In a Mendel's dihybrid experiment, a homozygous pea plant with round yellow seeds was crossed with a homozygous plant with wrinkled green seeds. F₁ intercross produced 560 F₂ progeny. The number of F₂ progeny having both dominant traits (round and yellow) is ________
Diploid Inheritance Calculation
In Mendel's dihybrid cross, the inheritance of two different traits is studied. The initial cross is between a homozygous plant with dominant traits (Round Yellow seeds, genotype $RRYY$) and a homozygous plant with recessive traits (wrinkled green seeds, genotype $rryy$).
F₁ Generation
All F₁ offspring are heterozygous ($RrYy$) and display the dominant phenotypes (Round and Yellow).
F₂ Generation Phenotypic Ratio
When F₁ plants ($RrYy$) self-cross ($RrYy$ x $RrYy$), the F₂ generation exhibits a specific phenotypic ratio based on independent assortment:
- 9 Dominant, Dominant (Round, Yellow)
- 3 Dominant, Recessive (Round, green)
- 3 Recessive, Dominant (wrinkled, Yellow)
- 1 Recessive, Recessive (wrinkled, green)
The total ratio is $9 + 3 + 3 + 1 = 16$.
Calculating F₂ Progeny Count
The question states that the F₁ intercross produced 560 F₂ progeny. We need to find the number of progeny exhibiting both dominant traits (Round and Yellow).
The proportion of F₂ progeny with both dominant traits is 9 out of 16 ($\frac{9}{16}$).
The expected number of F₂ progeny with both dominant traits is calculated as:
$ \text{Number} = \left(\frac{9}{16}\right) \times \text{Total F₂ Progeny} $ $ \text{Number} = \left(\frac{9}{16}\right) \times 560 $ $ \text{Number} = 9 \times \left(\frac{560}{16}\right) $ $ \text{Number} = 9 \times 35 $ $ \text{Number} = 315 $Therefore, the number of F₂ progeny having both dominant traits (round and yellow) is 315.
Important Questions from Mendelian Inheritance
The allele associated with albinism in humans is recessive ($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?
- 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 ________.
A pedigree of an inheritable disease is shown below.
- In tomato plant, red (R) is dominant over yellow (r) for fruit color and purple (P) is dominant over green (p) for stem color. Fruit color and stem color assort independently. The number of progeny plants of different fruit/stem colors obtained from a mating are as follows:
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?
