Principles of Inheritance and Variation

CBSE Class 12 Biology · every board question from this chapter, 2023–2026 · 40 of them repeated across years

• Which one of the following statements is correct?2026
• Which of the following traits studied by Mendel in pea plant is a recessive trait?2026
• In a dihybrid cross, 2400 individuals are produced in F 2 generation. Approximately how many will be phenotypically similar to…2026
• A woman having genes for haemophilia on one X chromosome and a gene for colour blindness on another X chromosome marries a normal…2026
• In Pisum sativum, the flower colour may be violet (V) or white (v). What proportion of the offspring in a cross of 'VV' × 'vv'…2026asked 2×
• Which of the following amino acid substitutions is responsible for causing sickle cell anemia?2026
• Select the correct statement. All genes located on the same chromosome:2026
• Thorns of Bougainvillea and tendrils of Cucurbita are examples of:2026
• If a genetic disease is transferred from a phenotypically normal but carrier female to only some of the male progeny, the disease…2026
• What would be the minimum possibility of a dominant trait being expressed in an offspring after a monohybrid test cross?2026
• Study the given pedigree and identify the disease represented.2026
• In the following figure, two ways of pairing of two homologous pairs of chromosomes are shown. Which of the following phenomena…2026asked 2×
• Assertion: The human blood group 'AB' exemplifies co-dominance. Reason (R): The gene for human blood group trait exists in three…2026asked 2×
• Is it possible for a trait to be inherited by an organism but not expressed in its phenotype? Justify and illustrate your answer…2026
• Study the figures given below and answer the questions. Cross - A Cross - B Identify in which of the crosses the strength of…2026
• State any four reasons why Mendel succeeded in his genetic hybridisation experiments on garden peas.2026
• Study the schematic cross between male and female honey bee given below and answer the questions that follow. Identify the cell…2026
• What did Henking observe in his experiments on insects that led to the discovery of sex chromosome? How did his observation…2026
• Mendel published his work on inheritance in 1865, but it remained unnoticed for over three decades. State the reasons why his…2026
• Analyse the following two cases of sex determination in different organisms: Case I: Males have (XO) sex chromosomes and females…2026asked 2×
• A child is born with a genetic disorder due to the deletion of a gene. Name such a gene studied by you. Explain how gene therapy…2026
• Give the scientific name of the organism used by Morgan to study sex-linked traits. Write any four reasons why this organism made…2026asked 3×
• What is pedigree analysis? Mention its importance in human genetics. (2 pts.) Analyse the following pedigree and write the (i)…2026
• Explain the polygenic inheritance pattern with the help of a suitable example.2026
• Describe the experiment conducted by T.H. Morgan on Drosophila melanogaster involving eye colour and body colour. How did the…2026asked 3×
• A student performed some crosses in plants and represented the result in the form of bar graphs as shown below. Each graph…2026asked 3×
• Write the types and locations of the genes causing thalassemia in humans. State the cause and symptoms of the disease. How is…2026asked 3×
• Work out separate monohybrid crosses up to F 2 generation between two pea plants and two Antirrhinum plants, both having…2026asked 3×
• A man whose father was colour-blind marries a woman who had a colour-blind mother and normal father. What percentage of male…2025asked 3×
• The given graph shows the range of variation among population members, for a trait determined by multiple genes. If this…2025asked 2×
• When a pure tall pea plant (Pisum sativum) with green pod is crossed with dwarf pea plant with yellow pod, how many dwarf pea…2025
• In a pedigree chart, if two unaffected individuals have a child with the trait, what is the most likely mode of inheritance for…2025
• The number of autosomes present in a human secondary spermatocyte2025asked 2×
• Thalassemia and Sickle Cell Anaemia are both caused due to problem in globin molecule synthesis. Select the correct statement:2025
• A child with blood group A has father with blood group B and the mother with blood group AB. Choose the option that gives the…2025asked 3×
• Inheritance of which of the following traits is shown in the cross given below? Choose the correct option from the following:2025
• In a pedigree chart ' ' represents:2025asked 2×
• Which of the following is not an example of aneuploidy?2025
• In the given pedigree chart, a cross between a normal couple resulted in a son who was haemophilic and a normal daughter. In…2025
• Study the pedigree chart of a family showing the inheritance of myotonic dystrophy: The trait under study is:2025
• In the pedigree chart given below, what should be the genotype of the indicated member?2025
• A Dihybrid cross is done between two parent pea plants (pure line) who differ in two pairs of contrasting traits: Seed colour and…2025
• A colourblind man marries a woman with normal sight who has no history of colourblindness in her family. What is the probability…2025
• A pedigree chart in shown below for a disease that is autosomal dominant. The genetic make-up of the first generation is:2025
• Which of the following conditions correctly describes the manner of determining the sex in the given options?2025asked 2×
• A dwarf pea plant was treated with gibberellic acid and it becomes as tall as a tall pea plant. If these treated pea plants are…2025
• Which of the following features correctly show the mechanism of sex- determination in honey-bees? (i) A zygote formed from the…2025
• A normal couple produces half the sons as haemophilic and half the daughters as carriers. Choose the option that correctly…2025
• Study the pedigree chart of a family sharing the inheritance of sickle cell anemia. The trait traced in the above pedigree chart…2025
• Which of the following do not follow the law of independent assortment?2025
• Match the terms in Column-I with their description in Column-II and choose the correct option.2025
• During a monohybrid cross involving a tall pea plant with a dwarf pea plant, the offspring populations were tall and dwarf in…2025
• A diploid organism is heterozygous for three loci, how many types of gametes can be produced by that organism?2025
• Which of the following is correct for the condition when plant YyRr is back crossed with the double recessive parent?2025
• In a pea plant (Pisum sativum), green pod colour is dominant over yellow pod colour. The expected ratio of the phenotypes of the…2025
• In a pea plant (Pisum sativum) inflated pod shape is dominant over constricted pod shape. The expected ratio of phenotypes of the…2025
• In pea plant (Pisum sativum) axial flower position is dominant over terminal flower position. The expected ratio of phenotypes of…2025
• Assertion: In dihybrid crosses involving sex-linked genes in Drosophila generation of non-parental gene combinations are…2025asked 3×
• Assertion: 'XX - XY' type of sex-determination mechanism is an example of male heterogamety. Reason (R): In birds male…2025
• Assertion: Human male is referred to as heterogametic. Reason (R): The male produces millions of sperms of the same kind.2025
• Assertion: Gene pairs present on the same chromosome may be tightly linked or loosely linked. Reason (R): Frequency of…2025asked 3×
• Assertion: A male individual always inherits haemophilia from his mother. Reason (R): The gene for haemophilia lies on…2025asked 2×
• Assertion: ABO blood grouping in humans is an example of multiple allelism. Reason (R): More than two genes in a population…2025asked 3×
• Assertion: When the two genes in a dihybrid cross are situated on the same chromosome, the proportion of parental gene…2025asked 2×
• Study the two different crosses given below: Identify the abnormalities 1 and 2 in the offsprings of given crosses and…2025
• Study the pedigree analysis given below: Answer the following questions: Write genotypes of c and d. Identify whether the trait…2025
• Study the two different crosses given below: Identify the abnormalities '1' and '2' in the offsprings of given crosses and…2025
• Study the pedigree analysis of Myotonic dystrophy given below: Answer the following questions: Write genotype of A, B, C and D…2025
• Study the given pedigree chart in which neither of the parents shows the trait but the trait is present in both male and female…2025asked 2×
• Write two closely linked genes that control α -thalassemia. Differentiate between thalassemia and sickle cell anaemia on the…2025
• Study the cross given below: Identify the abnormalities '1' and '2' in the offsprings of a cross done between a couple and…2025
• Study the pedigree chart given below, showing the inheritance pattern of blood group in a family: Answer the following questions:…2025
• A karyotype of a human suffering from a certain disorder is given below: Identify the disorder. Write the symptoms of the…2025asked 2×
• Write the scientific name of the fruit fly. Why did Morgan prefer to work with fruit flies for his experiments? State two reasons.2025
• Gregor Mendel used true-breeding pea lines to conduct his hybridisation experiments in garden pea. Explain what is meant by…2025
• During a medical investigation, an infant was found to possess an extra copy of chromosome no. 21. Identify the disorder the…2025
• Study the diagram above and answer the following questions: How many alleles are involved in blood grouping? A person having 'AB'…2025asked 3×
• Gregor Mendel conducted hybridisation experiments in garden pea for seven years and proposed the law of inheritance. Why was he…2025
• Using a Punnett square workout the distribution of an autosomal phenotypic feature in the first filial generation after a cross…2025asked 3×
• Answer the following questions with respect to the sex determining mechanism observed in honey bee. What is the type of cell…2025
• Answer the following questions with respect to the sex determining mechanism observed in honey bee. Name the type of sex…2025
• Name one commonly occurring genetic disorder in humans which is caused due to monosomy (one chromosome less than the normal…2025
• Answer the following questions with respect to the sex determination mechanism in birds: Name the type of heterogamety observed…2025
• Name a blood related autosomal Mendelian disorder. Why is it called as Mendelian disorder? How is the disorder transmitted from…2025
• Thomas Hunt Morgan carried out several dihybrid crosses in Drosophila melanogaster to study genes that were sex linked. Give four…2025
• Student to attempt either option- or. (i) You are given axial pea flowers with violet colour whose genotypes are unknown. How…2025
• (i) What is a test cross? How can we find out the zygosity of a plant by the use of test cross? (ii) Why are human females rarely…2025
• Student to attempt either option- or: (i) Haemophilia and red green colourblindness is usually observed in men. Why? (ii) Perform…2025
• Student to attempt either option- or: (i) Perform a cross between two sickle cell carriers. What ratio is obtained between…2025
• A single gene that controls the expression of more than one trait is said to show2024
• Refer to the Venn diagram given below. Select the option with correct examples P, Q, and R:2024
• A person with trisomy of 21^ st chromosome shows (i) Furrowed tongue (ii) Characteristic palm crease (iii) Rudimentary ovaries…2024asked 3×
• Match the items in Column I with those in Column II and select the correctly matched option from those given below:2024
• Which one of the following chromosomal event will not result in genetic variation amongst the offsprings?2024
• In humans, the secondary oocyte completes meiotic division when:2024
• Identify the category of genetic disorder depicted in the pedigree chart given below:2024asked 3×
• Select the incorrect match from the following: Human Karyotype Characters2024asked 2×
• A Snapdragon plant bearing pink colour flowers is crossed with a Snapdragon plant bearing white colour flowers. The expected…2024
• Which one of the following option denotes mating between relatives in human pedigree analysis?2024
• In which of the given chromosomal disorders does the individual have tall stature with feminised character?2024
• In which of the following chromosomal disorders do the individuals have short stature, small head, furrowed tongue and partially…2024
• The expected phenotypic ratio amongst the progeny of 60 individuals, obtained from a cross between heterozygous tall pea plant…2024
• A Snapdragon plant bearing red colour flowers was crossed with a Snapdragon plant bearing white colour flowers. The F 1 progeny…2024
• A Snapdragon plant bearing pink colour flowers is crossed with a Snapdragon plant bearing white colour flowers. Their F 1 progeny…2024
• In which of the following chromosomal disorders do individuals have short stature, underdeveloped feminine character and sterile…2024
• Turner's syndrome in humans occurs due to2024asked 3×
• A woman with normal vision has a colour blind father. She marries a man with normal vision. The percentage chance of their…2024
• Study the pedigree chart of a family showing the inheritance pattern of a certain disorder. Select the option that correctly…2024asked 3×
• If both the parents are carriers for thalassaemia, the chances of an afflicted child to be born to them is:2024
• Match the items in Column I with those in Column II and select the correctly matched option from those given below: Column I…2024asked 2×
• Which of the chromosome in a human possesses the least number of genes?2024
• The human chromosome with the highest and least number of genes in them are respectively:2024
• Assertion: Linked genes do not show dihybrid F 2 ratio 9: 3: 3: 1. Reason (R): Linked genes do not undergo independent assortment.2024asked 2×
• Assertion: In birds the sex of the offspring is determined by males. Reason (R): Males are homogametic while females are…2024asked 2×
• Although Haemophilia and sickle cell anemia are two blood related Mendelian disorders, yet, they differ in their pattern of…2024asked 3×
• With reference to flower colour two independent crosses were made, one between true breeding garden pea plants and another…2024
• A man with blood group 'A' marries a woman with blood group 'AB'. The first child born to them has blood group 'B'. Work out a…2024
• Three crosses were carried out in pea plants with respect to flower colour violet/white (V/v) and flower position axial/terminal…2024
• Explain the mechanism of haplo-diploid pattern of sex determination with the help of a suitable example. Why is this pattern so…2024
• "Human blood group (ABO group) inheritance is a good example of multiple allelism and co-dominance." Justify the statement.2024
• In a family, the father, the daughter and the son are colour blind, whereas the mother has normal vision. Do you think the son…2024asked 2×
• Expression of different genes for different traits may show dominance, incomplete dominance or co-dominance. Write about…2024
• Given below is a picture that shows the magnified blood smear of a patient under a microscope. Name the disease the blood smear…2024
• A pea plant with purple flowers, when crossed with a plant with white, produced 50 plants with only purple flowers. On selfing…2024
• Stability, as one of the properties of genetic material, was very evident in one of the very early experiments in genetics. Name…2024asked 2×
• (i) Compare the pattern of inheritance of flower colour in garden pea plant (violet/white) with snapdragon plant (red/white) on…2024
• Many patterns of inheritance deviate considerably from the pattern of inheritance as explained by Mendel. List any four such…2024
• "The influence of both the alleles in a heterozygous state is clearly expressed in codominance." Explain with the help of…2024asked 3×
• (i) State Mendel's law of independent assortment. (ii) Explain this law by taking the example of a cross between two heterozygous…2024
• Work out a dihybrid cross upto F 2 generation between pea plants bearing violet coloured axial flowers and white coloured…2024
• Which one of the following processes results in the production of recombinants in future generations? (i) Mutation (ii)…2023
• Three genes R, S and T are located on the same chromosome. If the recombinant percentage between R and S is 20 %, R and T is 35 %…2023
• Choose the set of sex determining chromosomes that indicates the correct sex of the respective organism.2023
• Which of the following statements are true about the males in a colony of honey bees? (i) They have 16 chromosomes per cell. (ii)…2023
• Assertion: In humans the genotype with all the dominant alleles (AABBCC) will have the darkest skin colour. Reason (R): In a…2023
• Assertion: In a monohybrid cross between tall plants and dwarf plants, the F 2 generation showed tall and dwarf plants in the…2023
• Assertion: In Thalassemia an abnormal myoglobin chain is synthesized due to a gene defect. Reason (R): α -Thalassemia is…2023asked 3×
• Assertion: Birds like pigeon have heterogametic females whereas the males are homogametic. Reason (R): In pigeons, females have Z…2023
• By using Punnett square depict the genotypes and phenotypes of test crosses (where green pod colour (G) is dominant over yellow…2023asked 3×
• Study the given pedigree chart and answer the questions that follow. Is the trait given in the chart dominant or recessive? Give…2023
• Study the pedigree chart of a family given below and answer the questions that follow: Is the disease in this pedigree chart a…2023
• Study the pedigree chart given below and answer the questions that follow: (i) Is this trait recessive or dominant? Give reason.…2023
• The chromosome number is fixed for all normal organisms leading to species specification whereas any abnormality in the…2023asked 3×
• The following pedigree chart shows the inheritance of a genetic disorder up to three generations of a family. Observe the chart…2023asked 3×
• "It is sometimes observed that the F 1 progeny shows a phenotype that resembles both the parents." Explain this type of…2023

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