Skip to content
National Cancer Institute
at the National Institutes of Health
Send to Printer
NCI Dictionary of Genetics Terms
Starts with
Contains
#
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
All
trisomy
(TRY-soh-mee)
The presence of an extra chromosome, resulting in a total of three copies of that chromosome instead of the normal 2 copies (e.g., trisomy 21, or Down syndrome).
