Main Difference – Monohybrid Cross vs Dihybrid Cross
Monohybrid cross and dihybrid cross are two genetic crossing methods that are used to study the inheritance of allele pairs. These are useful in understanding the inheritance of traits from one generation to another. Monohybrid cross is a genetic cross that involves a single pair of genes that is responsible for one trait. In a monohybrid cross, parents differ by a single trait. Dihybrid cross is a genetic cross that involves two pairs of genes which are responsible for two traits. In a dihybrid cross, parents have two different independent traits. The key difference between monohybrid cross and dihybrid cross is that in a monohybrid cross, inheritance of one trait (e.g.: height) is studied while in a dihybrid cross, inheritance of two independent traits (e.g.: flower colour, stem length) is studied.
Key Areas Covered
1. What is a Monohybrid Cross
– Definition, Traits, Process
2. What is a Dihybrid Cross
– Definition, Traits, Process
3. What are the Similarities Between Monohybrid Cross and Dihybrid Cross
– Outline of Common Features
4. What is the Difference Between Monohybrid Cross and Dihybrid Cross
– Comparison of Key Differences
Key Terms: Allele, Dihybrid Cross, Genetic Cross, Inheritance, Monohybrid Cross, Single Trait Cross, Traits, Two Traits Cross
What is a Monohybrid Cross?
A monohybrid cross is a genetic cross which occurs between two individuals, focusing on the inheritance of one trait at one time. Monohybrid cross is also known as single trait cross. Two homozygous parents are selected for this cross and studies are carried out about only one trait (for example, flower color), ignoring all other traits; thus, only a single gene pair is involved in this test method. This method is a crossbreeding of two true breeding parental lines. The following image explains the process of monohybrid crossing.
Figure 01: Monohybrid Cross
One parent is homozygous for the dominant allele, and the other parent is homozygous for the recessive allele. The offspring is predicted and assessed for one trait inheritance in monohybrid cross. Therefore, the phenotypic ratio of the resulting offspring is 3:1 in monohybrid cross.
What is a Dihybrid Cross?
A dihybrid cross is a genetic cross that occurs between two individual, focusing on the inheritance of two independent traits at one time. Dihybrid cross is also known as two traits cross. The two parents considered for this cross have two independent traits (for example, pod color and pod shape in pea plants). Thus, a dihybrid cross involves two pairs of genes. The following figure explains the process of dihybrid crossing.
Figure 02: Dihybrid Cross
In a dihybrid cross, traits are considered as not linked, and they have an equal probability of sharing up in offspring. Each pair of alleles segregates independently of the gametes. Offspring is predicted and assessed for two trait inheritance. The phenotypic ratio of the offspring generation is 9:3:3:1 in a dihybrid cross.
Similarities Between Monohybrid Cross and Dihybrid Cross
- Genes are involved in both monohybrid cross and dihybrid cross.
- Both crosses study how characteristics are transmitted to the offspring.
- In both crosses, gene alleles are not considered as linked.
Difference Between Monohybrid Cross and Dihybrid Cross
Definition
Monohybrid Cross: A monohybrid cross is a genetic cross between homozygous individuals with different alleles for a single gene locus of interest.
Dihybrid Cross: A dihybrid cross is a genetic cross between individuals with different alleles for two gene loci of interest.
Number of Traits Considered
Monohybrid Cross: In a monohybrid cross, one character is considered and studied.
Dihybrid Cross: In a dihybrid cross, two independent characters are considered and studied.
Number of Gene Pairs
Monohybrid Cross: In a monohybrid cross, a single pair of genes is involved.
Dihybrid Cross: In a dihybrid cross, two pairs of genes are involved.
Phenotypic Ratio of the Offspring
Monohybrid Cross: The predicted phenotypic ratio of a monohybrid cross is 3:1.
Dihybrid Cross: The predicted phenotypic ratio of dihybrid cross is 9:3:3:31.
Importance
Monohybrid Cross: Monohybrid cross is important for determining the dominance relationship of the alleles.
Dihybrid Cross: Dihybrid cross is important for assessing the independent assortment of alleles.
Conclusion
The main difference between monohybrid and dihybrid cross is the number of traits being studies in offspring. In a monohybrid cross, inheritance of a single trait is predicted. Parents of monohybrid crosses are different in one trait and are homozygous for the trait. In dihybrid crosses, inheritance of two traits is predicted. Parents of the dihybrid cross differ in two traits. If the alleles or the genes are not linked, the resulting phenotypic ratio of a monohybrid cross is 3:1 while in a dihybrid cross, it is 9:3:3:1.
Reference:
1. “Monohybrid cross.” Wikipedia, Wikimedia Foundation, 8 Jan. 2018, Available here.
2. “Dihybrid cross.” Wikipedia, Wikimedia Foundation, 22 Oct. 2017, Available here.
3. Bailey, Regina. “Monohybrid Cross: A Breeding Experiment.” ThoughtCo, Available here.
Image Courtesy:
1. “Figure 12 02 02” By CNX OpenStax – (CC BY 4.0) via Commons Wikimedia
2. “Figure 12 03 02” By CNX OpenStax – (CC BY 4.0) via Commons Wikimedia
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