Karyotyping Activity

Patient C's Karyotype

Congratulations! You successfully completed Patient C's Karyotype. Next, interpret the karyotype and make a diagnosis. Patient C's completed karyotype is at the bottom of the page for reference.

On a separate piece of paper, answer the following 2 questions.

Interpreting the karyotype

Lab technicians compile karyotypes and then use a specific notation to characterize the karyotype. This notation includes the total number of chromosomes, the sex chromosomes, and any extra or missing autosomal chromosomes. For example, 47, XY, +18 indicates that the patient has 47 chromosomes, is a male, and has an extra autosomal chromosome 18. 46, XX is a female with a normal number of chromosomes. 47, XXY is a patient with an extra sex chromosome.

C 1. What notation would you use to characterize Patient C's karyotype?

Making a diagnosis

The next step is to either diagnose or rule out a chromosomal abnormality. In a patient with a normal number of chromosomes, each pair will have only two chromosomes. Having an extra or missing chromosome usually renders a fetus inviable. In cases where the fetus makes it to term, there are unique clinical features depending on which chromosome is affected. Listed below are some syndromes caused by an abnormal number of chromosomes.

C 2. What diagnosis would you give patient C?

DiagnosisChromosomal Abnormality
Normal # of chromosomespatient's problems are due to something other than an abnormal number of chromosomes.
Klinefelter's Syndromeone or more extra sex chromosomes (i.e., XXY)
Down's SyndromeTrisomy 21, extra chromosome 21
Trisomy 13 Syndromeextra chromosome 13

Patient C's History

Patient C died shortly after birth, with a multitude of anomalies, including polydactyly and a cleft lip. Chromosomes were obtained from a tissue sample.

Patient C's Karyotype


_______
1

________
2

________
3

________
4

________
5

________
6

________
7

________
8

________
9

________
10

________
11

________
12

________
13

________
14

________
15

________
16

________
17

________
18

________
19

________
20

________
21

________
22

________
XX/XY


The Biology Project
University of Arizona
Saturday, August 17, 1996
denicew@u.arizona.edu

http://www.biology.arizona.edu
All contents copyright © 1996. All rights reserved.