Download Changes in Chromosome Number

12-4 Changes in Chromosome Number
Karyotype
-
A picture of a person's chromosomes, arranged by size
and grouped into homologous pairs.
Tests to Examine
Chromosomes
Amniocentesis a needle is used
to withdraw fluid
from the uterus
which contains
fetal cells
Chorionic Villi
Sampling - a
suction tube
inserted into the
vagina removes
fetal cells
*Tests are not
usually performed
due to risk of
spontaneous
abortion.
Occasionally, errors occur during cell division that result in the offspring receiving too
many or too few chromosomes (euploidy)
Polyploidy - three or more complete sets of chromosomes. common in plants
Aneuploidy - when an organism has more or less than the normal (monosomy / trisomy)
Down's Syndrome ( Trisomy #21)
- mental retardation
- short stature, round face
- more likely in women over 40
- retardation is now known to be caused the the GART gene
Other Syndromes - Turner (XO), Klinefelter (XXY), Edward (Trisomy 13), Supermale
(XYY), Poly-X Females (XXX)
12.4 - Changes in Chromosome Structure
Chromosome Mutations
Inversion (B)
Deletion (A)
Duplication (D)
Translocation (C)
Williams Syndrome - deletion on chromosome 7
Cri du Chat Syndrome - deletion on chromosome 5