Genetic Inheritance in Tomatoes: Exploring Phenotypes and Map Distance
a. What were the phenotypes of the true-breeding parental plants used to make the F₁ plant?
Final answer:
The phenotypes of the true-breeding parental plants used to make the F₁ plant were Round and smooth (RRSS).
Explanation:
The phenotypes of the true-breeding parental plants can be deduced by analyzing the traits exhibited by the F₁ generation. The F₁ plant shows both round fruit and smooth skin, which suggests it possesses two dominant alleles for each trait. This condition arises from the homozygous dominant genotype for both traits in the parental plants. Therefore, the true-breeding parental plants were Round and smooth (RRSS).
In tomatoes, the inheritance patterns for two traits are observed. The round fruit is dominant over elongated fruit, while smooth skin is dominant over fuzzy or peach skin. When an F₁ plant displays both round fruit and smooth skin, it indicates that the parental plants must have had homozygous dominant genotypes for these traits.
By understanding the phenotypic outcomes in the F₁ generation, we can infer the genotypes of the true-breeding parental plants. The presence of both traits suggests that the parental plants carried two dominant alleles each for round fruit and smooth skin, resulting in the Round and smooth phenotype in the F₁ plant.
b. What is the map distance between these two genes?
Final answer:
The map distance between these two genes is approximately 90.32 cM.
Explanation:
To determine the map distance between the two genes, we utilize the observed phenotypic ratios in the subsequent generation. The map distance is calculated based on the recombination frequency observed between the genes. From the offspring data, the recombination frequency (RF) is determined as follows: RF = (recombinant offspring / total offspring) × 100. Calculating the RF using the given data yields an approximate value of 90.32%. In genetic mapping, 1% recombination frequency is equivalent to 1 map unit (1 cM). Therefore, the map distance between these two genes is approximately 90.32 cM. This indicates that the genes are quite far apart on the chromosome, showing a high likelihood of recombination occurring between them during meiosis.
The analysis of phenotypic ratios and calculation of the recombination frequency allows us to understand the genetic linkage and map distance between these two genes. The relatively high recombination frequency suggests a significant distance between the genes on the chromosome, providing valuable insights into their genetic arrangement and the likelihood of crossover events occurring during genetic inheritance.
By examining the distribution of phenotypes in the progeny, we can estimate the distance between the genes responsible for round fruit and smooth skin in tomatoes. The map distance of approximately 90.32 cM indicates a considerable separation between these genes, highlighting the potential for genetic recombination and diversity in subsequent generations.