Concept explainers
Fill in the following diagram of a cross of round-seeded and wrinkled-seeded pea plants. The round allele (R) is dominant; the wrinkled allele (r) is recessive.
To label: The given diagram that shows a cross between round-seeded and wrinkled-seeded pea plants.
Introduction: Gregor Johann Mendel who is known as the “Father of modern genetics” was the first person to conduct experiments on seven characters of pea plant. Based on these experiments, he framed three laws of inheritance, namely “Law of dominance, “Law of segregation”, and “Law of independent assortment.”
Answer to Problem 1IQ
Pictorial representation: Fig.1 represents a cross between round-seeded and wrinkled-seeded pea plants.
Fig.1: A cross between round seeded and wrinkled-seeded pea plants
Explanation of Solution
The description of cross between the round-seeded and wrinkled-seeded pea plants from parental generation till F2 generation is given below:
- The parental generation includes the phenotypes that are round seeds and wrinkled seeds and their genetic makeup includes RR and rr, respectively.
- The gametes of the round and wrinkled seeds are R and r, respectively.
- These gametes fertilize to produce only round seeds in the F1 generation. This is because their genetic makeup is Rr and the allele for round seeds R is dominant over the wrinkled seeds r.
- The F1 round-seeded plants whose genotype is Rr segregate into R and r at the time of gamete formation and fuse together to give rise to F2 generation.
- The F2 generation gives rise to plants with different genotypes that are RR, Rr, and rr giving rise to both round and wrinkled seeds.
- The plants with round and wrinkled seeds are produced in the ratio 3 rounded:1 wrinkled seed plants, whereas their genetic makeup are found in the ratio 1RR: 2Rr: 1rr.
The ratios of a cross between round versus wrinkled seeds are as follows:
Phenotypic ratio of round versus wrinkled seeds is 3:1
Genotypic ratio of RR: Rr: rr is 1:2:1.
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Chapter 14 Solutions
Study Guide for Campbell Biology
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