hetero: dark Eu: Light

Answer 32

G-banding

Question 33

Quinacrine fluorescent dye stains AT-rich regions Hetero: Dark Eu: Light

Answer 33

Q-banding

Question 34

Opposite to G-banding Hetero: Light Eu: Dark

Answer 34

R-banding

Question 35

Stains heterochromatic regions close to the centromeres using a strong alkali. Barium hydroxide Denatures the AT-rich regions. Hetero: dark Eu: Light Usually stains the entire long arm of the Y chromosome

Answer 35

C-banding

Question 36

* Chromosome * Stained with quinacrine mustard * Subjected to UV light * Banding pattern * Used when G-band is not accepted. * Used in the study of chromosome heteromorphism.

Answer 36

Q-banding

Question 37

Superior banding pattern for plants.

Answer 37

N-banding

Question 38

* Used in the identification of bands rich in sulfur content. * Used in the identification of chromosomal abnormalities. * Gene Mapping * Treated with Giemsa * Not used in plants.

Answer 38

G-Banding

Question 39

* Identification of chromosomes particularly in insects and plants. * Identification of bivalents at diakinesis using both centromere positions. * Paternity testing * Gene Mapping

Answer 39

C-Banding