Given below is a schematic representation of the inheritance of the shape of seeds of garden pea. Answer the questions that follow:
(a) Which is the dominant and recessive allele of the trait?
(b) What does the ratio 3 : 1 in the F₂ generation represent?
(c) State Mendel’s Law of Dominance.
(a) The allele for smooth seeds is dominant over the allele for wrinkled seeds, which is recessive.
(b) The ratio 3 : 1 represents the phenotypic ratio in the F₂ generation. Approximately three individuals show the dominant phenotype for every one individual showing the recessive phenotype.
(c) Out of a pair of contrasting characters present together, only one is able to express itself while the other remains suppressed. The one that expresses itself is the dominant character and the one that remains unexpressed is the recessive character.
More ICSE Moderate level questions
Which of the following sets shows examples of genetic disorders? P. Colour blindness and Malaria Q. Albinism and Cholera R. Haemophilia and Colour blindness S. Haemophilia and Albinism (a) P and Q (b) R and S (c) P and R (d) Q and S
A family has a history of colour blindness. During genetic testing, it was found that the mother is a carrier of colour blindness (XCX) and the father has normal vision (XY). What is the probability of their sons being colour-blind? (a) 25% (b) 50% (c) 75% (d) 0%
State Mendel's 'Law of Segregation'.
Ajay and Vijay are siblings. Ajay can roll his tongue while Vijay cannot. What is the genotype of their parents? (a) Both the parents are homozygous dominant. (b) Both the parents are homozygous recessive. (c) One parent is homozygous dominant, and the other is homozygous recessive. (d) Both the parents are heterozygous dominant.
A pure breeding red flower variety of pea plant (RR) is crossed with a pure breeding white flower variety of pea plant (rr). Draw a Punnett square to find out the Phenotypic and Genotypic ratios of the progeny belonging to the F2 generation.
A zygote which has an Y chromosome inherited from the father will develop into: (a) It will depend on the chromosome inherited from the mother (b) Girl (c) Either boy or girl (d) Boy
A farmer cultivates a unique species of tomato plants. The two traits selected for breeding were: Colour of the fruits and height of the plants. The farmer initially crosses a homozygous tall plant bearing red fruits (TTRR) with a dwarf plant bearing yellow fruits (ttrr) and the genotype of all the offsprings of the F1 generation was TtRr. Next, he crosses two F1 generation plants (TtRr). (a) Explain the phenotype of the offsprings of the F1 generation obtained from the initial cross. (b) Mention the phenotypic ratio of the F2 generation offsprings. (c) State Mendel's Law of Independent Assortment.
A sequence of DNA has 300 nitrogenous base pairs, of which 75 are Guanine. What is the number of Thymine in this sequence? (a) 150 (b) 100 (c) 50 (d) 75
Name the following: (i) The organelle that forms the aster during cell division. (ii) A genetic disorder in which the blood does not clot. (iii) The permanent stoppage of menstruation in human females around the age of 45 years. (iv) The openings on the barks of trees through which transpiration occurs. (v) A gaseous plant hormone which promotes ripening of fruits.
Four friends P, Q, R and S were discussing the examples of genetic disorders. The examples they quoted were as follows: P. Colour blindness and Malaria Q. Albinism and Cholera R. Haemophilia and Colour blindness S. Haemophilia and Albinism Who gave the correct examples? (a) P and Q (b) R and S (c) P and R (d) Q and S
The sex chromosome in a human ovum is: (a) X chromosome (b) Y chromosome (c) Both X and Y chromosomes (d) Either X or Y chromosome
Define the term Allele.
