A chart that
shows the size,
shape and
arrangement of
chromosomes.
What do you notice about these karyotypes?
A normal male karyotype. Notice that the 23rd pair doesn’t appear to match.
In humans, the last set of chromosomes determines whether a person will be male
or female. If a person received a normal “X’s” from each parent they are female. If
they received an “X” from mom and a “Y” from dad, however, then they are male.
Women can only donate X’s. Men can donate X or Y.
A normal female karyotype. Notice that all of the chromosomes match their partners;
there are no mistakes or alterations. Each chromosome has exactly one partner, for a
total of 46.
• Two chromosomes for each number
• The 23rd set doesn’t match
• Except for the 23rd set, the chromosomes
get smaller and smaller
• The chromosome contain dark bands
• All of the sets are numbered except for 23
• There are 46 total chromosomes
What else do you
observe on this
chromosome?
All human chromosomes have 2 arms -- a short arm and a long arm -- that
are separated from each other only by the centromere, the point at which
the chromosome is attached to the spindle during cell division. The short
arm is termed the "p arm" while the long arm of the chromosome is termed
the "q arm."
The symbol "p" was chosen to designate the short arm because "p" stands
for "petit", "small" in French. The letter "q" was selected to signify the long
arm merely because "q" is the next letter in the alphabet.
What are chromosome abnormalities?
There are many types of chromosome
abnormalities. However, they can be organized
into two basic groups:
1. Numerical Abnormalities
2. Structural Abnormalities
Numerical Abnormalities:
1. Monosomy- when an individual is
missing a chromosome from a pair
2. Trisomy- has more than two
chromosomes of a pair
Turner Syndrome is an
example of monosomy,
where the individual - in
this case a female - is
born with only one sex
chromosome, an X.
An example of a
condition caused by
numerical
abnormalities is
Down Syndrome,
also known as
Trisomy 21 (an
individual with
Down Syndrome has
three copies of
chromosome 21,
rather than two).
Structural Abnormalities:
When the chromosome's structure is altered. This can take
several forms:
Translocations: When a portion of one
chromosome is transferred to another
chromosome. There are two main types of
translocations. In a reciprocal translocation,
segments from two different chromosomes have
been exchanged. In a Robertsonian translocation,
an entire chromosome has attached to another at
the centromere.
Robertsonian translocation
Inversions: A portion of the chromosome
has broken off, turned upside down and
reattached, therefore the genetic material
is inverted.
Deletions: A portion of the chromosome is
missing or deleted.
Duplications: A portion of the
chromosome is duplicated, resulting in
extra genetic material.
1.Deletion
2.Duplication
3.Inversion