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
- Genetic Cloning
  9m
- Methods for Analyzing DNA
  9m
19. Cancer Genetics29m
- Overview of Cancer
  21m
- Cancer Mutations
  7m
20. Quantitative Genetics1h 26m
21. Population Genetics50m
- Hardy Weinberg
  19m
- Allelic Frequency Changes
  31m
22. Evolutionary Genetics29m

4. Genetic Mapping and Linkage

Trihybrid Cross

Genetics

4. Genetic Mapping and Linkage

Trihybrid Cross

Previous problemNext problem

2:36 minutes

Problem 12

Textbook Question

Three gene pairs located on separate autosomes determine flower color and shape as well as plant height. The first pair exhibits incomplete dominance, where the color can be red, pink (the heterozygote), or white. The second pair leads to personate (dominant) or peloric (recessive) flower shape, while the third gene pair produces either the dominant tall trait or the recessive dwarf trait. Homozygous plants that are red, personate, and tall are crossed to those that are white, peloric, and dwarf. Determine the F₁ genotype(s) and phenotype(s). If the F₁ plants are interbred, what proportion of the offspring will exhibit the same phenotype as the F₁ plants?

Verified step by step guidance

Step 1: Identify the genotypes of the parental plants. The first gene pair exhibits incomplete dominance for flower color, so the homozygous red parent is represented as 'RR' and the homozygous white parent as 'rr'. The second gene pair determines flower shape, where personate (dominant) is 'PP' and peloric (recessive) is 'pp'. The third gene pair determines plant height, where tall (dominant) is 'TT' and dwarf (recessive) is 'tt'. Thus, the genotypes of the parents are 'RRPP TT' (red, personate, tall) and 'rrpp tt' (white, peloric, dwarf).

Step 2: Determine the F₁ genotypes by performing a cross between the parental genotypes. Since the first gene pair exhibits incomplete dominance, the F₁ offspring for flower color will all be heterozygous 'Rr', resulting in pink flowers. For the second and third gene pairs, the F₁ offspring will all be heterozygous 'Pp' (personate) and 'Tt' (tall), as these traits follow simple Mendelian dominance. Therefore, the F₁ genotype is 'RrPpTt'.

Step 3: Determine the F₁ phenotype. The F₁ plants will exhibit the dominant traits for flower shape and height (personate and tall, respectively) and the intermediate phenotype for flower color (pink) due to incomplete dominance. Thus, the F₁ phenotype is pink, personate, and tall.

Step 4: Predict the F₂ generation by interbreeding the F₁ plants ('RrPpTt' × 'RrPpTt'). Use a Punnett square or the forked-line method to calculate the genotypic and phenotypic ratios for each gene pair independently. For the first gene pair (incomplete dominance), the phenotypic ratio will be 1 red: 2 pink: 1 white. For the second and third gene pairs (Mendelian dominance), the phenotypic ratios will be 3 personate: 1 peloric and 3 tall: 1 dwarf, respectively.

Step 5: Calculate the proportion of F₂ offspring with the same phenotype as the F₁ plants (pink, personate, tall). Multiply the probabilities of each phenotype occurring independently: (2/4 for pink) × (3/4 for personate) × (3/4 for tall). This will give the proportion of F₂ offspring that exhibit the same phenotype as the F₁ plants.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above

Video duration:

Play a video:

Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Incomplete Dominance

Incomplete dominance is a genetic phenomenon where the heterozygous phenotype is an intermediate blend of the two homozygous phenotypes. For example, in this case, crossing a red flower (homozygous) with a white flower (homozygous) results in pink flowers (heterozygous), illustrating how neither allele is completely dominant over the other.

Gene Interaction and Epistasis

Gene interaction refers to the way different gene pairs influence each other's expression, which can affect phenotypes. In this scenario, the flower shape and height traits are determined by separate gene pairs, but their interactions can lead to various combinations in the offspring, showcasing the complexity of inheritance patterns.

Punnett Square and Mendelian Ratios

A Punnett square is a tool used to predict the genotypes and phenotypes of offspring from genetic crosses. By setting up a Punnett square for the F₁ generation, one can determine the expected ratios of phenotypes in the offspring, which helps in understanding the inheritance patterns and calculating the proportion of offspring that exhibit specific traits.

Watch next

Master Trihybrid Cross with a bite sized video explanation from Kylia

Start learning

Related Videos

Related Practice

Multiple Choice

The following table shows data from a cross examining three genes (a, b, and c). Calculate the recombination frequency for A and C

The following table shows data from a cross examining three genes (a, b, and c). Determine the order of genes

Determine whether the statements below are true or false. If a statement is false, provide the correct information or revise the statement to make it correct.

The outcome of a trihybrid cross is predicted by the law of segregation.

433

views

Textbook Question

Determine whether the statements below are true or false. If a statement is false, provide the correct information or revise the statement to make it correct.

The progeny of a trihybrid cross are expected to have one of 27 different genotypes.

350

views

Textbook Question

Researchers cross a corn plant that is pure-breeding for the dominant traits colored aleurone (C1), full kernel (Sh), and waxy endosperm (Wx) to a pure-breeding plant with the recessive traits colorless aleurone (c1), shrunken kernel (sh), and starchy (wx). The resulting F₁ plants were crossed to pure-breeding colorless, shrunken, starchy plants. Counting the kernels from about 30 ears of corn yields the following data.

What is the interference value for this data set?

419

views

Textbook Question

Calculate the recombination frequencies between the gene pairs.

562

views

Textbook Question

Flower color may be red, white, or pink, and flower shape may be personate or peloric. For the following crosses, determine the P₁ and F₁ genotypes:

452

views

Textbook Question

In a diploid plant species, an F₁ with the genotype Gg Ll Tt is test-crossed to a pure-breeding recessive plant with the genotype gg ll tt. The offspring genotypes are as follows:

Calculate the recombination frequency between each pair of genes.

727

views

Show more practices

Download the Mobile app

Privacy

Do not sell my personal information

Accessibility

Patent notice

Sitemap