Table of contents
- 1. Introduction to Biology2h 42m
- 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 44m
- Introduction to Mendel's Experiments7m
- Genotype vs. Phenotype17m
- Punnett Squares13m
- Mendel's Experiments26m
- Mendel's Laws18m
- Monohybrid Crosses19m
- 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 Transport1h 2m
- 35. Soil37m
- 36. Plant Reproduction47m
- 37. Plant Sensation and Response1h 9m
- 38. Animal Form and Function1h 19m
- 39. Digestive System1h 10m
- 40. Circulatory System1h 57m
- 41. Immune System1h 12m
- 42. Osmoregulation and Excretion50m
- 43. Endocrine System1h 4m
- 44. Animal Reproduction1h 2m
- 45. Nervous System1h 55m
- 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
Genotype vs. Phenotype
Problem 3`
Textbook Question
The alleles found in haploid organisms cannot be dominant or recessive. Why?
a. Dominance and recessiveness describe which of two possible phenotypes are exhibited when two different alleles occur in the same individual.
b. Because only one allele is present, alleles in haploid organisms are always dominant.
c. Alleles in haploid individuals are transmitted like mitochondrial DNA or chloroplast DNA.
d. Most haploid individuals are bacteria, and bacterial genetics is completely different from eukaryotic genetics.

1
Understand the concept of dominance and recessiveness: These terms are used to describe the relationship between two alleles in a diploid organism, where one allele can mask the expression of another.
Recognize that haploid organisms have only one set of chromosomes, meaning they have only one allele for each gene.
Since there is only one allele present in haploid organisms, there is no second allele to compare it to, making the concepts of dominance and recessiveness irrelevant.
Consider the definition of dominance and recessiveness: These terms are used when two different alleles are present in the same individual, which is not the case in haploid organisms.
Conclude that option (a) is correct because dominance and recessiveness require two alleles to compare, which is not applicable in haploid organisms with only one allele per gene.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Haploid Organisms
Haploid organisms have a single set of chromosomes, meaning they possess only one allele for each gene. This contrasts with diploid organisms, which have two sets of chromosomes and thus two alleles for each gene. In haploids, the concept of dominance and recessiveness does not apply because there is no allele pair to compare; the single allele present directly determines the phenotype.
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Dominance and Recessiveness
Dominance and recessiveness are terms used to describe the relationship between alleles in diploid organisms. When two different alleles are present, the dominant allele's trait is expressed in the phenotype, while the recessive allele's trait is masked. This concept is irrelevant in haploid organisms, as they have only one allele per gene, eliminating the possibility of allele interaction.
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Dominant vs. Recessive Alleles
Genetic Transmission in Haploids
In haploid organisms, genetic transmission occurs through a single allele per gene, similar to the inheritance patterns seen in organelle DNA like mitochondrial or chloroplast DNA. This means that the genetic information is passed on without the complexity of allele interactions seen in diploid organisms, simplifying the inheritance pattern to a direct transmission of the single allele present.
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