Formatting page ...
UNIVERSAL EDUCATION ICSE GRADE X SUBJECT: BIOLOGY _____________________________________________________________________________ Genetics SECTION A TYPE QUESTIONS 1. Name the following. 1. The physical expression of gene in an individual. Phenotype 2. Father of genetics Gregor Johann Mendel 3. The branch of science which deals with the heredity. Genetics 4. The chromosome responsible for sex determination Sex chromosome 5. A hereditary disease in which blood does not clot. Haemophilia 6. The unit of heredity. Genes 7. Number of pairs of autosomes in humans. 22 pairs 8. The condition in which both the alleles are identical. Homozygous 9. The chemical substance which constitutes genes. DNA 10. The sex chromosome of male. X and Y 11. The allele which expresses itself on the other. Dominant 12. One genetic disease. Haemophilia 13. The genetic makeup of an organism. Genotype 14. A cross between one pair of contrasting characters. Monohybrid cross 15. Two sex linked inherited disease. Haemophilia and color blindness 16. The organism on which Mendel had worked. Pisum sativum 17. The condition in which both the alleles are identical. Homozygous 18. The type of gene which in the presence of a contrasting allele is not expressed Recessive gene 19. The pair of chromosome carrying dissimilar alleles for a particular character. Hetrozygous 20. Group of population which are genetically identical. Clone 21. The generation produced by crossing of two homozygous parents. F1 generation 22. Chromosomes are most condensed at which of the cell division. Metaphase 23. The numbers of pairs of chromosome in man and drosophila. 23; 4 24. The term used for departure from a complete similarity between individuals of the same species. Variation 25. The fundamental unit of heredity. Gene 2. Explain the terms. 1. Allele: Allele is the alternative form of the gene occupying the same position on a homologous chromosome and affecting the same characteristic but in two alternative ways. 2. Monohybrid cross: A cross between two pure breeding varieties of organism taking the alternative traits of one single character. 3. Gene: Genes are the basic unit of heredity and are part of chromosomes which determine the hereditary characteristics. 4. Phenotype: The observable character which is genetically controlled. 5. Mutation: It is a sudden change in one or more genes or in the number or in the structure of chromosome. 6. Homologous chromosome: A pair of corresponding chromosome of the same size and shape, one from each parent. 7. Heredity: The term heredity may be defined as transmission of genetically based characteristics from parent to offspring. 8. Genome: It is the full complement of the DNA including all genes and the intergenic regions. 9. Sex linked inheritance: It is the appearance of the trait which is due to the presence of an allele exclusively either on the x chromosome or on the Y chromosome. 10. Haemophilia: Haemophilia is a genetic disorder in which the sufferers are at the risk of bleeding to death because the blood fails to clot in them. 11. Dihybrid cross: A cross between two parents taking into consideration alternative traits of two different characters. 3. Mendel s law. 1. Law of independent assortment when there are two pairs of contrasting characters, the distribution of the members of one pair into the gamete is independent of the distribution of the other pair. 2. Law of segregation(law of purity of gametes) Two members of a pair of factors separate during the formation of gametes. 3. Law of dominance out of a pair of contrasting character present together, only one is able to express itself while the other remains suppressed. 4. Differentiate between the following on the basis of what is given in the bracket. 1. Monohybrid and dihybrid cross. [phenotypic ratio of f2 generation] Monohybrid cross Dihybrid cross It gives a phenotypic ratio of 3:1 in F2 It gives a phenotypic generation 9:3:3:1in F2 generation ratio of 2. Genotype and phenotype. [definition] Genotype Phenotype The set of genes present in the cells of The observable characteristic which the organism. is genetically controlled. 3. Pure and hybrid strains. [ definition] Pure strains The self pollinated progeny of homozygous plant is a pure strain. hybrid strains a The offspring of a genetically dissimilar parent is a hybrid strain. 4. Autosomes and sex chromosomes.[determination of sex] Autosomes sex chromosomes They do not participate in sex They determine the sex of an determination. It is of one type. individual. They are of two types X and Y. 5. Homozygous and heterozygous. Homozygous It contains similar kind of allele and forms only one type of gamete. It is either dominant or recessive. Heterozygous. It contains dissimilar alleles and forms two types of gametes. It has both dominant and recessive alleles. 5. Select the correct answer out of the four available choices given under each question. 1. If a tall plant is crossed with a dwarf plant, this type of cross is called: Dihybrid Reciprocal Monohybrid Trihybrid Ans: Monohybrid 2. Which of the following pair represents a pair of contrasting characters or factors? Allele Homozygous Phenotype heterozygous Ans: Heterozygous. 3. RR (red) is crossed with rr (white). All the Rr offspring are pink. This is an indication that R gene is: Hybrid Incompletely dominant Recessive mutant Ans: Incompletely dominant 4. If red color flower is dominant to white flower color, which of the following statement is correct: All red flowered plants form the red flowered plant. A few red flowered plants form the red flowered plants Only white-flowered plants form the white flowered plants Ratio of white to red flowered hybrid plant is 1:1 Ans: Only white-flowered plants form the white flowered plants 5. How many genes a child receives from its father. 25% 75% 50% 100% Ans: 50% 6. Visible characteristics of an organism are called Phenotype Homozygous Genotype heterozygous Ans: Phenotype 7. Two homologous genes are exactly similar in a genotype are called Homozygous Hemizygous Heterozygous None of genes Ans: Homozygous 8. Law of independent assortment can be proved on the basis of which of the following ratios 3:1 9:3:3:1 2:1:1 2:1 Ans: 9:3:3:1 9. Which of the following has the smallest number of chromosome? Onion Monkey Mouse Ascaris Ans: Ascaris 10. Which one of the following is the phenotypic monohybrid ratio in F2 generation 3:1 2:2 1:2:1 1:3 Ans: 3:1 11. The chromosome that determines the sex of the child. X XX Y XY Ans: Y 6. Match Column I with Column II Column I a) b) 1. The fundamental physical and a. functional unit of heredity. b. c) 2. The chromosomes of the same c. shape and size one from each Parent. d) 3. The chromosomes which are not d. associated with sex e) 4. An individual containing two e. complete haploid set of chromosome. f. f) 5. The occurrence of different genes on the same chromosome. g. g) 6. The difference among parents and their offspring. h) 7. Inherited defects which are more common in males related with eyes and blood clotting h. i) 8. The factor or allele which expresses itself phenotypically in the presence of its contrasting allele. i. j) 9. Chromosome constitution of a cell j. or an individual. Column I Column II A. Karyotype. B. Color blindness and haemophilia C. Dominant D. Variation E. Allele F. Diploid G. Autosomes H. Homologous chromosome I. Gene Column II [Answers] k) l) 1. The fundamental physical and k. A. Gene functional unit of heredity. l. m) 2. The chromosomes of the same m. B. Homologous chromosome shape and size one from each Parent. n) 3. The chromosomes which are not C. Autosomes associated with sex o) 4. An individual containing two n. D. Diploid complete haploid set of chromosome. p) 5. The occurrence of different genes o. on the same chromosome. p. q) 6. The difference among parents and their offspring. q. r) 7. Inherited defects which are more common in males related with eyes and blood clotting r. s) 8. The factor or allele which expresses itself phenotypically in the presence of its contrasting allele. s. t) 9. Chromosome constitution of a cell or an individual. E. Allele F. Variation G. Color blindness and haemophilia H. Dominant I. Karyotype. 8. Answer the following questions. 1. What is punnett square? Ans: Punnett square is a simple square shaped diagram in which the different type of gametes of one parent are placed along one side of the square and those of the other parent are placed along the other side. 2. Color blindness is more common in males than in females. Ans: 1.Color blindness is an X linked character. 2.Males have only one X chromosome and Y chromosome . 3.The Y chromosome does not have gene for color blindness. Therefore gene for color blindness when present even in single dose expresses itself. Hence it is more common in male than in females. 3. The sex of the child depends upon the father. Explain Ans: 1.Sex chromosomes in males are heterozygous XY whereas in females it is homozygous XX. 2.If a sperm bearing X chromosome fertilizes with the ovum, XX zygote formed is a female child. 3.If a sperm bearing Y chromosome fertilizes with the ovum XY zygote formed is a male child. hence the sex of the child depends upon the father. 9. State whether the following statements are true or false. If false rewrite the correct form of the statement by only changing the first or last word of the statement. 1. Duplicated chromosome remains attached at a point called centrosome Ans: False, duplicated chromosome remain attached at a point called centromere. 2. The number of pairs of autosome in man is 22. Ans: True. 3. Cytokinesis is a division of cytoplasm. Ans: True. 4. The ova contains XX chromosome. Ans: True 5. Humans have only one sex chromosome. Ans: False, humans have two sex chromosome. 6. Sweet pea was selected as a plant for performing genetic experiments. Ans: False, gardenpea was selected for performing genetic experiment. 7. Variations are produced due to mutation. Ans: True. 8. Chromosomes other than a pair of sex chromosome are called alleles. Ans: False, Chromosomes other than a pair of sex chromosome are called autosomes. SECTION B TYPE QUESTIONS 1. A pure tall plant is crossed with a pure dwarf plant. 1. Draw punnett square to show F1 generation and F2 generation. Ans: Tall plant Dwarf plant Parents TT tt Gametes T t F1 generation gametes t t T Tt Tt T Tt Tt Selfing of F1 generation Parents Tt [heterozygous tall] Gametes T and t F2 generation Gametes T t T TT Tt t Tt tt 2. Give the phenotype of F2 generation. Ans: Phenotype of F2 generation. Tall plant: 3 Dwarf plant: 1 3. Give the phenotype and genotype ratio of the f2 generation. Ans: Phenotypic ratio Genotypic ratio F2 generation: 3:1[Tall : dwarf] 1:2:1[TT:Tt:tt] 4. Name any one X linked disease found in humans. Ans: Haemophilia and colourblindness are X linked disease found in humans. 2. A homozygous tall plant bearing red colored flower is crossed with a homozygous dwarf plant bearing white flowers. 1. Give the genotype and phenotype of f1 generation. Ans: Parents TTRR ttrr Gametes TR tr tr tr TR TtRr TtRr TR TtRr TtRr Phenotype of F1 generation all the plants will be tall with red flowers. Genotype of F1 generation (TtRr.) Heterozygous tall with red flowers. 2. Give the possible combination of gametes that can be obtained from the F1 hybrids. Ans: Genotype F1 generation TtRr[tall plants, red flower] Gametes: TR Tr tR tr 3. Give the dihybrid ratio and the phenotype of the offspring of the F2 generation when two plants of the F1 generation above are crossed. Ans: F2 generation( table only for understanding not to be drawn for this question) TR Tr tR tr TR TTRR TTRr TtRR TtRr Tr TTRr TTrr TtRr Ttrr tR TtRR TtRr ttRR ttRr tr TtRr Ttrr ttRr ttrr Dihybrid ratio: 9:3:3:1 Phenotype: 1. Tall plant, red flowers: 2. Tall plant, white flowers: 3. Dwarf plant, red flowers: 4. Dwarf plant, white flowers: 3. 9 3 3 1 A pure tall plant bearing red coloured flowers was crossed with a pure dwarf plant with white flowers. What would be the nature of offspring in the F1 generation? Ans: In the F1 generation, all the plants will be tall and bear red colored flowers, Parents TTRR X ttrr Gametes TR tr F1 generation: TtRr[ tall, red flowers] All offsprings of F1 generation would be tall and bearing red coloured flowers. 4. Red- green color blindness is a sex linked inherited characteristic. The gene (b) for color blindness is recessive to the gene B for normal vision. The gene b carried only on the X chromosome. B b X X B b X y X Y 1. Describe the phenotypes 1. XX- female, normal vision.[Bb] 2. XY male, red-green color blind.[b] 3. XY male, normal vision.[B] 2. Explain why red-green color blindness is more likely to occur in men then in woman. In male, only one allele from the pair Bb is present. So if recessive factor b for colour blindness is present, it will express as red-green color blindness. 5. Study the following problem based on the crosses involving a single trait and complete the given squares and answers the questions. In a certain species of animals black fur is dominant over brown fur. Predict a genotype and phenotype of the offspring. 1. When both the parents are Bb or have a heterozygous black fur. Ans: genotype of parents - Bb B b B b BB Bb Bb bb Phenotypes 3 black fur. 1 brown fur. Genotype 1 homozygous black fur[BB] 2 heterozygous balckfur[Bb] 1 homozygous brown fur[bb] 2. When one parent is homozygous black and other is homozygous brown. Ans: Homozygous black BB Homozygous brown - bb B B b Bb Bb b Bb Bb Phenotypes All black fur [Bb] Genotype All heterozygous black fur. [Bb] 3. When one parent is heterozygous black and the other is homozygous brown. Ans: Heterozygous black Bb Homozygous brown - bb B b b Bb bb b Bb bb Phenotype 2 black fur[Bb] 2 brown fur[bb] Genotype 2 heterozygous black fur. [Bb] 2 homozygous brown fur. [bb] 6. A homozygous plant having round and yellow seed[RRYY] is crossed with homozygous plant having wrinkled and green seeds[rryy]. 1. Give the scientific name of the plant on which Mendel conducted his hybridization experiments. Ans: Pisum sativum 2. Give the genotype of the F1 generation. Ans: Genotype of parent RRYY rryy Gametes - RY ry RY RY ry RrYy RrYy ry RrYy RrYy Genotype of F1 generation: RrYy 3. Give the dihybrid phenotypic ratio and the phenotype of the offspring of the F2 generation when two plants of the F1 generation are crossed. Ans: Ratio of F2 generation: 9:3:3:1 Gametes of F2 generation : RY rY Ry ry RY RRYY RrYY RRYy RrYy rY RrYY rrYY RrYy rrYy Ry RRYy RrYy RRyy Rryy ry RrYy rrYy Rryy rryy Phenotype of F2 generation: 9 Round and yellow 3 Round and green 3 Wrinkled and yellow 1 Wrinkled and green 4. Name and state the law which explains the dihybrid ratio. Ans: Law of independent assortment. when there are two pairs of contrasting characters, the distribution of the members of one pair into the gamete is independent of the distribution of the other pair 5. Give the possible combinations of the gametes that can be obtained from F1genotype. Ans: F1 genotype: RrYy So possible gamete combinations are: RY round and yellow rY - wrinkled yellow Ry round and green ry - wrinkled and green. 7. Normally only a male child suffers from colorblindness. Explain. Ans: Color blindness is a sex inherited disease in which a person cannot discriminate between certain colors such as red and green. It is due to recessive gene on the X chromosome. It can be explained by the given charts: Case 1 gametes normal mother XX X X X X XC X XC X XC color blind father XCY C X Y Y XY XY 1. All the male offsprings XY have normal vision. 2. All daughters X XC are carriers. Case 2gametes 1 1 1 1 carrier mother XXC X XC X Y female child[XX] normal male child[XY] normal. female [X XC ] carrier. male [XCY] colour blind. normal father XY X Y XC X XC XC Y X XX XY
|
