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Dihybrid Crosses and Pedigrees. Dihybrid Crosses. Monohybrid punnett squares only look at one trait at a time (just flower color, just height…)
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Dihybrid Crosses • Monohybrid punnett squares only look at one trait at a time (just flower color, just height…) • Law of Independent Assortment – most traits (found on different chromosomes) are inherited separately. Ex - Height does not have an impact on flower color. (See exception) • If you want to know the likelihood of inheriting two separate traits together (e.g. What are the chances of creating a plant that is tall AND has purple flowers?) you must use a dihybrid cross.
How to do a dihybrid cross • Step One – establish the genotypes of the parents. • Cross two pea plants that are heterozygous for both tall height and yellow flower traits. • Parent Genotypes: __________________ • Step Two - Use the FOIL method to show the possible allele combinations each parent could pass on to their offspring. • FOIL = First alleles in a pair, Outside alleles in a pair, Inside alleles in a pair, Last alleles in a pair • Allele possibilities: _________________ • Step Three - Fill in the square to show the possible genotypes of the offspring. Keep the like letters together!
Dihybrid cross ____ : ____ : ____ : ____
Dihybrid cross ____ : ____ : ____ : ____
What is a pedigree? • Pedigrees are used to track how a trait transfers through multiple generations.
Example • Add numbers to the pedigree. • How many generations? • How many kids did the parents in generation I have? • Were any of these kids affected? If so, which one(s)? • How many kids did the parents in generation II have? • Were any of these kids affected? If so, which one(s)?
