Dihybrid Crosses

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# Dihybrid Crosses - PowerPoint PPT Presentation

Dihybrid Crosses. Mendel’s Peas. In addition to Mendel’s monohybrid cross experiments, he also studied the probability of inheriting 2 separate traits Example: Seed colour and seed shape Seeds can be green or yellow; they can also be wrinkled or smooth

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### Dihybrid Crosses

Mendel’s Peas
• In addition to Mendel’s monohybrid cross experiments, he also studied the probability of inheriting 2 separate traits
• Example: Seed colour and seed shape
• Seeds can be green or yellow; they can also be wrinkled or smooth
• What’s the probability of getting green, wrinkled seeds?
Consider the following:

Yellow seeds = Y Green seeds = y

Round seeds = R Wrinkled seeds = r

If a pea plant is heterozygous for both traits, how many different sex cells can it produce?

YyRr

If 2 plants, heterozygous for both traits are crossed, what types of offspring are possible?

Does inheriting yellow seeds, change the probability of the seeds being wrinkled?
• NO! Traits are inherited independently from one another because alleles are on separate chromosomes.
• One chromosome from each homologous pair is randomly assigned to each sex cell during meiosis.
• This is known as the Law of Independent Assortment.
• It’s like flipping a coin for every trait and chance has no memory: flipping ‘heads’ the first time, does not make it more likely that you will flip ‘tails’ the next time.