What is the Difference Between F1 and F2 Generation

The main difference between F1 and F2 generation is that F1 generation is the first filial generation of the offspring from the parents. But, F2 generation is the second filial generation of the offspring, generated through inbreeding of F1 individuals. Furthermore, the F1 generation is distinctly different from the parental types. In contrat, the F2 generation may exhibit some parental phenotypes. Moreover, the F1 generation is important in hybridization, obtaining the best characteristics of parents in the offspring. Meanwhile, F2 generation is important in inbreeding in order to maintain stable traits over generations. 

In brief, F1 and F2 generation are two generations of the offspring of a dihybrid cross. Here, a dihybrid cross or a two traits cross is a genetic cross done between two individuals that are identically hybrid for two traits. 

Key Areas Covered 

1. What is the F1 Generation
      – Definition, Genetics, Importance
2. What is F2 Generation
      – Definition, Genetics, Importance
3. What are the Similarities Between F1 and F2 generation
      – Outline of Common Features
4. What is the Difference Between F1 and F2 Generation
      – Comparison of Key Differences

Key Terms 

Dihybrid, F1 Generation, F2 Generation, Hybridization, Inbreeding, Outbreeding

What is the F1 Generation 

The F1 generation is the first filial generation of the dihybrid cross. Here, a dihybrid cross is a genetic cross, which focuses on the inheritance of two independent traits. Therefore, it describes the second law of Mendel; The Independent Assortment.  

Genetics 

Generally, the parents used in a dihybrid cross are identically hybrid for the two traits testing. Hence, they produce two types of gametes that are the dominant form and recessive form for both traits. Also, the F1 generation shows a single genotype, which is heterozygous for both traits. Subsequently, its phenotype shows dominant phenotypes of both traits.

Figure 1: F1 Generation

Hybridization 

Importantly, F1 generation shows increased heterozygosity, which in turn increases the vigor. Therefore, hybridization is the genetic process, which results in the F1 generation. Furthermore, hybridization is one of the two methods of selective breeding. More specifically, in hybridization, breeding occurs between two parents that are genetically dissimilar. Moreover, the parents may belong to different breeds or cultivars within the same species. Also, the resulting offspring is known as the hybrid.  

Outbreeding 

Besides, the breeding method, which involves unrelated organisms is outbreeding. As outbreeding combines the characteristics of different pure breeds, it increases the variation of a group of organisms through mating. Basically, the breeding of individuals in two populations of the same genus is an example of outbreeding. However, outbreeding makes more heterozygous allele combinations within the offspring, randomly mixing all the possible alleles found in the population. Still, outbreeding depression is the main disadvantage of outbreeding in which the production of unsuitable traits for the present habitat is produced that reduces the fitness to the environment.   

What is F2 Generation 

The F2 generation is the second filial generation of the dihybrid cross. Significantly, it is the offspring produced by crossing individuals of the F1 generation. 

Genetics 

In comparison, the F2 generation is the second filial generation of the dihybrid cross, producing through inbreeding of individuals of the F1 generation. Hence, the four types of gametes produced by the F1 generation contain all combinations of dominant and recessive forms of the two testing traits. On the other hand, F2 generation shows a phenotypic ratio of 9:3:3:1, having 9 individuals with both dominant traits, 3 individuals in two sets with one dominant and one recessive trait and one individual with both traits recessive respectively. 

Figure 2: Dihybrid Cross

Inbreeding 

Furthermore, inbreeding is the other method of selective breeding opposite to hybridization or outbreeding. Basically, it involves breeding from closely-related animals, especially over many generations. Importantly, it increases the homozygosity of the offspring. Hence, inbreeding can be used to maintain pure lines. Therefore, the main purpose of inbreeding is to maintain the desired characteristics of parents in the offspring. For example, dog breeders, horse breeders, and the breeders of exotic animals often use inbreeding to increase a desired genetic trait from the parents in the offspring. However, the negative side effects of inbreeding include the emphasizing of the undesirable characteristics of the parents, such as physical and mental abnormalities in the offspring.  

Similarities Between F1 and F2 generation 

• F1 and F2 generation are the two generations of the offspring of a dihybrid cross. 
• The parents of the dihybrid cross are identically hybrid for two traits. 
• Also, a dihybrid cross is performed to describe the inheritance of two traits. 
• In the Mendelian inheritance, a dihybrid cross describes the Second Law or the Law of Independent Assortment. 

Difference Between F1 and F2 Generation  

Definition 

F1 generation refers to the first filial generation of the offspring from the parents, while F2 generation is the second filial generation of the offspring, generated through inbreeding of F1 individuals.  

Method of Crossing 

The F1 generation is a result of outbreeding, but F2 generation is a result of inbreeding. 

Parents 

The parents of the F1 generation are two individuals that are identically hybrid for two traits, while the parents of the F2 generation are the individuals of the F1 generation. 

Genetic Similarity of Parents 

The F1 generation is a result of a cross between genetically dissimilar parents, but F2 generation is a result of a cross between genetically similar parents.  

Genetics of the Parents 

One parent of the F1 generation is homozygous dominant for both traits while the second is homozygous recessive. In contrast, the parents of the F2 generation are heterozygous for both traits. 

Gametes 

The two types of gametes that form the F1 generation are YR and yr, while the four types of gametes that form the F2 generation are YR, Yr, yR, and yr. 

Genotypic Ratio 

F1 generation shows a single genotype; RrYy, which is heterozygous for both traits. Meanwhile, F2 generation shows RRYY 1:RRYy 2:RRyy 1:RrYY 2:RrYy 4:Rryy 2:rrYY 1:rrYy 2:rryy 1  

Phenotypic Ratio 

F1 generation shows a single phenotype with dominant characteristics for both traits, while F2 generation shows a phenotypic ratio 9:3:3:1. 

The Similarity of Phenotypes to the Parents 

The F1 generation is distinctly different from the parental types, but the F2 generation may exhibit some parental phenotypes. 

Effect to the Vigor 

F1 generation has an increased vigor, while the F2 generation has a decreased vigor. 

Importance 

The F1 generation is important in hybridization, obtaining the best characteristics of parents in the offspring. Meanwhile, the F2 generation is important in inbreeding in order to maintain stable traits over generations. 

Conclusion 

The F1 generation is the first filial generation of the dihybrid cross. Basically, the parents used in a dihybrid cross are identical hybrid for two traits. Also, the genotype of the F1 generation is heterozygous for both traits. However, its phenotype shows dominant phenotypes of both traits. Therefore, F1 generation shows hybridization and its method of breeding is outbreeding. In contrast, the F2 generation is the second filial generation of the dihybrid cross, producing through interbreeding of individuals of the F1 generation. Usually, the phenotypic ratio of F2 generation is of 9:3:3:1 with more similar phenotypes to the P generation. Thereby, the F2 generation is important for the maintenance of parental traits over several generations. On that account, the main difference between F1 and F2 generation is the characteristics and importance of genotypes and phenotypes of each generation. 

References:

1. Hyatt, Donald W. “WHAT’S THE DIFFERENCE BETWEEN F1 AND F2?” JARS v59n4, Available Here.

Image Courtesy:

1. “Dihybrid Crosses” By Sonaallii – Own work (CC BY-SA 4.0) via Commons Wikimedia   
2. “Figure 12 03 02” By CNX OpenStax (CC BY 4.0) via Commons Wikimedia