EasyBiologyHigh School (11–12)Heredity and Evolution › Principles of Inheritance and VariationNumericalAPA-LevelIB
A pea plant has the genotype AaBbCc. The three genes lie on three different chromosomes…
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A pea plant has the genotype AaBbCc. The three genes lie on three different chromosomes. The plant pollinates itself.
- How many kinds of gamete does the plant make?
- How many kinds of genotype can the F2 have?
- How many boxes does the Punnett square of this cross have?
Need a reminder? The key ideaShow
Genes on different chromosomes assort independently, so you can multiply the chances of the separate genes. RrYy × RrYy gives 9 round yellow : 3 round green : 3 wrinkled yellow : 1 wrinkled green. A plant heterozygous for genes makes kinds of gamete, and its F2 has genotypes.
The worked solution
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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. AaBbCc, three independent genes.
Plan. Multiply the choices for the three genes.
Step 1. (a) Each gene gives two alleles: kinds of gamete.
Step 2. (b) Each gene alone gives three genotypes: .
Step 3. (c) Each parent makes kinds of gamete, so the square has boxes.
Answer: kinds of gamete; genotypes; boxes.
Check. The F2 has boxes, but only different genotypes. Several boxes share a genotype.
Watch out. Do not add the numbers of alleles. The choices multiply.
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