What is Genotypic Ratio _ It’s Meaning and Definition Pattern of offspring distribution.
What is Genotypic Ratio _ It’s Meaning and Definition Pattern of offspring distribution.
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What is Genotypic Ratio? – Meaning, Definition & Explanation
Definition:
The genotypic ratio is the proportion of different genotypes (genetic makeup) observed in the offspring after a genetic cross. It represents the pattern of genetic distribution based on the parental alleles.
Explanation with Example
Genotype refers to the genetic composition of an organism (e.g., AA, Aa, aa).
Genotypic ratio is calculated using a Punnett Square in genetic crosses.
Example: Monohybrid Cross (Mendel’s Pea Plant – Tall vs. Short)
Parental Genotypes: TT (Tall) × tt (Short)
Punnett Square Calculation:
| T | T | |
|---|---|---|
| t | Tt | Tt |
| t | Tt | Tt |
Offspring Genotypes: 100% Tt (Heterozygous Tall)
Genotypic Ratio: 0:4:0 (TT:Tt:tt) → 0 TT, 4 Tt, 0 tt
Example: Dihybrid Cross (Two Traits – Seed Shape & Color)
Parental Genotypes: RrYy × RrYy
Punnett Square Results:
| Genotype | Count |
|---|---|
| RRYY | 1 |
| RRYy | 2 |
| RrYY | 2 |
| RrYy | 4 |
| RRYy | 2 |
| Rryy | 2 |
| rrYY | 1 |
| rrYy | 2 |
| rryy | 1 |
Genotypic Ratio: 1:2:2:4:2:2:1:2:1
Key Points About Genotypic Ratios
The ratio changes depending on dominant (capital letter) & recessive (small letter) alleles.
Typical Genotypic Ratios in Crosses:
-
Monohybrid Cross (Aa × Aa): 1:2:1 (AA:Aa:aa)
-
Dihybrid Cross (RrYy × RrYy): 1:2:2:4:2:2:1:2:1
The phenotypic ratio may be different from the genotypic ratio.
Would you like more examples or a detailed Punnett Square explanation?
