Table of contents
- 1. Introduction to Biology2h 40m
- 2. Chemistry3h 40m
- 3. Water1h 26m
- 4. Biomolecules2h 23m
- 5. Cell Components2h 26m
- 6. The Membrane2h 31m
- 7. Energy and Metabolism2h 0m
- 8. Respiration2h 40m
- 9. Photosynthesis2h 49m
- 10. Cell Signaling59m
- 11. Cell Division2h 47m
- 12. Meiosis2h 0m
- 13. Mendelian Genetics4h 41m
- Introduction to Mendel's Experiments7m
- Genotype vs. Phenotype17m
- Punnett Squares13m
- Mendel's Experiments26m
- Mendel's Laws18m
- Monohybrid Crosses16m
- Test Crosses14m
- Dihybrid Crosses20m
- Punnett Square Probability26m
- Incomplete Dominance vs. Codominance20m
- Epistasis7m
- Non-Mendelian Genetics12m
- Pedigrees6m
- Autosomal Inheritance21m
- Sex-Linked Inheritance43m
- X-Inactivation9m
- 14. DNA Synthesis2h 27m
- 15. Gene Expression3h 20m
- 16. Regulation of Expression3h 31m
- Introduction to Regulation of Gene Expression13m
- Prokaryotic Gene Regulation via Operons27m
- The Lac Operon21m
- Glucose's Impact on Lac Operon25m
- The Trp Operon20m
- Review of the Lac Operon & Trp Operon11m
- Introduction to Eukaryotic Gene Regulation9m
- Eukaryotic Chromatin Modifications16m
- Eukaryotic Transcriptional Control22m
- Eukaryotic Post-Transcriptional Regulation28m
- Eukaryotic Post-Translational Regulation13m
- 17. Viruses37m
- 18. Biotechnology2h 58m
- 19. Genomics17m
- 20. Development1h 5m
- 21. Evolution3h 1m
- 22. Evolution of Populations3h 52m
- 23. Speciation1h 37m
- 24. History of Life on Earth2h 6m
- 25. Phylogeny2h 31m
- 26. Prokaryotes4h 59m
- 27. Protists1h 12m
- 28. Plants1h 22m
- 29. Fungi36m
- 30. Overview of Animals34m
- 31. Invertebrates1h 2m
- 32. Vertebrates50m
- 33. Plant Anatomy1h 3m
- 34. Vascular Plant Transport2m
- 35. Soil37m
- 36. Plant Reproduction47m
- 37. Plant Sensation and Response1h 9m
- 38. Animal Form and Function1h 19m
- 39. Digestive System10m
- 40. Circulatory System1h 57m
- 41. Immune System1h 12m
- 42. Osmoregulation and Excretion50m
- 43. Endocrine System4m
- 44. Animal Reproduction2m
- 45. Nervous System55m
- 46. Sensory Systems46m
- 47. Muscle Systems23m
- 48. Ecology3h 11m
- Introduction to Ecology20m
- Biogeography14m
- Earth's Climate Patterns50m
- Introduction to Terrestrial Biomes10m
- Terrestrial Biomes: Near Equator13m
- Terrestrial Biomes: Temperate Regions10m
- Terrestrial Biomes: Northern Regions15m
- Introduction to Aquatic Biomes27m
- Freshwater Aquatic Biomes14m
- Marine Aquatic Biomes13m
- 49. Animal Behavior28m
- 50. Population Ecology3h 41m
- Introduction to Population Ecology28m
- Population Sampling Methods23m
- Life History12m
- Population Demography17m
- Factors Limiting Population Growth14m
- Introduction to Population Growth Models22m
- Linear Population Growth6m
- Exponential Population Growth29m
- Logistic Population Growth32m
- r/K Selection10m
- The Human Population22m
- 51. Community Ecology2h 46m
- Introduction to Community Ecology2m
- Introduction to Community Interactions9m
- Community Interactions: Competition (-/-)38m
- Community Interactions: Exploitation (+/-)23m
- Community Interactions: Mutualism (+/+) & Commensalism (+/0)9m
- Community Structure35m
- Community Dynamics26m
- Geographic Impact on Communities21m
- 52. Ecosystems2h 36m
- 53. Conservation Biology24m
13. Mendelian Genetics
Autosomal Inheritance
0:41 minutes
Problem 9
Textbook Question
Textbook QuestionKaren and Steve each have a sibling with sickle-cell disease. Neither Karen nor Steve nor any of their parents have the disease, and none of them have been tested to see if they carry the sickle-cell allele. Based on this incomplete information, calculate the probability that if this couple has a child, the child will have sickle-cell disease.
Verified step by step guidance
1
Identify the inheritance pattern: Sickle-cell disease is inherited in an autosomal recessive manner. This means that a person must inherit two copies of the sickle-cell allele (one from each parent) to express the disease.
Determine the genotype of the siblings with the disease: Since sickle-cell disease is autosomal recessive and the siblings have the disease, they must have the genotype ss (where 's' represents the sickle-cell allele).
Analyze the parents' genotypes: Since neither Karen's nor Steve's parents have the disease, but they have children who do, each parent must be a carrier of one sickle-cell allele. Therefore, each parent's genotype must be Ss (where 'S' represents the normal allele).
Calculate the probability of Karen and Steve being carriers: Since both sets of parents are carriers (Ss), Karen and Steve each have a 2/3 chance of being a carrier themselves, because the possible genotypes they could inherit are SS (1/4 chance) or Ss (3/4 chance), but we exclude SS as a possibility since we know they have a sibling with ss.
Determine the probability of their child having sickle-cell disease: If both Karen and Steve are carriers (each with a probability of 2/3), the probability that both pass the sickle-cell allele to their child is (2/3) * (2/3) * (1/4) = 1/9. This calculation comes from the probability that both are carriers multiplied by the probability that both pass on the sickle-cell allele (1/4, as each can pass on either S or s with equal probability).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Sickle-Cell Disease Genetics
Sickle-cell disease is an autosomal recessive disorder caused by a mutation in the HBB gene, leading to abnormal hemoglobin. Individuals with two copies of the sickle-cell allele (homozygous recessive) exhibit the disease, while those with one copy (heterozygous) are carriers but do not show symptoms. Understanding this inheritance pattern is crucial for calculating the probability of offspring inheriting the disease.
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Punnett Square
A Punnett square is a diagram used to predict the genetic makeup of offspring from two parents. It illustrates the possible combinations of alleles that can result from the mating of two individuals. By using a Punnett square, one can determine the likelihood of a child inheriting specific traits, such as sickle-cell disease, based on the genotypes of the parents.
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Carrier Probability
In this scenario, since neither Karen nor Steve has sickle-cell disease, they could be carriers of the sickle-cell allele. The probability of them being carriers can be inferred from their siblings' conditions. If both siblings have sickle-cell disease, it suggests that both parents are likely carriers, which affects the probability of their child inheriting the disease. Understanding carrier status is essential for calculating the risk of the child having sickle-cell disease.
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