In a genetic study, if a trait is controlled by a single gene with two alleles, where one allele is completely dominant over the other, what is the expected genotypic ratio in the offspring of a monohybrid cross?
Practice Questions
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Q1
In a genetic study, if a trait is controlled by a single gene with two alleles, where one allele is completely dominant over the other, what is the expected genotypic ratio in the offspring of a monohybrid cross?
1:2:1
3:1
1:1
9:3:3:1
The expected genotypic ratio from a monohybrid cross is 1:2:1.
Questions & Step-by-step Solutions
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Q
Q: In a genetic study, if a trait is controlled by a single gene with two alleles, where one allele is completely dominant over the other, what is the expected genotypic ratio in the offspring of a monohybrid cross?
Solution: The expected genotypic ratio from a monohybrid cross is 1:2:1.
Steps: 8
Step 1: Understand that a monohybrid cross involves one trait controlled by one gene with two alleles.
Step 2: Identify the two alleles. Let's say 'A' is the dominant allele and 'a' is the recessive allele.
Step 3: Determine the possible genotypes of the parents. They can be homozygous dominant (AA), homozygous recessive (aa), or heterozygous (Aa).
Step 4: Perform a cross between two heterozygous parents (Aa x Aa).
Step 5: Use a Punnett square to find the possible combinations of alleles in the offspring.
Step 6: Fill in the Punnett square: the combinations will be AA, Aa, Aa, and aa.
Step 7: Count the genotypes: 1 AA, 2 Aa, and 1 aa.
Step 8: Write the genotypic ratio: 1 AA : 2 Aa : 1 aa.
