Which of the following gametes cannot be formed from the genotype AaBBCc?
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
Understanding Independent Assortment
Problem 3a
Textbook Question
A pure-breeding tall plant producing oval fruit as described in Problem 2 is crossed to a pure-breeding short plant producing round fruit.
The F₁ are crossed to short plants producing oval fruit. What are the expected proportions of progeny phenotypes?

1
Determine the genotypes of the pure-breeding parents. A pure-breeding tall plant producing oval fruit can be represented as TTFF (where T = tall, t = short, F = oval, f = round). A pure-breeding short plant producing round fruit can be represented as ttff.
Perform the first cross between the pure-breeding parents (TTFF x ttff). Use a Punnett square to determine the genotypes of the F₁ generation. All F₁ offspring will be heterozygous for both traits (TtFf), as they inherit one allele from each parent.
Cross the F₁ plants (TtFf) with short plants producing oval fruit (ttFf). This is a test cross, and you will need to consider the independent assortment of the two traits. Set up a Punnett square for the cross TtFf x ttFf, considering all possible combinations of alleles.
Determine the phenotypes of the progeny based on the genotypes from the Punnett square. Recall that T (tall) is dominant over t (short), and F (oval) is dominant over f (round). For each genotype, assign the corresponding phenotype.
Calculate the expected proportions of each phenotype by counting the occurrences of each phenotype in the Punnett square and dividing by the total number of progeny. This will give you the expected phenotypic ratios.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Mendelian Genetics
Mendelian genetics is the study of how traits are inherited through generations, based on the principles established by Gregor Mendel. It involves understanding dominant and recessive alleles, where dominant traits mask the expression of recessive ones. This framework helps predict the phenotypic ratios of offspring from specific parental crosses.
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Descriptive Genetics
Phenotype and Genotype
The phenotype refers to the observable characteristics of an organism, such as height or fruit shape, while the genotype is the genetic makeup that determines these traits. In this context, understanding the relationship between genotype and phenotype is crucial for predicting the traits of the progeny resulting from the crosses described in the question.
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Gamete Genotypes
Punnett Square
A Punnett square is a diagram used to predict the genetic outcomes of a cross between two organisms. It allows for the visualization of how alleles from each parent combine to form the genotypes of the offspring. By filling out a Punnett square based on the parental genotypes, one can easily determine the expected proportions of different phenotypes in the progeny.
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Chi Square Analysis
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