In tomatoes, the allele T for tall plant height is dominant to dwarf allele t, the P allele for smooth skin is dominant to the p allele for peach fuzz skin, and the allele R for round fruit is dominant to the recessive r allele for oblong fruit. The genes controlling these traits are linked on chromosome 1 in the tomato genome, and the genes are arranged in the order and with the recombination frequencies shown.

What are the genotype and phenotype of the F₁ progeny of this cross?

Verified step by step guidance

1. Step 1: Understand the genetic traits and alleles involved. In this problem, there are three traits: plant height (T/t), skin texture (P/p), and fruit shape (R/r). Each trait has a dominant allele (T, P, R) and a recessive allele (t, p, r). The genes are linked on chromosome 1, meaning they are inherited together unless recombination occurs.
2. Step 2: Analyze the parental genotypes. Determine the genotypes of the parents involved in the cross. For example, one parent might be homozygous dominant for all traits (TTPPRR), while the other parent might be homozygous recessive (ttpprr). This information is crucial for predicting the F₁ progeny.
3. Step 3: Predict the F₁ genotype. Since the genes are linked, the F₁ progeny will inherit one set of alleles from each parent. If no recombination occurs, the F₁ genotype will be heterozygous for all traits (TtPpRr). Consider recombination frequencies to account for possible genetic variation.
4. Step 4: Determine the F₁ phenotype. The phenotype is determined by the dominant alleles. In this case, the F₁ progeny will express the dominant traits: tall plant height, smooth skin, and round fruit. This is because the dominant alleles (T, P, R) mask the effects of the recessive alleles (t, p, r).
5. Step 5: Consider recombination frequencies. If recombination occurs between the linked genes, it may result in new combinations of alleles. Use the recombination frequencies provided to calculate the likelihood of different genotypes and phenotypes in the F₁ progeny.

Key Concepts

Dominant and Recessive Alleles

In genetics, alleles are different forms of a gene that can exist at a specific locus on a chromosome. Dominant alleles, represented by uppercase letters (e.g., T, P, R), mask the expression of recessive alleles, represented by lowercase letters (e.g., t, p, r). In the context of the question, the dominant alleles determine the observable traits (phenotypes) in the offspring, while the recessive alleles only manifest when two copies are present.

Genotype and Phenotype

The genotype refers to the genetic makeup of an organism, specifically the alleles it possesses for a particular trait. The phenotype, on the other hand, is the observable expression of those traits, influenced by the genotype and environmental factors. In the given question, understanding the genotype of the F₁ progeny will help predict their phenotype based on the dominance of the alleles involved.

Linked Genes and Recombination

Linked genes are genes located close together on the same chromosome, which tend to be inherited together during meiosis. The recombination frequency indicates how often these genes can be separated during crossing over in meiosis. In the context of the question, knowing that the traits are linked on chromosome 1 helps in predicting the inheritance patterns of the alleles in the F₁ progeny, as linked genes can affect the ratios of genotypes and phenotypes observed.