Karyotyping+Activity

[|Taking a Sample Karyotype] <- Link leads back to website where activity was done if you want to visit it yourself!

**//__A. Introduction__//**
Karyotyping is one of many techniques that allow us to look for several thousand possible genetic diseases in humans. A karyotype analysis usually involves blocking cells in mitosis and staining the condensed chromosomes with Giemsa dye. The dye stains regions of chromosomes that are rich in the base pairs Adenine (A) and Thymine (T), producing a dark band. A common misconception is that bands represent single genes, but in fact the thinnest bands contain over a million base pairs and potentially hundreds of genes. For example, the size of one small band is about equal to the entire genetic information for one bacterium! 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. This exercise is a simulation of human karyotyping using digital images of chromosomes from actual human genetic studies. In this activity, you will be arranging chromosomes into a completed karyotype, 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. We had to imagine that we were performing these very analyses for real people, and that our conclusions would drastically affect their lives. This made the activity much more interesting and we advise you do the same. There were also a few questions for us to answer as well.

**//__B. The Assignment/Task__//**
This exercise is designed as an introduction to genetic studies on humans. We evaluated 3 patients' case histories, completed their karyotypes, and diagnosed any missing or extra chromosomes. Then we conducted in-depth research on the internet to find web sites that cover some aspect of human genetics, also learning about various treatment options.

**//__C. Results/Answers to Questions (Turn back to the site for the patient histories and any other relevant information.)__//**
__//**A 1. What notation would you use to characterize Patient A's karyotype?**//__ This patient can be identified with the notation of __//**47, XX, +21**//__. This indicates that the patient is a female with 47 chromosomes, possessing an extra copy of chromosome 21.

Patient A is the nearly-full-term fetus of a forty year old female. Chromosomes were obtained from fetal epithelial cells acquired through amniocentesis. Having an extra or missing chromosome usually renders a fetus inviable but, based on an analysis of patient A's karyotype, we diagnosed this patient with the likelihood of developing **//__Down's Syndrome__//** (Otherwise known as Trisomy 21).
 * //__A 2. What diagnosis would you give patient A?__//**

__//**B 1. What notation would you use to characterize Patient B's karyotype?**//__ This patient can be identified with the notation of __**47, XXY**__. This notation indicates that the patient is a male with 47 chromosomes, possessing an extra sex chromosome.

__//**B 2. What diagnosis would you give patient B?**//__ Patient B is a 28 year old male who is trying to identify a cause for his infertility. Chromosomes were obtained from nucleated cells in the patient's blood. He was diagnosed with **//__Klinefelter's Syndrome.__//**

This patient can be identified with the notation of __//**47,XY, +13**//__. This indicates that the patient is a male with 47 chromosomes, possessing an extra copy of chromosome 13.
 * //__C 1. What notation would you use to characterize Patient C's karyotype?__//**

Unfortunately, Patient C died shortly after birth, with a multitude of anomalies, including polydactyly (Development of extra fingers) and a cleft lip. Chromosomes were obtained from a tissue sample. As a result of possessing an extra copy of chromosome 13, the patient was diagnosed with __//**Trisomy 13 syndrome**//__. A complication of this disorder could have been the possible development of [|Varadi-Papp Syndrome].
 * //__C 2. What diagnosis would you give patient C?__//**

D. Further Research See also:
 * [|University of Kansas Medical Center]