Question

In haploids the monohybrid ratio is
A. 3:1
B. 1:1
C. 1:2:1
D. 15:1

Answer 1

Monohybrid ratio may be defined as the phenotypic ratio of different types of individuals in the F2 generation of a monohybrid cross. Phenotypic ratio is the relative number of offspring manifesting a particular trait or combination of traits.

Complete step by step answer:
- Monohybrid ratio is a cross between two parents that possess a pair of contrasting characters called monohybrid cross. For example a cross of tall (T) and dwarf (t) pea plant is a monohybrid cross. Monohybrid cross determines the allele combinations of offspring of only one particular gene.
- The dihybrid cross is defined as inheritance of two pairs of contrasting characters at same time by two parents. For example cross of two tea plants one with yellow and round seeds while the other with green and wrinkled seeds.
Monohybrid cross can be calculated by punnett square.
- Punnett square is a diagram that is used to predict the genotypes of particular crosses.
- Mono means one. So this cross means the examination of a single trait.
Let’s take an example of eye color.
B-brown eyes and b- green eyes
Now if both the parents have brown eyes and have genotype Bb, the gametes will be B and b. so below is the punnett square.
In the given Punnett square - M means maternal and P means paternal.
So as mentioned in the Punnett square the probability of an individual's offspring having genotype BB is 25%, Bb is 50% and bb is 25%.

| P
---|---
| B| b
M| B| BB| Bb
| b| Bb| bb

3 offspring have brown eyes and one offspring have Green eyes.
The ratio of phenotypes for monohybrid cross is 3:1.
The monohybrid ratio is 3:1. The correct answer is option A.

Note:
1: Haploid, the cells that consist of a single set of chromosomes. In humans, gametes are haploid cells containing 23 chromosomes.
2: The monohybrid cross is a cross between two organisms with different variations at one chromosome of interest.