3. The breakdown of a Chromosome
Each autosome is numbered from 1-22,
sex chromosomes either X or Y
p arm
(short arm)
q arm
(long arm)
Centromere
4. Chromosome Labeling
Example - 1q2.4
The first chromosome, long arm, second
region of the chromosome, the fourth band of
that sub-region
Chromosome is
identified with
a number
ranging 1-22,
or X and Y
Each arm
divided into
sub-regions
and identified
by a number
Each sub-
region divided
into bands
identified with
a number
5. A Karyotype
Definition
A photographic
arrangement of
a complete set
of chromosomes
of a cell or
organism
1 2 3 4 5
6 7 8 9 10 11 12
13 14 15 16 17 18
19 20 21 22 X Y
6. Obtaining a Sample
Fetal samples for karyotypes are commonly
obtained in two ways
1.Amniocentesis – sample taken from the
fluid of the amniotic sac
2.Chorionic Villus Sampling – sample
taken from the fetal tissue that forms
part of the placenta
7. Obtaining a Karyotype
Chromosomes are stained for easy
visualization
Light microscope used to view chromosomes
in metaphase of mitosis
Chromosomes arranged into homologous
pairs based on size and banding patterns
8. Staining
Banding patterns can be visually identified on
chromosomes after staining.
Traditional Types
G-Banding – Giemsa stain
Q-Banding – Fluorescent stain
R-Banding – Reverse Giemsa stain
New Type
Fluorescence In Situ Hybridization techniques
9. Importance of Karyotypes
Karyotypes show the chromosomal
makeup of an individual. Knowing the
number of chromosomes is essential for
identifying chromosomal variations that
cause genetic disorders.
10. References
1. Fairbanks, D. J., Anderson, W. R. Genetics: The Continuity
of Life. Pacific Grove, CA: Brooks/Cole Publishing
Company; 1999.
2. NIH. Amniocentesis [online]. 2004. [cited 2004 Feb 6].
Available from URL:
http://www.nlm.nih.gov/medlineplus/ency/article/00392
1.htm.
3. NIH. Chorionic villus sampling [online]. 2004. [cited 2004
Feb 6]. Available from URL: http://www.nlm.nih.gov/
medlineplus/ency/article/003406.htm.
4. Campbell, N. A. Biology. 3rd ed. Redwood City, CA: The
Benjamin/Cummings Publishing Company, Inc.; 1993.
11. References (continued)
5. On-line medical dictionary. G-banding: Banding pattern.
1997. [cited 2004 Feb 6]. Available from URL:
http://cancerweb.ncl.ac.uk/cgi-bin/omd?G-banding.
6. On-line medical dictionary. Q-banding. 2000. [cited 2004
Feb 6]. Available from URL:
http://cancerweb.ncl.ac.uk/cgi-bin/omd?query=q-
banding.
7. On-line medical dictionary. R-banding stain. 2000. [cited
2004 Feb 6]. Available from URL:
http://cancerweb.ncl.ac.uk/cgi-bin/omd?R-
banding+stain.
8. National Human Genome Research Institute, Fluorescence
In Situ Hybridization (FISH). 2004 [cited 2004 Feb 6].
Available from URL: http://www.genome.gov/10000206.
