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NCERT Class 12 Biology Chapters
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1.
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Two statements are given one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
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.
(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, but Reason (R) is not the correct explanation of the Assertion (A).
(c) Assertion (A) is true, but Reason (R) is false.
(d) Assertion (A) is false, but Reason (R) is true.
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2.
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Three genes R, S and T are located on the same chromosome. If the recombination percentage between R and S is 20%, R and T is 35% and S and T is 15% respectively, can you predict the correct order of these genes on the chromosome? Which of the following shows the correct sequence of the genes on the chromosome?
(a) R T S (b) R S T (c) S R T (d) S T R
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3.
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Two statements are given one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
Assertion (A): In humans the genotype with all the dominant alleles (AABBCC) will have the darkest skin colour.
Reason (R): In a polygenic trait, phenotype reflects the contribution of each allele.
(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, but Reason (R) is not the correct explanation of the Assertion (A).
(c) Assertion (A) is true, but Reason (R) is false.
(d) Assertion (A) is false, but Reason (R) is true.
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4.
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Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
Assertion (A): Birds like pigeon have heterogametic females whereas the males are homogametic.
Reason (R): In pigeons, females have Z and W sex chromosomes whereas males have ZZ sex chromosomes.
(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, but Reason (R) is not the correct explanation of the Assertion (A).
(c) Assertion (A) is true, but Reason (R) is false.
(d) Assertion (A) is false, but Reason (R) is true.
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5.
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Choose the set of sex determining chromosomes that indicates the correct sex of the respective organism.
(a) Homozygous sex chromosomes (ZZ) determine female sex in birds
(b) XO type of sex chromosomes determine male sex in grasshoppers
(c) XXY condition in humans, as found in Turner Syndrome, determines male sex
(d) Homozygous sex chromosomes (XX) produce male sex in Drosophila
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1.
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(i) A true breeding tall pea plant with round seeds is crossed with a recessive dwarf pea plant having wrinkled seeds. Work out the cross up to F2 generation giving the phenotypic ratios of F1 and F2 generation respectively.
(ii) State the Mendelian principle that can be derived only with the help of such a cross.
(CBSE 2023, 5M)
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2.
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A homozygous tall pea plant with green seeds is crossed with a homozygous dwarf pea plant with yellow seeds.
(i) Write the possible phenotype and genotype of F1 generation.
(ii) State the laws of Mendel that are proved true by the F1 generation.
(iii) Mention the F2 phenotypic ratio along with their possible phenotypes.
(iv) Write the genotypes of the male and female gametes produced by F1 progeny.
(CBSE 2023, 5M)
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3.
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You are given a tall pea plant with green seeds. The genotype of this plant is unknown. You are allowed to do only ‘selfing’ of these plants to find out the genotype of the given plant.
Work out all possible crosses and show how you would determine the genotype of the given plant.
(CBSE 2023, 5M)
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4.
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Describe the dihybrid cross upto F2 generation as conducted by Gregor Mendel using pure lines of Garden Pea for characters seed shape and seed colour.
(CBSE 2023, 5M)
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5.
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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.
(CBSE 2023, 2M)
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Chapter Name
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Sub Topics
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Principles of Inheritance and Variation
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4.1 Introduction
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4.2 Mendel’s Laws of Inheritance
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4.3 Deviations from Mendel’s Laws
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4.4 Chromosomal Theory of Inheritance
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4.5 Linkage and Crossing Over
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4.6 Mutations and Genetic Variation
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4.7 Sex Determination
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4.8 Genetic Disorders: Chromosomal and Mendelian
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