PRINCIPLES OF INHERITANCE AND VARIATION

DOWNLAOD THE ASSIGNMENT HERE:

https://www.sciencearena.in/p/education-resources.html

BIOLOGY TOPICS:

EUGLENA:

https://www.sciencearena.in/2025/05/euglena.html

MONOCYSTIS:

https://www.sciencearena.in/2025/05/monocystis.html

PARAMECIUM:

https://www.sciencearena.in/2025/05/paramecium.html

ATS COACHING CLASSES

BIOLOGY (XII)

PRINCIPLES OF INHERITANCE AND VARIATION

MULTIPLE CHOICE QUESTIONS (MCQs)

1	A snapdragon plants bearing pink colour flowers is crossed with a snapdragon plant bearing white colour flowers. Their F₁progeny will show (a) 25% Red : 50% Pink : 25%White (b) 50% Red : 50% White : (c) 50% Pink : 50% White (d) 25% Pink : 50% Red : 25%White.	1
2	The number of different types of gametes that would develop in an organism with genotype AABBCCDd. (a) 1 (b) 2 (c) 3 (d) 4	1
3	How many types of gametes can be produced in a diploid organism which is heterozygous for 3 loci ? (a) 4 (b) 8 (c) 16 (d) 32	1
4	The chromosomal theory of inheritance was put forth by (a) Gregor Mendel and Tschermark (b) Walter Sutton and Theodore Boveri (c) Thomas Hunt Morgan and Alfred Sturtevant (d) De Vries and Correns.	1
5	Select the pair-that is not correct. (a) Pleiotropy : Sickle Cell anaemia (b) Linkage : Drosophila (c) Incomplete dominance : Antirrhinum (d) Co-dominance : ABO blood group	1
6	In which of the following chromosomal disorder do the individuals have shorts stature, small head furrowed tongue and partially open (a) Turner’ s syndrome (b) Down’s syndrome (c) Klinefelter’ s syndrome (d) Edwards’ syndrome	1
7	The cause for Klinefelter’ s syndrome in human is because of (a) an extra copy of autosome (b) an extra copy of X chromosome (c) absence of one X chromosome (d) absence of one Y chromosome.	1
8	The autosomal disorder/disease in humans in (a) colour blindness (b) thalassemia (c) haemophilia (d) Turner’ s syndrome.	1
9	How many types of gametes would be produced if the genotype of a parent is AaBB? (a) 1 (b) 2 (c) 3 (d) 4	1
10	Morgan hybridized Drosophila white eyed and yellow bodied female with red eyed and brown bodied male (wild type) and intercrossed their F₁ progeny. He observed that the two genes (a) did not segregate independent of each other (b) may be located on two different chromosomes (c) segregated independently of each other (d) showed very high percentage of recombinants	1

ASSERTION AND REASON QUESTIONS

(a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).

(b) Both Assertion (A) and Reason (R) are true and Reason (R) is not the correct explanation of the Assertion (A).

(c) Assertion (A) is true, and Reason (R) is false.

(d) Assertion (A) is false, and Reason (R) True.

11	Assertion (A): In a monohybrid cross between tall plants and dwarf plants, the F₂ generation showed tall and dwarf plants in the ratio of 3: 1. Reason (R): There is no blending of traits/characters in the F₂ generation.	1
12	Assertion (A): In thalassemia, an abnormal myoglobin chain is synthesised due to a gene defect. Reason (R): α-thalassemia is controlled by genes HBA1 and HBA2 on chromosome 16.	1
13	Assertion (A): When white eyed, yellow bodied Drosophila females were hybridized with red eyed, brown-bodied males; and F₁progeny was intercrossed, F₂ ratio deviated from 9:3:3:1. Reason (R): When two genes in a dihybrid are on the same chromosome, the proportion of parental gene combinations is much higher than the non-parental type.	1
14	Assertion (A): When the two genes in a dihybrid cross are situated on the same chromosome, the proportion of parental gene combinations is much higher than non-parental type. Reason (R): Higher parental gene combinations can be attributed to crossing over between two genes.	1

VERY SHORT ANSWER QUESTIONS

15	Two children one with blood group 'AB' and other with blood group 'O' are born to parents where the father has blood group 'A' and the mother has blood group 'B'. Work out a cross to show how is it possible?	2
16	By using Punnett square depict the genotypes and phenotypes of test crosses (where green pod colour (G) is dominant over yellow pod colour (g) in garden pea with unknown genotype.	2
17	State and explain the law of segregation as proposed by Mendel in a monohybrid cross.	2
18	Differentiate between 'ZZ' and 'XY' type of sex-determination mechanisms.	2
19	Differentiate between male and female heterogamety.	2
20	Although haemophilia and sickle cell anaemia are two blood related Mendelian disorders, yet, they differ in their pattern of inheritance. State any two differences.	2

SHORT ANSWER TYPE QUESTIONS

21	The F₂ progeny of a monohybrid cross showed phenotypic and genotypic ratio as 1:2:1, unlike that of Mendel's monohybrid F₂ ratio. With the help of a suitable example, work out a cross and explain how it is possible.	3
22	Differentiate between dominance, incomplete dominance and co-dominance with the help of a suitable example of each.	3
23	"Human blood group (ABO group) inheritance is a good example of multiple allelism and co-dominance." Justify the statement.	3
24	Compare in any three ways the chromosomal theory of inheritance as proposed by Sutton and Boveri with that of experimental results on pea plant presented by Mendel.	3
25	Explain the mechanism of haplo-diploid pattern of sex determination with the help of a suitable example. Why is this pattern so called?	3
26	During a medical investigation, an infant was found to possess an extra chromosome 21. Describe the symptoms the child is likely to develop later in the life.	3
27	Differentiate between the pattern of inheritance in humans of the blood diseases haemophilia and thalassemia.	3
28	In a family, the father, the daughter and the son are colour-blind, whereas the mother has normal vision. Do you think the son and the daughter have inherited the disease from their father? Work out a cross to justify your answer.	3

LONG ANSWER TYPE QUESTIONS

29	(a) State and explain the law of dominance as proposed by Mendel. (b) How would phenotypes of monohybrid F₁ and F2 progeny showing incomplete dominance in snapdragon and co-dominance in human blood group be different from Mendelian monohybrid F₁ and F₂ progeny? Explain.	5
30	Mendel crossed a homozygous pea plant having yellow and round seeds with another pea plant bearing green and wrinkled seeds. He found that in some of the F₂ population new combination of parental characters were observed. How will you explain the appearance of a new combination of parental characters in F₂-off springs? Support your answer with the help of Punnett square.	5
31	(a) Write the scientific name of the organism Thomas Hunt Morgan and his colleagues worked with for their experiments. Explain the correlation between linkage and recombination with respect to genes as studied by them. (b) How did Sturtevant explain gene mapping while working with Morgan?	5
32	(a) How are Mendelian inheritance, polygenic inheritance and pleiotropy different from each other? (b) Explain polygenic inheritance pattern with the help of a suitable example	5
33	(a) Why are colour-blindness and thalassemia categorized as Mendelian disorders? Write the symptoms of these diseases seen in people suffering from them. (b) Explain polygenic inheritance pattern with the help of a suitable example	5
34	(a) Why are colour-blindness and thalassemia categorized as Mendelian disorders? Write the symptoms of these diseases seen in people suffering from them. (b) About 8% of human male population suffers from colour-blindness whereas only about 0.4% of human female population suffers from this disease. Write an explanation to show how it is possible.	5
35	How do "pleiotropy", "incomplete dominance", "co-dominance" and "polygenic inheritance" deviate from the observation made by Mendel? Explain with the help of one example for each.	5

CASE BASED STUDY QUESTIONS

36	Read the passage carefully and answer the following questions given below. Gregor Mendel conducted experiments on pea plants and formulated the laws of inheritance. He selected traits such as flower colour, seed shape, and pod colour. In one of his experiments, he crossed a pure tall plant (TT) with a pure dwarf plant (tt). 1. What would be the genotype and phenotype of the F1 generation? 2. What will be the phenotypic ratio in the F2 generation if two F1 plants are crossed? 3. Which law of Mendel is demonstrated in the F1 generation? 4. Explain the genotypic ratio obtained in the F2 generation. 5. Name two reasons why Mendel chose pea plants for his experiments.	4
37	Read the passage carefully and answer the following questions given below. A woman with blood group A marries a man with blood group B. Their child has blood group O. 1. What are the possible genotypes of the parents? 2. Explain how the child inherited blood group O. 3. Which type of inheritance pattern does this case represent? 4. Can they have another child with blood group AB? Explain. 5. What is the importance of codominance in this case?	4
38	Read the passage carefully and answer the following questions given below. A couple has two daughters. The husband wants a son and blames the wife for only giving birth to daughters. 1. Explain scientifically who determines the sex of the child in humans. 2. What is the chromosomal combination in females and males? 3. Why is it incorrect to blame the mother for the sex of the child? 4. What mechanism of sex determination is followed in humans? 5. How is this different from sex determination in birds?	4
39	Read the passage carefully and answer the following questions given below. A red-flowered Snapdragon is crossed with a white-flowered Snapdragon. All the F1 plants have pink flowers. 1. What is the phenomenon observed in the F1 generation? 2. What will be the phenotypic and genotypic ratio in the F2 generation? 3. How does incomplete dominance differ from complete dominance? 4. Write the genotype of red, white, and pink flowered plants. 5. Give one more example of a trait showing incomplete dominance.	4
40	Read the passage carefully and answer the following questions given below. In pea plants, round seed shape (R) is dominant over wrinkled (r), and yellow cotyledon (Y) is dominant over green (y). A plant heterozygous for both traits is self-crossed. 1. What is the phenotypic ratio of the offspring? 2. List all the possible genotypes produced in the F2 generation. 3. How does this cross demonstrate Mendel’s law of independent assortment? 4. What would be the phenotype of a plant with genotype RrYy? 5. What is the probability of getting wrinkled green seeds in the offspring?	4