Biology Forum › Genetics › Cross problem
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- March 22, 2009 at 6:52 pm #11104
sims262ParticipantCan anyone help me with this problem?
A female of genotype AaBBCCDD is mated to a male of genotype aaBBCcdd. What are the expected genotypic proportions of the offspring (assuming no linkage)?
I’m guessing there is some sort of equation or relationship to the number of heterozygous alleles at each loci, but I can’t figure it out. Thanks!
- March 23, 2009 at 1:15 am #89823viennaParticipant
Parents: Female x Male
Genotype: AaBBCCDD x aaBBCcdd
Gametes formed: A, a, B, C, D a, B, C, c, D
Hence combining the different types of gametes one can find the genotypes that can be produced by the given combination of parental genotypes.]
Genotypes of offsprings: AaBBCCDD, aaBBCCDD, AaBBCcDD and aaBBCcDD.
This can be formulated as follows:
Number of genotypes formed = 2^Number of characteristics that are heterozygous.
In this case only 2 characterisics are heterozygous hence the types of gametes formed will be 2 x 2 = 4. - March 23, 2009 at 4:34 pm #89835sims262Participant
That’s all well and good, but doesn’t really answer the question. I still need to know in what proportions those possible phenotypes occur. 😕
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