A farmer saves the seed of a hybrid crop, which is heterozygous for one gene, and sows it…
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A farmer saves the seed of a hybrid crop, which is heterozygous for one gene, and sows it. The plants self-pollinate, and the share of heterozygous plants halves in each generation. Another farmer has a hybrid that makes apomictic seed.
- What per cent of the plants are heterozygous after generations from fertilised seed?
- What per cent are heterozygous after generations?
- What per cent of the plants from apomictic seed are heterozygous after generations?
Need a reminder? The key ideaShow
The ovary becomes the fruit, and its wall becomes the pericarp. A false fruit includes the thalamus. A parthenocarpic fruit forms without fertilisation. Apomixis makes seeds without fertilisation. In polyembryony, one seed has more than one embryo. A hybrid that is heterozygous for one gene gives heterozygous plants after generations of self-pollination.
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. The share halves in each generation. Apomictic seed keeps the hybrid.
Plan. The share after generations is per cent.
Step 1. Three generations. .
Step 2. Five generations. .
Step 3. Apomictic seed. The seed is made without fertilisation, so every plant stays heterozygous: .
Answer: ; ; .
Check. , then after two more halvings.
Watch out. This model follows one gene. A real hybrid differs at many genes.
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