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Question
Given below is a schematic representation of the inheritance of the shape of the seeds of garden peas. Answer the questions that follow:
- Which is the dominant and recessive allele of the trait?
- What does the ratio 3 : 1 in the F2 generation represent?
- State Mendel's Law of Dominance.
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Solution
- The dominant allele is R (for round seeds), while the recessive allele is r (for wrinkled seeds). This is obvious because only round seeds develop in F1, whereas the wrinkled characteristic is entirely concealed.
- 3:1 indicates that three of the four seeds are spherical and one is wrinkled. That is, 75% of the F2 progeny have round seeds (the dominant characteristic), but only 25% have wrinkled seeds (the recessive trait).
- Mendel's law of dominance states that if an organism has two distinct alleles for a trait, the dominant allele will be expressed, hiding the recessive allele. This means that only the dominant allele determines the organism's phenotype.
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RELATED QUESTIONS
Differentiate between the following:
Dominance and Recessive
Differentiate between the following:
Homozygous and Heterozygous
How would you find out whether a given tall garden pea plant is homozygous or heterzygous? Substantiate your answer with the help fo Punnett squares.
A certain couple got four daughters in a sequence and no son. Does it mean that the husband does not produce Y-chromosome bearing sperms? Explain. What is the chance of this couple having a daughter?
Name the conditions when both the alleles are identical?
Pure-bred tall pea plants are first crossed with pure-bred dwarf pea plants. The pea plants obtained in the F1 generation are then selfed to produce F2 generation of pea plants.
What is the ratio of tall plants to dwarf plants in the F2 generation?
A Monohybrid cross is ______
Cross between hybrid and recessive parent:
In a monohybrid cross of plants with red and white flowered plants, Mendel got only red-flowered plants. On self-pollinating these F1 plants got both red and white flowered plants in 3:1 ratio. Explain the basis of using RR and rr symbols to represent the genotype of plants of parental generation.
In a plant tallness is dominant over dwarfness and red flower is dominant over white. Starting with the parents work out a dihybrid cross. What is standard dihybrid ratio? Do you think the values would deviate if the two genes in question are interacting with each other?
