Background
DNA is duplicated and packaged into chromosomes prior to the onset of mitosis. Each double-
stranded DNA molecule is wrapped around a group of proteins (histones) to form what looks like
beads on a string. This structure is then folded and coiled several times to form one half of the
resulting chromosome (a chromatid). Each chromosome consists of two chromatids (sister
chromatids) that are joined at a region called a centromere. Consult the text for chromosome
images.
Non-histone proteins play a very important role in holding the chromosome structure together.
These proteins can be treated with enzymes and stained which produces a series of light and dark
bands along the length of the chromosome. The resulting banding patterns are unique to each
chromosome pair (remember that we are diploid individuals which means we get 23
chromosomes form our mothers and 23 from our fathers) and allows for the identification of
each chromosome. The human chromosomes in the image below have been stained and arranged
into a karyotype. A karyotype of human chromosomes is shown on pg 205 in the text.
Objective
Your objective is to identify chromosomes based upon their banding patterns and to identify
some chromosomal abnormalities that occur in humans.
Procedure
Go to the University of Arizona Human Biology Human Karyotype web page
( complete
the activity, and answer the following questions.
1. What notation would you use to characterize Patient A’s karyotype?
2. What diagnosis would you give patient A?
3. What notation would you use to characterize Patient B’s karyotype?
4. What diagnosis would you give patient B?
5. What notation would you use to characterize Patient C’s karyotype?
6. What diagnosis would you give patient C?
Report
Submit your answers to the above questions in a MS Word .doc file.
Also research and include in your report a description of another human syndrome caused by an
abnormal number of chromosomes.
Grading Rubric
If all of the questions are satisfactorily addressed, then you earn the maximum number of 10
points for this report.