18 - Cytogenetic Techniques and Chromosome Function

Question 1

Roles of chromosomes

Answer 1

• Transmit genetic information (mitosis and meiosis)
• Express genetic information (protein and non-coding RNA)

Question 2

C

Answer 2

Amount of DNA

Question 3

n

Answer 3

Number of Chromosomes

Question 4

ploidy

Answer 4

• Number of copies of chromosomes. Varies with cell type

Question 5

Haploid

Answer 5

Gametes (n chromosomes, C DNA) n=23

Question 6

Diploid

Answer 6

Most human and mammalian cells (2n chromosomes, 2C DNA) n=46

Question 7

Polyploid

Answer 7

non-mammalian cells (4n, 8n, etc)

Question 8

Karyotype

Answer 8

Species specific chromosome number, size and shape at metaphase

Question 9

3 elements required for a chromosome to be copied

Answer 9

• A centromere (narrowest part of chromosome, where spindle fibres attach)
• Replication origins (initiation)
• Telomeres (ends of linear chromosomes)

Question 10

What does meiosis produce

Answer 10

haploid cells. Haploid sperm (23) + haploid egg (23) = diploid zygote (46)

Question 11

What does mitosis produce

Answer 11

diploid cell (2n) producing diploid cell (2n)

Question 12

Tightly packed DNA

Answer 12

No gene expression, can be seen under light microscope

Question 13

Cytogenetics

Answer 13

Study of how chromosomes relate to cell behaviour

Question 14

Preparation of sample for cytogenetic analysis

Answer 14

• Blood sample taken, isolate white blood cells
• Culture cells in medium
• Stimulate to divide with mitogen
• treat with spindle disrupting agent (can enter metaphase but not progress)

Question 15

What are chromosome numbers 1-22 based on

Answer 15

Size

Question 16

Metacentric

Answer 16

Centromere close to middle of chromosome

Question 17

Submetacentric

Answer 17

Centromere in between middle of chromosome and telomeres

Question 18

Acrocentric

Answer 18

Centromere close to telomere

Question 19

p arm

Answer 19

Short arm (petite)

Question 20

q arm

Answer 20

Long arm

Question 21

G banding

Answer 21

• Chromosomes treated with trypsin and stained with Giemsa
• Preferentially binds AT rich regions
• Produces alternating dark and light bands
• Genes are associated with GC rich sequences
• Dark bands are gene poor, light bands are gene rich

Question 22

Q banding

Answer 22

Chromosomes stained with fluorescent dye, binds to AT rich DNA

Question 23

R banding

Answer 23

Reverse of G banding. Heat denatures AT rich DNA, GC specific dyes

Question 24

T banding

Answer 24

Identifies subset of R bands concentrated close to telomeres

Question 25

C banding

Answer 25

Constitutive heterochromatin, mainly at centromeres

Question 26

How can resolution be increased

Answer 26

By using more elongated chromosomes (prometaphase)

Question 27

Proximal

Answer 27

Close to centromere

Question 28

Distal

Answer 28

more distant from centromere

Question 29

Karyogram

Answer 29

Graphical representation of individuals full set of chromosomes

Question 30

FISH fluorescence labelling

Answer 30

• Fluorophore (fluorescent dye) is bound to the probe
• Fluorophore is associated with target sequence

Question 31

Interphase FISH

Answer 31

Interphase chromosomes are much less condensed than in metaphase. Detects translocations