Genetics of Flower Color Inheritance: Exploring a Monohybrid Cross

[Foghorn]

Homework Statement

A cross between two plants that both have green flowers produces 80 offspring plants, of which 36 have green flowers, 23 have black flowers, and 21 have blue flowers. Color variation is due to inheritance at one locus. What is the genotype associated with each flower color?

How can the inheritance of the flower color be described?

Homework Equations

Law of Independent Assortment
Law of Segregation

The Attempt at a Solution

36/80 green
23/80 black
21/80 blue

such numbers yield a ratio close to 1:2:1, equivalent to a monohybrid cross.

Gg x Gg

1 GG
2 Gg
1 gg

This seems to indicate either codominance or incomplete dominance. However, in this case, the hybrids are neither a blend of their parents nor do they exhibit traits from both parents, so I'm left a little confused.

Do I need to somehow incorporate mutations or wild type into this?

 

[nobahar]

Hello!
From Scitable, Genetic Dominance: Genotype-Phenotype Relationships, under the overdominance section:

"In some instances, offspring can demonstrate a phenotype that is outside the range defined by both parents."

It's difficult to think of a scenario that is plausible for the phenotpye of heterozygotes. Perhaps one does not dtermine colour without the presence of the other allele. Homozygous individuals in this case may have a 'default' colour due to the presence of a molecule, A. One allele may convert A to B, and the other allele B to C. Without the allele converting A to B, the allele for B to C will not perform its function, the flower will then have the default colour in individuals homozygous for this allele. Homozygous individuals for the the other allele, will convert A to B, producing a certain colour; and heterozygous individuals will convert A to B and B to C, producing yet another colour (in this case, green). This seems plausible, but I'm not sure if it is what you are looking for.

 

[Blueshift5]

I would first clarify the terminology used in the question. In genetics, a monohybrid cross refers to the crossing of two individuals that differ in only one trait or characteristic, in this case, flower color. The question also mentions "inheritance at one locus," which means that the gene responsible for flower color is located on a specific region of the chromosome.

Based on the information provided, it is likely that the gene for flower color exhibits incomplete dominance. In this scenario, the heterozygous offspring (Gg) would have an intermediate phenotype, resulting in the observed ratio of 1:2:1 for green, black, and blue flowers. Codominance, on the other hand, would result in both traits being fully expressed in the heterozygous offspring, leading to a 1:2:1 ratio of green, black, and blue flowers.

In terms of genotype, the green flowers would have the genotype GG, the black flowers would have the genotype gg, and the blue flowers would have the genotype Gg. This can also be represented using Punnett squares, where the dominant allele (G) is represented by a capital letter and the recessive allele (g) is represented by a lowercase letter.

As for the inheritance of flower color, it can be described as a simple Mendelian inheritance, following the laws of independent assortment and segregation. The law of independent assortment states that during gamete formation, the alleles for different traits are sorted into the gametes independently of each other. The law of segregation states that during gamete formation, the two alleles for a trait separate from each other, so each gamete carries only one allele for that trait.

In conclusion, the inheritance of flower color in this case can be described as a monohybrid cross with incomplete dominance, where the gene for flower color is located on a specific locus and follows the laws of independent assortment and segregation.