Mapping our Genes. Gregor Johann Mendel observed that organisms inherit traits through discrete units of inheritance which are now called genes.

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1 13. C h a p t e r at G l a n c e Heredity is defined as the transmission of traits, physical or mental, from parents to offspring. Gregor Johann Mendel observed that organisms inherit traits through discrete units of inheritance which are now called genes. From his experiments on pea plants, Mendel established the laws of inheritance. Monohybrid cross is a breeding experiment between parental generation organisms that differ in one trait. E.g., Red White flowered pea plants (RR rr). Monohybrid cross produced F 1 generation in which all plants were phenotypically red flowered and genotypically hybrid. F 1 generation plants were allowed to self pollinate to produce F 2 generation. The phenotypic ratio of F 2 generation was 3 red : 1 white and the genotypic ratio was 1RR : 2Rr : 1rr. Dihybrid cross is a breeding experiment between parental generation organisms that differ in two traits. E.g., Round yellow seeds wrinkled green seeds of pea plants. (RRYY rryy) F 2 generation of dihybrid cross gave rise to phenotypic ratio 9 : 3 : 3 : 1 and genotypic ratio 1 : 2 : 2 : 4 : 2 : 2 : 1 : 1 : 1. Variations are created and are passed on from one generation to another and get accumulated in the individuals of the forthcoming generations. This leads to evolution. Darwin's theory of evolution is based on variation in species. He explained evolution with the help of his theory of natural selection. Diversity of the organisms and their features like homologous organs, embryos and fossils provide evidences in support of organic evolution. Lamarck proposed the theory of inheritance of acquired characters to explain evolution which was not widely accepted.

2 SCIENCE & TECHNOLOGY - S.S.C. 143 MULTIPLE CHOICE QUESTIONS (MCQ's) (Each question carries one mark) MCQ's BASED ON CHAPTER Moderate Level 1. Crosses of pea plants involving one pair of contrasting characters or traits are termed as : a test cross b monohybrid cross c trihybrid cross d dihybrid cross 2. The external appearance of an organism is its : a phenotype b phenotypic ratio c genotype d genotypic ratio 3. One of the two contrasting characters of a single trait which is not exhibited in the next generation is called : a homozygous b heterozygous c dominant d recessive 4. Self-crossing of F 1 hybrids results into : a P 1 generation b P 2 generation c F 2 generation d F 1 generation 5. Transmission of traits from parents to offsprings is called : a evolution b heredity c natural selection d DNA copying 6. Dominant genes are represented by : a capital letters b small letters c words d capital and small letters 7. Gregor Mendel conducted his experiments on heredity using : a potato plants b papaya plants c pea plants d tomato plants 8. According to theory of evolution of life, life was first originated in : a soil b water c air d rock 9. The progressive development of animals and plants from ancestors of different forms and functions is called : a organic evolution b synthetic evolution c heredity d natural selection 10. The theory of evolution of species by natural selection was given by : a Gregor Mendel b Darwin c Lamarck d Watson and Crick 11. The organs which have same fundamental structures but perform different functions are termed as : a homozygous b homologous c analogous d heterozygous 12. The organs which are fundamentally unlike but perform similar functions are termed as : a homologous b homozygous c analogous d heterozygous Elementary Level 1. Asexual reproduction produces identical offsprings with : a minor differences c no differences b major differences d minor similarities

3 144 Unique MCQ's 2. Mendel's experiments were based on the visible contrasting characters of : a pisum fulvum b pisum arvense c pisum sativum d pisum abyssinicum 3. Organisms inherit traits through discrete units are called : a gametes b cells c genes d chromosomes 4. The scientist who put forward the most popular model of DNA is : a Gregor Mendel b Watson & Crick c Charles Darwin d Jean-Baptiste Lamarck 5. When two parents having contrasting characters are crossed, the hybrid offsprings produced are referred to as : a F 1 generation b F 2 generation c P 1 generation d P 2 generation 6. The phenotypic ratio 9 : 3 : 3 : 1 is obtained in Mendel's : a monohybrid cross b dihybrid cross c trihybrid cross d test cross 7. A cross between pure tall plant and pure short plant produced all tall plants because : a shortness is the inherited trait b shortness is the dominant trait c tallness is the recessive trait d tallness is the dominant trait 8. According to palaeontological evidence reptiles are evolved from : a amphibians b birds c arthropods d mammals 9. The study of fossils is called : a anatomy b physiology c archaeology d palaeontology 10. Transfer of genetic materials takes place in : a vegetative propagation b binary fission c sexual reproduction d asexual reproduction Complex Level 1. Which of the following represents pure tall trait? a Tt b tt c TT d tt 2. Which of the following represents heterozygous? a RR b rr c TT d Tt 3. The phenotypic ratio of F 2 generation of Mendel's dihybrid cross is : a 9 : 3 : 3 : 1 b 1 : 2 : 2 : 4 : 2 : 1 c 3 : 1 d 1 : 2 : 1 4. The sex of a child is determined by : a the chromosome inherited from father c b the chromosome inherited from mother the chromosome inherited from father and mother d the chromosome inherited from ancestors 5. Which of the following is not analogous organs? a tail fin of lobster and flukes of whale b wings of fly and wings of bird c eyes of arthropods and vertebrates d forelimbs of man and bat 6. Which of the following is not a vestigial structure in man? a tail bone b vermiform appendix c heart muscles d wisdom teeth

4 SCIENCE & TECHNOLOGY - S.S.C Which of the following is not a 'connecting link'? a peripatus b earthworm c lung fish d duck-billed platypus 8. The scales of an ovulate pine cone and carpels of a flower are examples of : a vestigial organs b homologous organs c analogous organ d connecting links Mysterious Level 1. Haploid sex cells are called : a gametes b genes c chromosomes d traits 2. Sex of a child is decided by : a environmental factors b male gamete c female gamete d ovum 3. Pure red-flowered and white-flowered pea plants are crossed. The ratio of pure red-flowered plants to pure white-flowered plants in F 2 generation will be : a 1 : 3 b 3 : 1 c 1 : 1 d 1 : 2 : 1 4. A zygote which has 'Y' chromosome from father develops into : a a baby boy b a baby girl c either boy or girl d a blue baby 5. The number of sex chromosomes in a human zygote is : a 3 b 1 c 2 d 4 6. Which of the following is an incorrect statement? a in human females two similar chromosomes are present b human females are heterozygous c in human males two dissimilar sex chromosomes are present d in humans out of 23 pairs of chromosomes, one pair is sex chromosomes Answers MCQ's BASED ON CHAPTER Moderate Level Elementary Level Complex Level 1 - b 2 - a 3 - d 4 - c 5 - b 6 - a 7 - c 8 - b 9 - a 10 - b 11 - a 12 - c 1 - a 2 - c 3 - c 4 - b 5 - a 6 - b 7 - d 8 - a 9 - c 10 - c 1 - c 2 - d 3 - a 4 - a 5 - d 6 - c 7 - b 8 - b Mysterious Level 1 - a 2 - b 3 - c 4 - a 5 - c 6 - b

5 146 Unique MCQ's NO. NAME OF THE EXPERIMENTS 1. To find the ph of : (A) Dilute HCl (B) Dilute NaOH solution (C) Dilute acetic acid solution (D) Lemon juice (E) Water (F) Dilute sodium bicarbonate solution by using ph paper/ universal indicator. 2. To study the properties of acids and bases (HCl and NaOH) by their reaction with (A) Litmus solution (Blue/Red) (B) Zinc metal (C) Solid sodium carbonate. 3. To determine the focal length of - a) Concave mirror b) Convex lens by obtaining image of a distinct object. 4. To trace the path of a ray of light passing through a rectangular glass slab for different angles of incidence. Measure the angle of incidence, angle of refraction, angle of emergence and interpret the results. 5. To study the dependence of current (I) on the potential difference (V) across a resistor and determine its resistance. 6. To determine the equivalent resistance of two resistors when connected in series. 7. To determine the equivalent resistance of two resistors when connected in parallel. 8. To prepare a temporary mount of leaf peel to show stomata. 9. To show experimentally that light is necessary for photosynthesis. 10. To show experimentally that carbon dioxide is given out during respiration. 11. To study (A) binary fission in Amoeba and (B) budding in Hydra with the help of prepared slides. 12. To determine the percentage of water absorbed by raisins. 13. To perform and observe the following reactions and classify them into; (A) Combination Reaction (B) Decomposition Reaction (C) Displacement Reaction (D) Double Displacement Reaction i) Action of water on quick lime ii) Action of heat on ferrous sulphate crystals iii) iv) Action of iron nails kept in copper sulphate solution Reaction between sodium sulphate and barium chloride solution. 14. To observe the action of Zn, Fe, Cu and Al metals on aqueous solutions of salts (A) ZnSO 4 (B) FeSO 4 (C) CuSO 4 (D) Al 2 (SO 4 ) To study the properties of acetic acid (Ethanoic acid) : (A) odour (B) solubility in water (C) effect on litmus (D) reaction with sodium bicarbo nate.