Table of contents
- 1. Introduction to Genetics51m
- 2. Mendel's Laws of Inheritance3h 37m
- 3. Extensions to Mendelian Inheritance2h 41m
- 4. Genetic Mapping and Linkage2h 28m
- 5. Genetics of Bacteria and Viruses1h 21m
- 6. Chromosomal Variation1h 48m
- 7. DNA and Chromosome Structure56m
- 8. DNA Replication1h 10m
- 9. Mitosis and Meiosis1h 34m
- 10. Transcription1h 0m
- 11. Translation58m
- 12. Gene Regulation in Prokaryotes1h 19m
- 13. Gene Regulation in Eukaryotes44m
- 14. Genetic Control of Development44m
- 15. Genomes and Genomics1h 50m
- 16. Transposable Elements47m
- 17. Mutation, Repair, and Recombination1h 6m
- 18. Molecular Genetic Tools19m
- 19. Cancer Genetics29m
- 20. Quantitative Genetics1h 26m
- 21. Population Genetics50m
- 22. Evolutionary Genetics29m
3. Extensions to Mendelian Inheritance
Variations of Dominance
0:27 minutes
Problem 8g
Textbook Question
Textbook QuestionTwo genes interact to produce various phenotypic ratios among F₂ progeny of a dihybrid cross. Design a different pathway explaining each of the F₂ ratios below, using hypothetical genes R and T and assuming that the dominant allele at each locus catalyzes a different reaction or performs an action leading to pigment production. The recessive allele at each locus is null (loss-of-function). Begin each pathway with a colorless precursor that produces a white or albino phenotype if it is unmodified. The ratios are for F₂ progeny produced by crossing wild-type F₁ organisms with the genotype RrTt.
9/16 dark blue : 6/16 light blue : 1/16 white
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Dihybrid Cross
A dihybrid cross involves two traits, each controlled by different genes, typically represented by two pairs of alleles. In this case, the genes R and T are being studied, where each gene can have a dominant or recessive allele. The phenotypic ratios observed in the offspring (F₂ generation) arise from the independent assortment of these alleles during gamete formation, leading to a variety of combinations in the progeny.
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Punnet Square
Phenotypic Ratios
Phenotypic ratios describe the relative frequencies of different phenotypes in the offspring resulting from a genetic cross. In the given scenario, the ratios of 9/16 dark blue, 6/16 light blue, and 1/16 white indicate how the interactions between the alleles of genes R and T influence pigment production. Understanding these ratios is crucial for predicting the outcomes of genetic crosses and the underlying genetic mechanisms.
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Mutations and Phenotypes
Gene Interaction
Gene interaction occurs when the effects of one gene are modified by one or several other genes, leading to a combined effect on the phenotype. In this case, the dominant alleles of genes R and T catalyze different reactions that contribute to pigment production from a colorless precursor. The specific interactions between these genes can result in various phenotypes, as seen in the distinct ratios of the F₂ progeny.
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Interacting Genes Overview
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