Biology Lab

Biology 1001

Karyotyping Lab (5 pts.)

 

http://www.biology.arizona.edu/human_bio/activities/karyotyping/karyotyping.html

 

The Biology Project through The University of Arizona has an interactive exercise on human karyotyping. The first page you will encounter includes the following material (some additional details for YOUR assignment are different than those listed on the website and are highlighted in red at the bottom of this page).

 

This exercise is a simulation of human karyotyping using digital images of chromosomes from actual human genetic studies. You will be arranging chromosomes (by clicking and dragging) into a completed karyotype (an organized display – or image- of the chromosomes of one cell of the organism) and interpreting your findings just as if you were working in a genetic analysis program at a hospital or clinic. Karyotype analyses are performed over 400,000 times per year in the U.S. and Canada. Imagine that you were performing these analyses for real people, and that your conclusions would drastically affect their lives.

 

G Banding:

In the cell during the cellular division process of mitosis, the 23 pairs (a total of 46 individuals) of human chromosomes condense and are visible with a light microscope. A karyotype analysis usually involves blocking (halting, slowing cell division) cells in mitosis and staining the condensed chromosomes with a dye called Giemsa. Giemsa stain is commonly used in molecular/microbiological fields to stain many things, but in this application, Giemsa stains regions of chromosomes that are rich in the DNA nitrogenous base pairs Adenine (A) and Thymine (T) producing a dark colored stripe, called a G-band. A common misconception is that G-bands represent single genes, but in fact the thinnest G-bands contain over 1,000,000 (one million) base pairs and potentially hundreds of genes, in one tiny little G-band. The size of one small G-band is equivalent to the entire genetic information for one bacterium (for example, ONE E. coli in the gut).

 

The analysis involves comparing chromosomes for their length, the placement of centromeres (areas where the two chromatids are joined), and the location and sizes of G-bands. The assignment involves electronically completing the karyotype for 3 individuals and look for abnormalities that could explain the physical characteristics (called the phenotype) of the individual.

 

The Assignment:

Evaluate 3 patients’ case histories by:

 

1. Completing the karyotypes for each of the 3 patients, as instructed online at the link above.

 

2. Diagnose any missing or extra chromosomes in each individual’s genetic profile as instructed online and complete the questions on the website for each patient.

 

3. After completing questions 1 and 2, you will submit 1 written response per patient (3 responses total for this portion)

* Each minimum ½ page in length, typed single spaced detailing what you learned about each patient.

 

4. Conduct research from 3 reputable web sites that cover some interesting aspect of human genetics and karyotyping (do not use Wikipedia) and submit 1 written response about the information you discover

* 1 page in length total, single spaced

* Be very careful to use your own words. Plagiarism will result in a zero on the assignment.

 

 

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