Sickle Cell Analysis Directions: Read the information below to complete the two tables. A person with sickle-cell disease has the genotype: Hb s Hb s. People who have this condition have two abnormal genes, one inherited from each parent. Individuals without sickle cell can have the genotypes Hb N Hb s or Hb N Hb N. The N stands for Normal and the S stands for Sickle. Below are the sections of the DNA sequences of a normal hemoglobin gene and the mutated gene that causes sickle cell disease. Normal Gene DNA Sequence CAC GTG GAC TCA GGA GAA CTC Mutated Gene DNA Sequence CAC GTG GAC TCA GGA GTA CTC...
Genotype of normal individual: Sequence of DNA of normal individual: Sequence of complementary DNA of normal individual: Sequence of MRNA of normal individual: Sequence of the Amino Acids of a normal individual: Genotype of individual with Sickle Cell: Sequence of DNA of individual with Sickle Cell: Sequence of complementary DNA of individual with Sickle Cell : Sequence of MRNA of individual with Sickle Cell: Sequence of the Amino Acids of an individual with Sickle Cell:
Punnett Square Practice Directions: Fill in a punnett square to show the probability of phenotypes if: 1. Normal individuals that are heterozygous and homozygous dominant had children Hb N Hb N = Hb N Hb s = 2. Normal individuals that are both heterozygous had children Hb N Hb N = Hb N Hb s = Hb s Hb s = 3. Individuals with Sickle Cell that are heterozygous and homozygous recessive Hb N Hb s = Hb s Hb s = 4. Individuals with Sickle Cell that are both homozygous recessive Hb N Hb s = Hb s Hb s =
Directions: Read and annotate. Then complete the questions. Hemoglobin and Red Blood Cell Abnormalities in Sickle-Cell Disease Each year, about one in 625 African American children is born with sickle-cell disease. This disease is caused by a mutation in the gene that codes for hemoglobin, the protein that carries oxygen in red blood cells. The mutation changes the amino acid, glutamic acid into valine, which changes the shape of hemoglobin. When the oxygen supply in the blood is low, these abnormal hemoglobin molecules clump together. Normal hemoglobin molecules remain separate. 1. What is the role of hemoglobin in the blood? 2. What happens to the hemoglobin molecule because of the mutation? 3. Below is an image of what normal hemoglobin molecules look like. Based on the description in the paragraph above, draw what the mutated hemoglobin molecule would look like in the blank box. Normal Hemoglobin Molecule Mutated Hemoglobin Molecule
In a person with sickle-cell disease, the clumping of the hemoglobin molecules at low oxygen levels causes the red blood cells to become long and rigid like a sickle instead of remaining round and flexible. (Figure 2) That change in cell shape causes a variety of problems in the body. For example, as cells become sickled, they block small blood vessels (Figure 3). This causes pain and damage to the areas that do not receive an adequate blood supply. The long-term effect of repeated blockages may permanently damage a person s organs, like the heart, kidneys, and brain. However, with good medical care, however, many people with sickle-cell disease can live reasonably normal lives. Figure 2 4. Why do people with Sickle Cell experience pain? 5. What are some of the long term effects of someone who has Sickle Cell? In a strange twist, it can actually be advantageous to have sickle cell disease. Individuals with sickle cell actually have immunity to malaria. Malaria is caused by a parasite that is transmitted to humans by mosquitos. When a person gets bitten by a mosquito, the malaria parasite infects and destroys red blood cells, which can result in chills, fever, vomiting, and severe headaches. However, the parasite cannot infect individuals with sickle cell, or carriers of the sickle cell allele, so these individuals do not get sick from malaria. 6. What is an advantage that those with Sickle Cell or those who are carriers have over others? Figure 3
Directions: Analyze the pedigree below on sickle cell and answer the questions. 1. How many generations are represented in the chart for sickle-cell anemia? 2. How many carriers of the sickle-cell trait are in each generation? 3. How many people in the family were born with sickle-cell anemia? 4. From which parent did the second-generation children inherit the sickle-cell gene? 5. How many children did 1 and 2 have? How many Boys? How many Girls? 6. In which generation did sickle-cell anemia first show? 7. Draw a Punett square to show If person 8 married a women who was a carrier for sickle cell what is the probability that a child will come out with Sickle cell? What is the probability they will not be affected? 8. What can you determine about a family using a pedigree chart? (Be specific)