Question

Lab Analysis Exploring Patterns of inheritance 3. Siekde sal di C-cell disease is a genetic condition used by an autosomal receive allele which af fects one in every 500 African A c hild born in the US. One in every en African Americans is a carrier for the Aluch e cell disease is caused by a single human gene, it is expressed throw many different effects throughout the body The presence of a recessive schedulele in humans causes the red blood cells to produce abnormal hemoglobin protein molecules which can link to ther and crystalline. This in turn causes the red blood cells to take on a side shaped form with aged edges, which can become destroyed by the body, clog the flow of blood in small blood vessels, and accumulate in the spleen. Multiple organs are damaged over time, and 100,000 people who are homozygous recessive die each year from this disease worldwide. a David and Linda want to start a family but are concerned about sickle-cell disease, since both of them have relatives who died from this disorder. They decide to make an appoint- ment with you, a well-known genetic counselor. What would be the first step you recom- mend to this couple? b. When the results of the genetic tests come back, you see that David is indeed a carrier for this condition, while Linda does not have a copy of the gene. At their follow-up visit, David is concerned about his carrier status. Complete the Punnett square below to show the probability of David and Linda having a child with sickle-cell disease. Use the letter "A" to symbolize this gene. A Sperm A LAA AA a Aa Aa David and Linda have % chance of having a child with sickle-cell disease. c. Suppose that both David and Linda had turned out to be carriers. Complete the Punnett square below to show the probability of David and Linda having a child who is also het- erozygous. A Sperm a AAA AA Eggs a aa aa d. Circle the heterozygous genotypes in the Punnett square.

Answer 1

A. A blood test can be done to test for the presence of Hemoglobin S which is a defective hemoglobin present in the RNCs due to mutation in the beta-globin gene. Presence of defective sickle cell gene also can be performed to know if the individual is a carrier. As the two individuals are not sufferers, the above carrier tests can be done to know if they are carriers.

B. Here A is the normal gene coding for normal hemoglobin. 'a' is the mutant gene coding for hemoglobin S. Since hemoglobin S is a recessive trait, we take 'a' as the allele and 'A' as the normal allele.

(Linda) AA x Aa (David) е ~ Сераять) A AAA a IAA | A AA - Normal like mother Aa Carrier like father.

All off spring are normal , So they have 0% chance of their children suffering from the disesae. But 50% are carriers.

C.

D. The heterozygous offspring are circled above. 50% chances of the offsprng being heterozygous and carriers.