In the genetics lab, we used a simulation and defined what a chromosome is, and we took a look
at its structure and the copying and distribution of chromosomes during cell division.
In this lab, we want to take a closer look at human chromosomes and the concept of non-
disjunction by looking at actual photos of human chromosomes. These photos are called
karyotypes and these are used in clinical medicine. Karyotypes from a single cell are used in the
hospital clinic to determine genetic abnormalities due to non-disjunction. Samples are taken from
parents or unborn children and cells are cultured (grown in the lab) and then analyzed to see if
the full complement of chromosomes are in each cell. Here is a quote from a fertility clinic
website describing the karyotyping procedure:
“A karyotype can be performed on any tissue but most often it is done from a blood
sample, a sample of amniotic fluid or a piece of placenta obtained through chorionic villi
sampling. Karyotyping is a complex process that involves growing the cells, obtaining
the chromosomes, staining and analyzing the chromosomes and reporting the results. A
karyotype is an actual photograph of the chromosomes from one cell.”
Why do the cells have to be cultured? Think about it and see the answer at the bottom of page 2.
Since in some cases individual genetic abnormalities are due to non-disjunction of certain
chromosomes, each of the 23 pairs of chromosomes is observed so that abnormalities can be
detected. A complete set of chromosomes is determined by locating each pair of the 23
chromosomes. How can this be done if they all look the same? They can be the same because
each pair of chromosomes is actually very different from all other pairs. For instance,
chromosomes can differ in appearance by their length, the position of their centromere, and their
banding pattern.
The banding pattern on a chromosome is a series of stripes seen on chromosomes and is the
result of the way the DNA is packed into the chromosome. Chromosome pairs show identical (or
nearly identical) banding patterns. In this activity, you will be completing an actual karyotype by
observing and arranging chromosomes in clinically-derived karyotype samples.
Lewis text: ch. 13
Proceed to this website provided in the assigned Module: Week’s Learn section: Interact:
Karyotyping Activity. Read the “Introduction” and “Patient Histories,” then complete the
karyotypes. After you successfully complete them, you will be asked to choose the genetic
abnormality present in the patient sample. Write down your answers and then answer the
questions below in the fill-in-the-blank problem section.
Each of the questions in Karyotyping and Genetics Testing Template involves a single-word
answer or number answer. Upload your answers and number them 1–3.

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