Page 42 - CB1.3 Genetic Varation sciPAD

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42 CB 1.3 GENETIC VARIATION
TRACKING GENES
Tracking Genes for Health - Cystic Fibrosis
Cystic fibrosis is a genetic disorder that results in the lungs becoming filled with a thick mucus. This
frequently-occurring disorder often leads to pneumonia and death during childhood.
The cystic fibrosis gene is recessive, which means that it is only expressed when an individual
inherits two copies of the gene (one from each parent). A carrier of the gene has only one copy
of the gene and does not have the disease.
By tracking the inheritance of the cystic fibrosis gene in a family using Punnett Squares and
pedigree charts, we can better understand the risk of the disease being passed down to future
generations and take appropriate measures to prevent it.
The pedigree chart below shows the inheritance of the disease through three generations of a
family.
17
1 2
3
11 12 13 14 15 16
4 5 6 7 8 9 10
Affected Female Affected Male Normal Female Normal Male
KEY
III
II
I
1. Use the pedigree chart to show that the cystic fibrosis gene is recessive. Support your
answer with:
•
reference to specific individuals from the pedigree chart.
•
a Punnett square.













2. Describe a benefit of tracking the inheritance of the cystic fibrosis gene. 


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