Red fruit, purple stem - 145
Red fruit, green stem – 184
Yellow fruit, purple stem - 66
Yellow fruit, green stem - 47
What are the genotypes of the parent plants in this mating?
Dihybrid Cross Analysis: Parent Genotype Determination
Phenotypic Ratio Calculation
First, calculate the observed phenotypic ratios for each trait separately from the progeny data:
- Fruit Color:
- Red Phenotype Count: 145 + 184 = 329
- Yellow Phenotype Count: 66 + 47 = 113
- Observed Ratio (Red:Yellow) = 329 : 113. This simplifies to approximately 3:1.
- Stem Color:
- Purple Phenotype Count: 145 + 66 = 211
- Green Phenotype Count: 184 + 47 = 231
- Observed Ratio (Purple:Green) = 211 : 231. This simplifies to approximately 1:1.
Deducing Parental Genotypes
Interpret these ratios to determine the likely genotypes of the parent plants:
- A 3:1 phenotypic ratio typically results from a monohybrid cross between two heterozygotes. For fruit color, this implies the parents had genotypes Rr x Rr.
- A 1:1 phenotypic ratio typically results from a cross between a heterozygote and a homozygous recessive parent. For stem color, this implies the genotypes were Pp x pp.
Synthesizing Parent Genotypes
Given that the genes assort independently, combine the deduced genotypes for each parent:
- Parent 1: Must be heterozygous for fruit color (Rr) and heterozygous for stem color (Pp). Its genotype is RrPp.
- Parent 2: Must be heterozygous for fruit color (Rr) and homozygous recessive for stem color (pp). Its genotype is Rrpp.
Therefore, the parental genotypes are RrPp x Rrpp.
Important Questions from Mendelian Inheritance
- Mendel's 'law of segregation' applies to the segregation of __________ during gamete formation.
- Fabry disease in humans is a X-linked disease. The probability (in percentage) for a phenotypically normal father and a carrier mother to have a son with Fabry disease is ________.
The allele associated with albinism in humans is recessive ($c$). The probability that an albino male ($cc$) and a carrier female ($Cc$) will have an offspring with normal skin pigmentation is _________.
(Round off to one decimal place)
- The blood group of the mother is A⁺ and that of the father is AB⁺. Which of the following statements is/are correct?
- Assuming independent assortment and no recombination, the number of different combinations of maternal and paternal chromosomes in gametes of an organism with a diploid number of 12 is ________.
