CBSE Class 12 Biology Principles of Inheritance and Variation (2). CBSE issues sample papers every year for students for class 12 board exams. Students should solve the CBSE issued sample papers to understand the pattern of the question paper which will come in class 12 board exams this year. The sample papers have been provided with marking scheme. It’s always recommended to practice as many CBSE sample papers as possible before the board examinations. Sample papers should be always practiced in examination condition at home or school and the student should show the answers to teachers for checking or compare with the answers provided. Students can download the sample papers in pdf format free and score better marks in examinations. Refer to other links too for latest sample papers.
a) Is the trait recessive or dominant?
b) Is the trait sex- linked or autosomal?
c) Give the genotypes of the parents in generation I and of their third and fourth child in generation II.
2 Recently a girl baby has been reported to suffer from haemophilia. How is it possible? Explain with the help of a cross.
3 In one family each of the four children has a different blood group. Their mother is group A and the father is group B. Explain this pattern of inheritance with the help of a cross along with the genotypes.
4 Why are F2 phenotypic and genotypic ratios same in a cross between red-flowered snapdragon and white-flowered snapdragon plants. Explain with the help of a cross.
5 Workout a cross between true breeding red and white flowered dog-flower plants ( Snapdragon) up to F2 progeny. Explain the results of F1 and F2 generations.
Ques. A marriage between normal visioned man and colour blind woman will produce offspring
(a) colour blind sons and 50% carrier daughter
(b) 50% colourblind sons and 50% carrier daughter
(c) normal males and carrier daughters
(d) colour blind sons and carrier daughters.
Ques. Haemophilic man marries a normal woman. Their offspring will be
(a) all haemophilic
(b) all boys haemophilic
(c) all girls haemophilic
(d) all normal.
Ques. A woman with two genes for haemophilia and one gene for colour blindness on one of the ‘X’ chromosomes marries a normal man. How will the progeny be?
(a) 50% haemophilic colour-blind sons and 50% normal sons.
(b) 50% haemophilic daughters (carrier) and 50% colour blind daughters (carrier).
(c) All sons and daughters haemophilic and colourblind.
(d) Haemophilic and colour-blind daughters.
Ques. Mental retardation in man, associated with sex chromosomal abnormality is usually due to
(a) moderate increase in Y complement
(b) large increase in Y complement
(c) reduction in X complement
(d) increase in X complement.
Ques. Albinism is known to be due to an autosomal recessive mutation. The first child of a couple with normal skin pigmentation was an albino. What is the probability that their second child will also be an albino?
(a) 50% (b) 75%
(c) 100% (d) 25%
Ques. A person with the sex chromosomes XXY suffers from
(b) Klinefelter’s syndrome
(c) Down’s syndrome
(d) Turner’s syndrome.
Ques. In which of the following diseases, the man has an extra X-chromosome?
(a) Turner’s syndrome (b) Klinefelter’s syndrome
(c) Down’s syndrome (d) Haemophilia
Ques. A person whose father is colour blind marries a lady whose mother is daughter of a colour blind man. Their children will be
(a) all sons colour blind
(b) some sons normal and some colour blind
(c) all colour blind
(d) all daughters normal.
Ques. A genetically diseased father (male) marries with a normal female and gives birth to 3 carrier girls and 5 normal sons. It may be which type of genetic disease?
(a) Sex-influenced disease
(b) Blood group inheritance disease
(c) Sex-linked disease
(d) Sex-recessive disease
Ques. An abnormal human male phenotype involving an extra X-chromosome (XXY) is a case of
(a) Edward’s syndrome
(b) Klinefelter’s syndrome
(d) Down’s syndrome.
Ques. The genes, which remain confined to differential region of Y-chromosome, are
(a) autosomal genes (b) holandric genes
(c) completely sex-linked genes
(d) mutant genes.
Ques. Albinism is a congenital disorder resulting from the lack of which enzyme?
(a) Tyrosinase (b) Xanthine oxidase
(c) Catalase (d) Fructokinase
Ques. The colour blindness is more likely to occur in males than in females because
(a) the Y-chromosome of males have the genes for distinguishing colours
(b) genes for characters are located on the sexchromosomes
(c) the trait is dominant in males and recessive in females
(d) none of these.
Ques. Of both normal parents, the chances of a male child becoming colour blind are
(b) possible only when all the four grand parents had normal vision
(c) possible only when father’s mother was colour blind
(d) possible only when mother’s father was colour blind.
Ques. Of a normal couple, half the sons are haemophiliac while half the daughters are carriers. The gene is located on
(a) X-chromosome of father
(b) Y-chromosome of father
(c) one X-chromosome of mother
(d) both the X-chromosomes of mother.
Ques. A colour blind mother and normal father would have
(a) colour blind sons and normal/carrier daughters
(b) colour blind sons and daughters
(c) all colour blind
(d) all normal.
Ques. Down’s syndrome is due to
(a) crossing over
(c) sex-linked inheritance
(d) non-disjunction of chromosomes.
Ques. In human beings 45 chromosomes/single X/XO abnormality causes
(a) Down’s syndrome
(b) Kinefelter’s syndrome
(c) Turner’s syndrome
(d) Edward’s syndrome.
Ques. A colour blind girl is rare because she will be born only when
(a) her mother and maternal grand father were colour blind
(b) her father and maternal grand father were colour blind
(c) her mother is colour blind and father has normal vision
(d) parents have normal vision but grand parents were colour blind.
Ques. In Down’s syndrome of a male child, the sex complement is
(a) XO (b) XY
(c) XX (d) XXY.
Ques. Haemophilia is more common in males because it is a
(a) recessive character carried by Y-chromosome
(b) dominant character carried by Y-chromosome
(c) dominant trait carried by X-chromosome
(d) recessive trait carried by X-chromosome.
Ques. Which one is a hereditary disease?
(a) Cataract (b) Leprosy
(c) Blindness (d) Phenylketonuria
Ques. Both husband and wife have normal vision though their fathers were colour blind. The probability of their daughter becoming colour blind is
(a) 0% (b) 25%
(c) 50% (d) 75%.
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