Agricultural Science (AS)·Crop science · NSSCAS 3.1b
Plant reproduction & genetics: dihybrid crosses, meiosis & mitosis
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A seed company sells a maize that is both round and yellow, and farmers pay well for it. But when a farmer keeps that seed and replants it, the next crop is a mix — some round, some wrinkled, some yellow, some green. Why? In this lesson we follow two traits at once through a dihybrid cross, work out the famous 9:3:3:1 ratio on the board, meet the F1 hybrid, and see how meiosis, mitosis and cell enlargement build a whole plant.
What you'll learn in this lesson
By the end you should be able to (NSSCAS Agricultural Science (AS) 3.1b):
- Predict the outcome of a dihybrid cross and derive the 9:3:3:1 phenotypic ratio using a Punnett square
- State the rule of independent assortment and use it to work out the gametes a dihybrid parent can make
- Explain the benefits and the main drawback of using F1 hybrid seed in crop production
- Explain how meiosis produces genetically varied haploid gametes and how mitosis produces identical cells
- Describe how cell division and cell enlargement together lead to the growth of a plant
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Miss Elina and Mike talk through the whole topic — with the figure and working drawn live.