With the help of a checkerboard show the phenotypic ratio of offspring produced in F2 generation as a result of a cross between a pure black coloured and rough-haired guinea pig and a pure white and smooth-haired guinea pig. “Father plays the main role in the determination of sex of the offspring” – justify the statement with the help of a checkerboard. [3+2=5]
OR
Write three reasons behind Mendel’s success. Establish a relationship between phenotype and genotype with the help of proper examples. [3+2=5]
Pure Black and Rough: BBRR
Pure White and smooth: bbrr
F1 generation: BbRr (Hybrid Black and Rough)
Phenotypic ratio = 9 : 3 : 3 : 1
The father contributes an X chromosome to all of his offspring, while the mother contributes either an X or a Y chromosome. This means that the father’s X chromosome will always be present in his offspring, while the mother’s X chromosome may or may not be present.
Therefore, the father has a greater influence on the sex of the offspring than the mother.
Or
Three reasons behind Mendel’s success:
- Mendel used purebred pea plants which had consistent traits, allowing him to clearly observe inheritance patterns.
- He conducted large-scale hybridization experiments, which provided statistically significant data.
- Mendel applied mathematical and statistical methods to analyze the inheritance patterns, making his conclusions reliable.
Relationship between phenotype and genotype:
Phenotype is the observable physical appearance of an organism, while genotype is the genetic makeup that determines the phenotype. For example, a pea plant with the genotype “YY” will have yellow seeds, indicating that yellow color is the phenotype, whereas the presence of “Y” and “y” alleles (genotype Yy) results in the same yellow phenotype due to dominance. Conversely, “yy” results in green seeds, showing how genotype influences phenotype.
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