Study the given table and answer the following questions: [Parents: A pea plant with red flowers was crossed with a pea plant with white flowers. | F_1: 30 seeds were sown and all bore plants with red flowers. | F_2: 44 seeds were sown, 33 plants bore red flowers and 11 plants bore white flowers.] (a) Depict the information given in the table in the form of a cross. (b) Deduce the F_2 phenotypic ratio / F_2 ratio showing external look as well as genotypic/genetic makeup, ratio.
Mendel's monohybrid cross
High importanceUsually 3 marks a paper · mostly case-based questions and MCQs · asked in 4 of the last papers
Notes are being written
The board questions below are real and complete — they come from the CBSE papers themselves. The written notes for this topic are still being prepared.
Board questions on this topic
9 from the CBSE papers we hold — the exact wording the board used.
Assertion (A): A human child bears all the basic features of human beings. Reason (R): It looks exactly like its parents, showing very little variations. Select the correct answer:
- (a) Both A and R are true and R is the correct explanation of A.
- (b) Both A and R are true, but R is not the correct explanation of A.
- (c) A is true, but R is false.
- (d) A is false, but R is true.
Mendel worked out the rules of heredity on garden pea using visible contrasting characters, making crosses with one or two pairs of contrasting characters.
When Mendel crossed pea plants with pure tall and pure short characteristics to produce F_1 progeny, which two observations were made by him in F_1 plants?
Mendel's experiments on inheritance in garden pea.
Justify the statement: "It is possible that a trait is inherited but may not be expressed."
Chromosomes: (i) carry hereditary information from parents to the next generation. (ii) are thread like structures located inside the nucleus of an animal cell. (iii) always exist in pairs in human reproductive cells. (iv) are involved in the process of cell division. The correct statements are:
- (a) (i) and (ii)
- (b) (iii) and (iv)
- (c) (i), (ii) and (iv)
- (d) (i) and (iv)
The statement that correctly describes the characteristic(s) of a gene is:
- (a) In individuals of a given species, a specific gene is located on a particular chromosome.
- (b) A gene is not the information source for making proteins in the cell.
- (c) Each chromosome has only one gene located all along its length.
- (d) All the inherited traits in human beings are not controlled by genes.
To trace inheritance of traits Mendel crossed pea plants with contrasting characters; crossing round-yellow seed plants with wrinkled-green seed plants gave no wrinkled-green seeds in F_1, and self-pollinating F_1 gave F_2 with different combinations of seed shape and colour.
Write any two pairs of contrasting characteristics of pea plant used by Mendel other than those mentioned above.
monohybrid cross - internal choice for sub-part (c).
Given below is a cross between a pure violet flowered pea plant (V) and a pure white flowered pea plant (v). Diagrammatically explain what type of progeny is obtained in F_1 generation and F_2 generation: Pure violet flowered plant (VV) x Pure white flowered plant (vv).
What is variation? List two main reasons that may lead to variation in a population.