Page 215 - Canadian BC Science 9

By analyzing karyotypes, geneticists can determine when a whole chromosome mutation has occurred. Understanding which chromosomes have been affected helps physicians diagnose and treat patients with genetic disorders or syndromes. A syndrome is a particular disease or disorder with a specific group of symptoms that occur together. One example is Down syndrome, which is one of the most frequently occurring types of chromosome mutations. Individuals with Down syndrome (Figure 6.12) have characteristic facial features and shorter stature and may be prone to developing heart defects and diseases such as Alzheimer’s and leukemia. Ninety-five percent of the cases of Down syndrome are caused by an extra 21st chromosome (Figure 6.13).
Figure 6.12 People with Down syndrome are active Figure 6.13 participants in their communities. syndrome
Analyzing a Karyotype
Geneticists study karyotypes to determine if any chromosome mutations have occurred. In this activity, you will analyze a karyotype of Edwards syndrome.
What to Do
1. Examine the karyotype of Edwards syndrome (right).
2. Count and record the total number of chromosomes
and chromosome pairs.
3. Determine whether the individual is male or female.
What Did You Find Out?
1. What chromosome error did you identify?
2. (a) Would karyotyping identify a gene mutation?
The karyotype of a person with Down
Find Out ACTIVITY
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6 7 8 9 10 11 12
13 14 15 16 17 18
19 20 21 22 X Y
6-1B
(b) Whyorwhynot?
Chapter 6 Meiosis is the basis of sexual reproduction. • MHR 197