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NUMERICAL PROBLEMS ON ICSE AND ISC GENETICS

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Sumit Roy
Sri Sri Academy (SSA), Kolkata

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NUMERICAL PROBLEMS ON ICSE & ISC GENETICS 1. What type of children will appear in F1 generation if a colour blind man marries with a normal woman? Gene for colour blindness is Xc and gene for normal vision is Xc+. 2. Gene A is dominant over gene a. What will be the phenotypic ratio in the offspring obtained from the following mating?(a) Aa X aa. (b) Aa X AA. (c) Aa X Aa. 3. In humans pointed eyebrows is dominant over smooth eyebrows. Rahul s father has pointed eyebrows but he and his mother has smooth eyebrows. Predict the following:(a) Give the genotype of Rahul. (b) What will be the genotype of his father and mother? (c) If Rahul marries a woman who is heterozygous, what will be the possible genotype of the offspring in the next generation? State the % probability of having homozygous dominant, homozygous recessive and heterozygous dominant. 4. A haemophilic man marries a normal homozygous woman. What is the probability that their daughter will be haemophilic? 5. In a certain mammal curly hair is dominant over straight hair. In a cross between the two in the F2 generation, three had curly hair and one had straight hair. (a) What would be the genotype of parents? (b) Work out the genetic cross. 6. What happens when a red coloured homozygous Antirrhinum is crossed with a homozygous white coloured plant? Work out the genotype and phenotype. 7. A cross is made between Tall plant with Yellow seeds (TtYy) and a tall plant with green seeds (Ttyy). What proportion of phenotype would be expected in the offspring to be (a) Tall and green (b) Dwarf and green. 8. A man with AB blood group marries a woman of O blood group. Work out the possible genotype and phenotype of the progeny. 9. A heterozygous Smooth seeded and Red flowered pea plant is crossed with homozygous recessive rough seeded white flowered plant. Determine the progeny. 10. A man with blood group A marries a woman with blood group B. Their first child has blood group O. Give their genotype. Also find out what other blood groups will other children bhave of the same couple. 11. Ravi s parents have normal colour vision but his maternal grandfather is colourblind. Gene for colour vision is located on the X chromosome. (a) Work out a cross, showing the percentage of chances of Ravi and his siblings being colour blind. (b) What is the genotype of mother. (c) State the type of inheritance being shown in the above cross. 12. A haemophilic man marries a carrier woman. Obtain phenotypes of offspring using Punnett square.What is Y- linked inheritance? 13. A normal visioned woman marries a normal visioned man. They have a colour blind child.How can it be explained? Use Punnett square to substantiate your answer. 14. In Mirabilis jalapa the red colour of flower is incompletely dominant over white, the heterozygous condition being pink. What will be the phenotype and genotype and their ratios in the following crosses:(a) Red and Pink. (b) White and Pink. (c) Pink and Pink. 15. Some dogs bark while trailing while others are silent. The barking trait is due to dominant gene. Erect ears are dominant over drooping ears. What kind of puppies would be expected from the heterozygous erect eared barker mated to a droop silent trailer? 16. In an experiment on Lathyrus odoratus, a cross was made between a plant having purple flower (PPCC) and one having white flowers (ppcc). In the F1, all plants had purple flowers and in F2, it was a modified Mendelian ratio. Work out the cross using Punnett square and explain the inheritance.. 17. A man with blood group A marries a woman with B blood group. Find out the genotypes and the blood groups of their children, when (a) Both parents are heterozygous. (b) Both parents are homozygous. (c) Man is heterozygous and female is homozygous. (d) Man is homozygous and female is heterozygous. 18. Zicco s parents have normal colour vision but his maternal grandfather is colour-blind. Gene for colour vision is located on the X chromosome. (a) Work out a cross showing showing the percent chances of Zicco and his siblings being colour blind, normal or carrier. (b) What is the genotype of his maternal grandfather? 19. If the percentage of adenine in the genome is 40%, what will be the percentage of cytosine in it? 20. When a person with no antigens in his blood is married to a woman with blood group A. What would be the possible blood groups of their offspring? 21. Cystic fibrosis is a recessive condition that affects about 1 in 2500 babies in the Caucasian population of the US. Calculate the frequency of recessive and dominant allele in the population. 22. A haemophilic man marries a carrier woman. Find out the genotypes of the offspring. 23. A diploid organism is heterozygous for 4 loci, how many types of gametes can be produced? 24. Using a Punnett Square, workout the distribution of phenotypic features in the first filial generation after a cross between a homozygous female and a heterozygous male for a single locus. 25. When a cross in made between tall plant with yellow seeds (TtYy) and tall plant with green seed (Ttyy), what proportions of phenotype in the offspring could be expected to be (a) Tall and green. (b) Dwarf and green. 26. Two heterozygous parents are crossed. If the two loci are linked what would be the distribution of phenotypic features in F1 generation for a dihybrid cross? 27. The crossing over frequencies between genes are as follows: A & B = 8%, B & C = 8.5%, C & D = 18.5%, A & C = 16.5% and B & D = 10%. Work out their sequence and relative positions on a segment of a chromosome. 28. A child has blood group O. If the father has blood group A and mother blood group B. Work out the genotypes of the parents and the possible genotypes of the other offsprings. 29. If a double stranded DNA has 20 per cent of cytosine, calculate the percent of adenine in the DNA. 30. If the sequence of one strand of DNA is written as follows: 5'-ATGCATGCATGCATGCATGCATGCATGC-3'. Write down the sequence of complementary strand in 5' 3' direction 31. If the sequence of the coding strand in a transcription unit is written as follows: 5'-ATGCATGCATGCATGCATGCATGCATGC-3' Write down the sequence of mRNA. 32. What will be the probability of the children with A blood type if mother has AB blood group and father is heterozygous for B blood group? 33. In humans, brown eyes (B) are dominant over blue (b). A brown- eyed man marries a blue eyed woman and they have three children, two of whom are brown eyed and one of whom is blue eyed. Draw a Punnett square that illustrates this marriage. (a) What is the man s genotype? (b) What are the genotypes of the children? 34. A red (R) colour pea flower is crossed with a white (r) colour pea flower. Predict the following:(a) What type of genetic cross is given above? Justify. (b) What is the nature of offspring in the F1 generation? (c) State the phenotypic ratio and phenotypic % probability of F2 progeny using Punnett square. (d) State the genotypic ratio and genotypic % probability of F2 progeny. (e) State the law enunciated in the above cross. Who proposed the law? 35. A tall (TT) pea plant with red (RR) colour flower is crossed with a dwarf (tt) pea plant with white (rr) colour flower. Predict the following:(a) What type of genetic cross is given above? Justify. (b) What is the nature of offspring in the F1 generation? (c) What are the possible combinations of gametes for the F2 generation? (d) State the phenotypic ratio and phenotypic % probability of F2 progeny using Punnett square. (e) State the genotypic ratio and genotypic % probability of F2 progeny using Punnett square. (f) If a heterozygous F1 offspring is crossed with homozygous recessive parent, what type of cross will it be? State the ratio of such cross. (g) State the law enunciated in the above cross. Who proposed the law? 36. In human beings blue eye colour is recessive to brown eye colour. A brown eyed man has a blue eyed mother. (a) What is the genotype of the man and his mother? (b) What are the possible genotypes of his father? (c) If the man marries a blue eyed woman, what are the possible genotypes of their offspring? 37. In Drosophila, white eye colour is recessive to red eye colour and sex linked. If a white eyed female is crossed with a red eyed male and an F1 male with a white eyed female, what will be the appearance as to eye colour of the offspring of these last two crosses? 38. In Drosophila, a mutant gene vermilion (v) for light eye colour is recessive to red eye (V) and located in the X chromosome. If a vermilion female is crossed with a red eyed male, what will be the eye colour of the F1 and F2 individuals? 39. A girl of normal vision whose father was also colour blind marries a man of normal vision whose father was also colour blind. What type of vision can be expected in their offsprings? 40. A colour blind woman marries a man with normal vision. What kind of children would be expected in their offspring? 41. A red green colour blind man marries a normal woman whose father was colour blind. They have eight children, 4 boys and 4 girls. Assuming an equal distribution of colour-blindness and normal vision among the children, how many of each would be expected for the two sexes? 42. A woman whose father was a haemophilic marries a normal man. If they have eight children , 4 boys and 4 girls. How many haemophilies would be expected among them? Show the expected results by a diagram. 43. A man has Hypertrichosis of the ears, a condition which appears to be due to a gene on the nonhomologous portion of the Y chromosome. He marries a normal woman. Show the types of children which they may expect to have. 44. When a tall pea plant was self pollinated, one- fourth of the progeny was dwarf. Give the genotype of the parent and dwarf progenies. 45. 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 genetic cross. 46. A man with blood group A married a woman with B blood group and a daughter with blood group O. Work out the cross and show the possibility of such inheritance. 47. A pure tall plant (TT) is crossed with pure dwarf plant (tt). Draw Punnett squares to show F1 and F2 generation. Give the phenotype and Genotype of the F1 and F2 generation. 48. A normal visioned woman marries a normal visioned man. They have a colour blind son. How can it be explained? Use Punnet square to substantiate your answer. 49. A heterozygous tall pea plant is crossed with a homozygous dwarf pea plant. With the help of a Punnett square, show the parents and their offsprings Phenotypes and Genotypes. 50. A haemophilic man marries a carrier woman. Obtain phenotypes and genotypes of offsprings using Punnett square. 51. Given below is a table showing the genotypes and the phenotypes of blood groups in the human population:- Genotype Phenotype W A B B II Y IAIB Z X O (a) Identify the genotypes W and X and the phenotypes Y and Z. (b) How is Co-dominance different from Incomplete dominance? (c) Name the pattern of inheritance exhibited by the phenotypes Y and Z in the table. 52. Let Y be the genotypic symbol for the dominant yellow seed colour, symbol y for recessive green seed colour, symbol R for dominant round shape of the seed and symbol r for recessive wrinkled seed shape in the garden pea. Using these symbols, explain Mendel s law of Independent Assortment. 53. Human skin colour is believed to be controlled by at least three separate genes (a) What do you can this type of inheritance? (b) Suppose the genes are designated as A, B and C and the darkness are dominant over fairness, what shall be the genotypes of the darkest, fairest and intermediate skin colour? (c) What will be the total number of allele combinations in the gametes of a person heterozygous for all the three genes? 54. Determine the order of the genes along a chromosome based on the following recombination frequencies:A-B 8mu, A-C 28mu, B-C 20 mu, B-D 33 mu. 55. Ashok parents have normal colour vision but his maternal grandfather is colour blind. (a) Work out a cross showing percent changes of Ashok and his siblings being colour blind. (b) What is the genotype of his mother? (c) What is the term used for this kind of inheritance? Mention two specialties of such inheritance. 56. A normal woman whose mother was colour blind has a son. Nothing is known of the colour vision phenotype of the father. What is the probability that the son will be colour blind? Prepared by:Mr. Sumit Roy [Asst. Biology Teacher] (9830431393/9874577160/7044929409) Post Graduate Diploma in Environmental Biotechnology (C.U.) M.Sc (Zoology), Gold Medalist of Vidyasagar University, B.Ed E mail: - sumitroy888@gmail.comsumit@ssa.org.in

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