Classifying Chromosomes

Question 1

what 3 features classify chromosomes?

Answer 1

size, centromere position, banding pattern

Question 2

what are the variations on centromere position

Answer 2

telocentic, acrocentric, submetacentric, metacentric

Question 3

metacentric

Answer 3

the centromere is near the center of the chromosome. 1,3,19,20

Question 4

submetacentric

Answer 4

one chromosome arm is longer han the other. short arm=p. 2,4-12,16-18,X

Question 5

acrocentric

Answer 5

centromere is very near to one end. 13-15, 21,22,Y

Question 6

telocentric

Answer 6

centromere is at the very end of the chromosome. NOT IN HUMANS

Question 7

different banding patterns are based on?

Answer 7

type of dye used to paint the chromosomes, treatment used to prepare the chromosomes

Question 8

list the 3 steps to band chromosomes

Answer 8

~ cells to be analysed are cultured
~ cells are stopped in metaphase
~cells are spread on a slide, fixed, and colored

Question 9

what cells are used for karyotyping

Answer 9

fibroblasts, bone marrow, solid tumors, immortalized cell lines

Question 10

a Band

Answer 10

is part of a chromosome that is easily distinguishable from its adjacent segment by appearing darker or brighter

Question 11

numbering of bands originates from

Answer 11

the centromere outwards

Question 12

what are the 4 methods for staining

Answer 12

~G banding
~Q banding
~R banding
~C banding

Question 13

G banding

Answer 13

is a system of dark and light bands, uses trypsin and Giesma.
light bands are euchromatin, early replicating, GC rich, contain many genes

Question 14

Q banding

Answer 14

is a system of bright and dull bands, uses a Quinacrine Mustard , has a high affinity for AT rich regions (bright bands)

Question 15

R banding

Answer 15

denatures the chromosomes in a saline solution and then uses Giesma. Results in dark/light banding but now euchromatin (GC rich) is dull

Question 16

C banding

Answer 16

use of giesma preceeded by denaturation using barium oxide . Leaves heterochromatic regions dark (especially centromere)

Question 17

ideogram

Answer 17

is a schematic representation of a single chromosome

Question 18

Molecular cytogenetics uses what 2 techniques?

Answer 18

FISH, and CGH

Question 19

What is the basic FISH procedure?

Answer 19

~get a labelled probe
~denature the probe
~prepare the chromosomes on a slide
~denature them
~combine the 2
~incubate in an oven for 16-72 hours

Question 20

Polymorphisms are?

Answer 20

stable, present in all cells of a person, inherited in a mendelian fashion

Question 21

most common polymorphisms are?

Answer 21

~centromeres of 1,9,16
~Satellites of acroentric chromosomes
~distal end of Y chromosomes

Question 22

fragile site

Answer 22

is a heritable locus on chromosomes that forms a gap/constriction along the chromosome. They tend to break during karyotype prep, replication

Question 23

FRAXA

Answer 23

associated with fragile X syndrome, cause of hereditary mental retardation, is a rare fragile site