Sickle Cell. Scientific Investigation

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Kathryn Rich
5 years ago
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Scientific Investigation Red blood cells are oval and ave a biconcave sape, giving tem te appearance of an inner tube witout te ole. Teir sape gives tem flexibility as tey pass into small capillaries.

1 Scientific Investigation Red blood cells are oval and ave a biconcave sape, giving tem te appearance of an inner tube witout te ole. Teir sape gives tem flexibility as tey pass into small capillaries. Red blood cells are red because of te protein emoglobin in teir cytoplasm. emoglobin contains te element iron, wic bonds to oxygen. Red blood cells primary function is to transport oxygen from te lungs to cells in te body. A genetic disease called sickle cell anemia affects te protein emoglobin in red blood cells of umans. It is caused by a mutated version of te gene tat elps make emoglobin. Te mutation is caused by a substitution of a nitrogenous base in te DNA. Te normal DNA sequence coding for glutamic acid is switced to te amino acid valine in te mutated gene. Tis single amino acid difference in te DNA segment causes te protein in emoglobin to cange sape and clump togeter, wic gives te red blood cell a sickle sape. Te distorted sape of te emoglobin prevents te cell from carrying as many oxygen molecules as a normal-saped cell. It also makes te cell more rigid and prevents it from passing easily troug narrow passages suc as capillaries. Sickle-saped red blood cells often get stuck in tese small blood vessels and may break apart, causing pain. Tey do not live as long as normal, ealty red blood cells and are not replaced as quickly, leaving te individual wit a lower ability to supply oxygen to cells and critical organs suc as te brain, kidneys, eart, and lungs. Sickle cell anemia is an autosomal recessive disorder. An individual tat inerits two versions of te mutated gene, one from eac parent, will ave te disease. People wo inerit tis disease often die before te age of 40; in underdeveloped countries, tey may die before reacing adultood. Individuals wo inerit one version of te normal emoglobin gene and one mutated version of te gene ave a condition called sickle cell trait. Tese individuals do not ave te disease, but tey can pass te sickle emoglobin gene to teir cildren. Sickle cell disease is most common among people of Africa, India, te Middle East, te Mediterranean, and te Caribbean. Te prevalence of te mutated gene in tese populations is associated wit te presence of te Anopeles mosquitoes and a Plasmodium parasite tat uses te mosquito as a ost. Tese mosquitoes carry te parasite tat causes malaria. Wen te mosquito bites an individual, te parasite is injected into te bloodstream and infects red blood cells. Once inside te person, te parasite continues to multiply and infect more red blood cells. Te infected individual develops ig fevers and recurring cills tat may lead to deat. owever, individuals wo ave te sickle cell trait are resistant to malaria. Tis resistance is due to teir red blood cells containing some abnormal emoglobin tat will sickle wen infected by te malaria parasite. Te spleen removes te sickle-saped cells and, as a result, removes te infected cells and parasite. 1

2 In your lab journal, address te following investigation: Step 1: Question. Step 2. Relevance. Step 3. Variables, if applicable. Independent variable (also known as te manipulated variable): Dependent variable (also known as te responding variable): Control variable (s) group (also known as constants): Step 4 ypotesis. Is a ypotesis needed? If so, wat is it? Step 5. Materials. Step 6. Safety Considerations. Step 7a. Procedure Sample procedure Simulation 1: omozygous 100% Letal 1. Label a paper bag Starting Population. Place 50 red beans and 50 pinto beans into te bag. Let te red beans represent te allele for normal emoglobin () and te pinto bean represent te allele for sickle cell (). 2. Calculate te allele frequency for and by counting te number of eac allele and dividing by te total number of alleles in te population. Record tese data in te data table. 3. In tis simulation, assume tat te genotype represents individuals wit te sickle cell disease and tat individuals born wit tis genotype die before reproductive age and do not pass teir genes on to te next generation. 4. Randomly select 2 beans from te bag to represent one. Place a tally mark in te correct row of te table. Return te beans back to te bag and mix between. Repeat until you ave a total of 50 recorded. Tese 50 are te First Generation. 5. Calculate te allele frequencies for te first generation of. To calculate te frequency of, use (2(# of individuals) + # of individuals)/total # of alleles. To calculate te frequency of, use (# of individuals)/total # of alleles. Use tis allele frequency to create your first generation wit 50 individuals and 100 alleles. For example, if te allele frequency for was 0.82, place 82 red beans into te bag. Te remaining 18 alleles must terefore be, so put 18 pinto beans in te bag. 6. Repeat steps 4 and 5 for anoter two generations recording te results in te Second Generation and Tird Generation tables, respectively. 7. Record your results in te summary page for Simulation 1. 2

3 Step 8a. Data Collection for Simulation 1: omozygous 100% Letal First Generation Genotype Tally Marks Frequency Use te allele frequency above to create a population of 50 individuals, wit 100 alleles. # of red beans # of pinto beans Second Generation Genotype Tally Marks Frequency Use te allele frequency above to create a population of 50 individuals, wit 100 alleles. # of red beans # of pinto beans Tird Generation Genotype Tally Marks Frequency 3

4 Step 8a. Data Collection for Simulation 1: omozygous 100% Letal. continued Simulation 1: omozygous 100% Letal Summary Page Starting Population First Generation Second Generation Tird Generation 4

5 Step 7b. Procedure Sample Procedure Simulation 2: eterozygous Advantage 1. Label a paper bag Starting Population. Place 50 red beans and 50 pinto beans into te bag. Let te red beans represent te allele for normal emoglobin () and te pinto bean represent te allele for sickle cell (). 2. Calculate te allele frequency for and by counting te number of eac allele and dividing by te total number of alleles in te population. Record tese data in te summary page. 3. In tis simulation, assume te following: Only alf (50%) of individuals wit genotype survive and reproduce. All individuals (100 %) wit genotype survive to reproduce. No individuals wit te genotype reproduce. 4. Randomly select 2 beans from te bag to represent one. Place a tally mark in te correct row of te table. Return te beans back to te bag and mix between. Repeat until you ave a total of 50 recorded. Tese 50 are te First Generation. 5. Calculate te allele frequencies for te first generation of. To calculate te frequency of, use ((# of individuals) + (# of individuals))/total # of alleles. To calculate te frequency of, use (# of individuals)/total # of alleles. Use tis allele frequency to create your first generation wit 50 individuals and 100 alleles. For example, if te allele frequency for was 0.82, place 82 red beans into te bag. Te allele frequency for ad to be 0.18, so place 18 pinto beans into te bag. 6. Repeat steps 4 and 5 for anoter two generations, recording te results in te Second Generation and Tird Generation tables, respectively. 7. Record your results in te summary page for Simulation 2. 5

6 Step 8b. Data Collection for Simulation 2: eterozygous Advantage First Generation Genotype Tally Marks Frequency Use te allele frequency above to create a population of 50 individuals, wit 100 alleles. # of red beans # of pinto beans Second Generation Genotype Tally Marks Frequency Use te allele frequency above to create a population of 50 individuals, wit 100 alleles. # of red beans # of pinto beans Tird Generation Genotype Tally Marks Frequency 6

7 Step 8B. Data Collection for Simulation 2: eterozygous Advantage, continued Simulation 2: eterozygous Advantage Data Tables Starting Population First Generation Second Generation Tird Generation 7

8 Step 9: Data analysis In your lab journal, create a grap of te data results from eac simulation representing allele frequencies in eac generation. Use different-colored pencils to draw your graps. Eac grap sould ave a title wit te x-axis labeled Number of Generations and te y-axis labeled Frequency In your lab journal, address te following questions: 1. ow did te frequency of te sickle cell allele () cange from te starting population to te first generation in Simulation 1? ow did it cange wit eac of te next two generations of? 2. ow did te frequency of te sickle cell allele () cange from te starting population to te first generation in Simulation 2? ow did it cange wit eac of te next two generations of? 3. In bot simulations, te omozygous condition for sickle cell disease was 100% letal. ow did te frequency for te allele contrast in eac simulation? 4. Wic simulation would represent regions of Africa wit a ig population of Plasmodiuminfected Anopeles mosquitoes? Explain. 5. ow is tis simulation an example of evolution? Step 10: Conclusion Write a scientific explanation of ow selective pressures witin tis environment can led to canges in allele frequencies witin tis population. 8

9 Rubric for writing a scientific explanation Points Awarded Claim Not applicable. Answers te question and is accurate based on data. No claim, or does not answer te question. Evidence Cites data and patterns witin te data. Uses labels accurately. Cites data from te data source but not witin te context of te prompt. No evidence, or cites canges but does not use data from data source. Reasoning Cites te scientifically accurate reason using correct vocabulary and connects tis to te claim. Sows accurate understanding of te concept. Cites a reason, but it is inaccurate or does not support te claim. Reasoning does not use scientific terminology or uses it inaccurately. No reasoning, or restates te claim but offers no reasoning. Rebuttal Rebuttal provides reasons for different data or outliers in te data. Can also provide relevance to te real world or oter uses for te findings. Rebuttal is not connected to te data or is not accurate. Does not offer a rebuttal. 9

Name: Key: E = brown eye color (note that blue eye color is still represented by the letter e, but a lower case one...this is very important)

Name: Key: E = brown eye color (note that blue eye color is still represented by the letter e, but a lower case one...this is very important) MONOHYBRID CROSS v2 Name: Introduction A gamete is te egg or sperm cell tat is produced by meiosis. A gamete contains te aploid number of cromosomes (in a uman tis number is 23). In eac of tese cromosomes