What is the expected ratio of phenotypes in a cross between two purebred parents with contrasting traits? (2019)
Practice Questions
1 question
Q1
What is the expected ratio of phenotypes in a cross between two purebred parents with contrasting traits? (2019)
1:1
3:1
9:3:3:1
1:2:1
The expected ratio of phenotypes in a cross between two purebred parents with contrasting traits is 1:1 in the F1 generation when they are crossed with each other.
Questions & Step-by-step Solutions
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Q
Q: What is the expected ratio of phenotypes in a cross between two purebred parents with contrasting traits? (2019)
Solution: The expected ratio of phenotypes in a cross between two purebred parents with contrasting traits is 1:1 in the F1 generation when they are crossed with each other.
Steps: 7
Step 1: Understand what purebred parents are. Purebred parents have two identical alleles for a trait (e.g., AA or aa).
Step 2: Identify the contrasting traits. For example, one parent might have a dominant trait (A) and the other a recessive trait (a).
Step 3: Cross the two purebred parents. This means you combine their alleles (e.g., AA x aa).
Step 4: Determine the genotype of the offspring (F1 generation). All offspring will have the genotype Aa, which shows the dominant trait.
Step 5: If you cross two F1 offspring (Aa x Aa), you can find the expected phenotype ratio in the next generation (F2).
Step 6: The expected phenotype ratio in the F2 generation will be 3:1 (3 showing the dominant trait and 1 showing the recessive trait).
Step 7: However, if you only consider the F1 generation from the original cross, the expected phenotype ratio is 1:1 when they are crossed with each other.
