Part II: Inheritance of Traits or Genetic Disorders Background: Cystic fibrosis

Question

Part II: Inheritance of Traits or Genetic Disorders

Background: Cystic fibrosis is an inherited disease that affects the respiratory, digestive, or reproductive systems of the body, with symptoms ranging from mild to severe. Bob and Sally are recently married. Upon deciding to plan a family, both Sally and Bob find out that they are both heterozygous for cystic fibrosis, but neither of them has symptoms of the disorder.

Assignment details: Complete a Punnett Square for cystic fibrosis for this couple using the following alleles: C = normal allele; and c = allele for cystic fibrosis.

Complete the Punnett Square in the graphic organizer.

Also answer the following questions:
Based on the Punnett square, calculate chances (percentages) for the following:

•for having a healthy child (not a carrier)
•a child that is a carrier for the cystic fibrosis trait
•a child with cystic fibrosis
Be sure to submit these percentages as part of your assignment in the Graphic Organizer.

Explanation / Answer

I'm not too sure how you want it done in a graphic organizer, but this is how its done
Since both parents are heterozygotes, there genotype is Cc. If they were homozygous dominant, they would be CC, and if they had cystic fibrosis, they would be homozygous recessive, and probably would not live to the age where they could have children.

So we have, Dad x Mom=Cc X Cc
The possible combinations are CC (healthy), 2Cc (carrier), and cc (sick).
The chart looks like this:

------C------c-

-C---CC----Cc-

-c----Cc----cc-

The baby can be 1 of three conditions. It has a 50% chance of being a carrier, and 25% chance of being either healthy or sick. As for percentage of being healthy, that's tricky because people that are heterozygous carry the allele but never show any symptoms of the disease. This is known as the heterozygous advantage.

Hope this helps, please rate.

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