Lecture 5

Question 1

What are the 3 centromere locations?

Answer 1

Metacentric: middle
Acrocentric: towards one end
Telocentric: at one end

Question 2

Human chromosomes are what in terms of centromere location?

Answer 2

Metacentric and acrocentric

Question 3

What are the steps to view metaphase chromosomes from white blood cells?

Answer 3

1) isolate blood (want WBC)
2) wait for WBC to grow (with WBC growth factor)
3) halt cell cycle in metaphase using a microtubule inhibitor
4) drop WBCs onto a slide (WBCs burst)
5) add Giemsa stain = metaphase spread
6) take photo and arrange chromosomes into standard pattern = karyogram
7) describe results in a statement = karyotype

Question 4

Chromosomes have a p arm and q arm. What are these?

Answer 4

p arm (petite = small)

q arm (queue = tail)

Question 5

What is a chromosome band?

Answer 5

stained segment of condensed chromosome visible under a microscope, such as made by a giemsa stain

Question 6

Describe dark chromosome bands

Answer 6

Dark bands (G+) are A-T rich, gene poor, and heterochromatin (more tightly packed)

Question 7

Describe light chromosome bands

Answer 7

Light bands (G-) are G-C rich, gene-rich, euchromatin (loosely packed, transcriptionally active)

Question 8

What colour is a giemsa dark band? light band?

Answer 8

purple

pink

Question 9

Are chromosome bands named in order?

Answer 9

No. Better prep shows more bands, therefore, it is not a good enough system

Question 10

What is the actual system for naming chromosome sections?

Answer 10

using regions

numbered from centromere to each end

i.e. p arm region 1, q arm region 1, q arm region 2

Question 11

Regions contain bands. Bands contain sub-bands, named by decimal points. How do you say 18p11.2?

Answer 11

chromosome 18, p arm, region 1, band 1, sub-band 2

Question 12

How do you write chromosome map locations?

Answer 12

chromosome number, arm (p/q), region, band, sub-band

Question 13

If chromosome number changes, how do you describe autosomes and sex chromosomes?

Answer 13

autosomes: + extra, - missing

sex chromosomes: list them

Question 14

What are the possible chromosome structure changes? How do you write them in chromosome maps?

Answer 14

del: deletion
dup: duplication
inv: inversion
t: translocation

Question 15

How do you pronounce 12p12?

Answer 15

(chromosome) 12, p arm, region 1, band 2