Distinguish Between Parental and Recombinant Phenotypes

Main Difference – Parental vs Recombinant Phenotypes

Parental and recombinant phenotypes are the two types of phenotypes that arise during sexual reproduction of organisms. The main difference between prenatal and recombinant phenotypes is that parental phenotypes are the phenotypes of the offspring that resemble the phenotypes of the parents whereas recombinant phenotypes are the phenotypes of the offspring that differ from the phenotypes of the parents. Thus, it is the resemblance between the offspring and parent phenotypes that help to distinguish between parental and recombinant phenotypes. The organisms that pass down certain traits over generations is known as true-breeding organisms or a purebred. The recombinant phenotypes arise due to the crossing-over during meiosis I.

Key Areas Covered

1. What are Parental Phenotypes
     – Definition, Inheritance, Examples
2. What are Recombinant Phenotypes
     – Definition, Inheritance, Examples
3. What are the Similarities Between Parental and Recombinant Phenotypes
     – Outline of Common Features
4. How to Distinguish Between Parental and Recombinant Phenotypes
     – Comparison of Key Differences

Key Terms: Allele, Crossing Over, Genotype, Mendelian Traits, Parental Phenotypes, Recombinant Phenotypes, Recombination

What are Parental Phenotypes

Parental phenotypes are the phenotypes of the offspring that matches one of the true-breeding parental (P generation) phenotypes. Gregor Mendel first described the inheritance of the phenotypes from parents to the offspring with his famous experiment with pea plants. The phenotype of a particular organism is determined by its genotype, the presenting alleles of the organism. As described by Mendel, two alleles are involved in the determination of a particular phenotype in diploid organisms. The two alleles can be either homozygous or heterozygous. In a heterozygous allele combination, only one allele is expressed over the other, determining the phenotype of the organism. The expressed allele is referred to as the dominant allele while the hidden allele is referred to as the recessive allele. Both dominant alleles, as well as recessive alleles, can generate parental alleles. Generally, dominant alleles are expressed in the first generation (F₁ generation) of the offspring while the recessive alleles are expressed in the second generation (F₂ generation). The expression of the dominant and recessive alleles as parent phenotypes is shown in figure 1.

Figure 1: The Expression of Parental Phenotypes

Generally, parental phenotypes are controlled by a single locus. They are known as Mendelian traits. Some Mendelian traits in humans are wet or dry earwax, Albinism, blood type, cystic fibrosis, Sickle-cell disease, hereditary breast-ovarian cancer syndrome, etc.

What are Recombinant Phenotypes

Recombinant phenotypes are the phenotypes of the offspring that differ from that of the true-breeding P generation parents. Mendel observes that some combinations of traits in the offspring differ from either parent. These phenotypes are identified as nonparental or recombinant phenotypes. Recombinant phenotypes arise due to the crossing-over of genes during meiosis. This crossing over occurs between two genes located on the same chromosome. The amount of crossing over depends on the distance between the two genes on the chromosome. If the two genes are far apart, the frequency of recombination of genes is 50%. Genes closely located on the chromosome exhibit a few crossing-over events. Gametes with recombined chromosomes are known as recombinant gametes while parent gametes carry non-recombinant chromosomes. Recombinant gametes produce recombinant phenotypes that differ from the phenotypes of the offspring. Recombinant phenotypes bring variations to a particular population. The expression of parental and recombinant phenotypes in a dihybrid cross is shown in figure 2. The short tail (S) and the Brown coat color (B) are the dominant alleles.

Figure 2: The Expression of the Parental and Recombinant Phenotypes in a Dihybrid Cross

Here, the phenotypes of the parents are short tail: white coat color (SSbb) and long tail: brown coat color (ssBB). In the F₁ generation, the phenotype is short tail: brown coat color. The recombination is involved in the production of gametes in the F₂ generation. Hence, four combinations of the gametes can be considered as recombinant gametes. Recombinant gametes produce two recombinant phenotypes in the second generation such as short tail: brown coat color, long tail: white coat color.

Similarities Between Parental and Recombinant Phenotypes

• Parental and recombinant phenotypes are the two types of phenotypes that can be arisen during the sexual reproduction.
• Both parental and recombinant phenotypes obey the Mendelian Inheritance.

How to Distinguish Between Parental and Recombinant Phenotypes

Definition

Parental Phenotypes: Parental phenotypes refer to the phenotypes of the offspring that resemble one of the true-breeding parental (P generation) phenotypes.

Recombinant Phenotypes: Recombinant phenotypes refer to the phenotypes of the offspring that differ from that of the true-breeding P generation parents.

Significance

Parental Phenotypes: Parental phenotypes are the phenotypes of the offspring that resemble the P generation.

Recombinant Phenotypes: Recombinant phenotypes are the phenotypes of the offspring that differ from the phenotypes of the P generation.

Occurrence

Parental Phenotypes: Parental phenotypes are the traits controlled by a single locus.  

Recombinant Phenotypes: Recombinant phenotypes are the traits controlled by two loci.

Role

Parental Phenotypes: The parental phenotypes are important in maintaining the desired traits over generations.

Recombinant Phenotypes: The recombinant phenotypes introduce phenotypic variations in the offspring.

Conclusion

Parental and recombinant phenotypes are the two types of phenotypes that can arise during sexual reproduction. Parental phenotypes are the phenotypes of the offspring that resemble the phenotypes of the P generation. Recombinant phenotypes are the phenotypes of the offspring that differ from the phenotypes of the P generation. Therefore, the main difference between parental and recombinant phenotypes is the resemblance of the phenotypes of the offspring to the P generation.

Reference:

1. “Inheritance of Traits by Offspring Follows Predictable Rules.” Nature News, Nature Publishing Group, Available here.
2. “Recombination and Estimating the Distance Between Genes.” Genetic Linkage, Available here.

Image Courtesy:

1. “Mendelian inheritance” By Benutzer:Magnus Manske http://de.wikipedia.org/wiki/Datei:Mendelian_inheritance_3_1.png (Public Domain) via Commons Wikimedia
2. “Dihybrid cross” By Tocharianne (PNG version), WhiteTimberwolf (SVG version) – PNG version (Public Domain) via Commons Wikimedia