Class 12 Biology: Principles Of Inheritance And Variation

Class 12 Biology

ID: 1104 Type: Mcq Source: AISSCE(Board Exam) Year: 2025
Question 1: A man whose father was colour-blind marries a woman who had a colour-blind mother and normal father. What percentage of male children of this couple will be colour-blind?
  • A. 25%
  • B. 0%
  • C. 50%
  • D. 75%
ID: 1145 Type: Mcq Source: AISSCE(Board Exam) Year: 2025
Question 2: 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 correct genotypes of father, mother and the child :
Father, Mother, Child
  • A. $I^A i$, $I^B i$, $I^A i$
  • B. $I^A I^B$, $I^A i$, $I^A I^A$
  • C. $I^B i$, $I^A I^B$, $I^A i$
  • D. $I^B I^B$, $I^A I^B$, $I^A I^A$
ID: 1146 Type: Mcq Source: AISSCE(Board Exam) Year: 2025
Question 3: In a pedigree chart $\square \Box$ represents:
  • A. unrelated mating
  • B. affected individuals
  • C. mating between relatives (consanguineous mating)
  • D. Non-identical twins
ID: 1183 Type: Mcq Source: AISSCE(Board Exam) Year: 2025
Question 4: Which of the following conditions correctly describes the manner of determining the sex in the given options ?
  • A. Homozygous sex chromosomes (ZZ) determine female sex in birds.
  • B. XO type of chromosomes determine male sex in grasshoppers.
  • C. XO condition in humans determines female sex.
  • D. Homozygous sex chromosomes (XX) produce male in Drosophila.
ID: 1217 Type: Mcq Source: AISSCE(Board Exam) Year: 2025
Question 5: Study the pedigree chart of a family sharing the inheritance of sickle cell anemia. [Diagram of Pedigree Chart is implied]
The trait traced in the above pedigree chart is :
  • A. Dominant X-linked
  • B. Autosomal dominant
  • C. Recessive X-linked
  • D. Autosomal recessive
ID: 1219 Type: Mcq Source: AISSCE(Board Exam) Year: 2025
Question 6: Which of the following do not follow the law of independent assortment ?
  • A. Genes on non-homologous chromosomes and absence of linkage
  • B. Two or more genes on homologous chromosomes
  • C. Linked genes located on the same chromosomes
  • D. Two or more distant genes present on the same chromosome
ID: 1248 Type: Mcq Source: AISSCE(Board Exam) Year: 2025
Question 7: Which of the following is not an example of aneuploidy ?
  • A. Turner's syndrome
  • B. Down's syndrome
  • C. Phenylketonuria
  • D. Klinefelter's syndrome
ID: 1253 Type: Mcq Source: AISSCE(Board Exam) Year: 2025
Question 8: During a monohybrid cross involving a tall pea plant with a dwarf pea plant, the offspring populations were tall and dwarf in equal ratio. Find out the genotype of parent pea plants.
  • A. $Tt \times tt$
  • B. $TT \times Tt$
  • C. $tt \times tt$
  • D. $Tt \times Tt$
ID: 1260 Type: Mcq Source: AISSCE(Board Exam) Year: 2025
Question 9: Which of the following is not an example of aneuploidy ?
  • A. Turner's syndrome
  • B. Down's syndrome
  • C. Phenylketonuria
  • D. Klinefelter's syndrome
ID: 1265 Type: Mcq Source: AISSCE(Board Exam) Year: 2025
Question 10: During a monohybrid cross involving a tall pea plant with a dwarf pea plant, the offspring populations were tall and dwarf in equal ratio. Find out the genotype of parent pea plants.
  • A. $Tt \times tt$
  • B. $TT \times Tt$
  • C. $tt \times tt$
  • D. $Tt \times Tt$
ID: 1272 Type: Mcq Source: AISSCE(Board Exam) Year: 2025
Question 11: Which of the following is not an example of aneuploidy ?
  • A. Turner's syndrome
  • B. Down's syndrome
  • C. Phenylketonuria
  • D. Klinefelter's syndrome
ID: 1277 Type: Mcq Source: AISSCE(Board Exam) Year: 2025
Question 12: During a monohybrid cross involving a tall pea plant with a dwarf pea plant, the offspring populations were tall and dwarf in equal ratio. Find out the genotype of parent pea plants.
  • A. $Tt \times tt$
  • B. $TT \times Tt$
  • C. $tt \times tt$
  • D. $Tt \times Tt$
ID: 1284 Type: Mcq Source: AISSCE(Board Exam) Year: 2025
Question 13: In the given pedigree chart, a cross between a normal couple resulted in a son who was haemophilic and a normal daughter. In course of time, when the daughter was married to a normal man, to their surprise the grandson was also haemophilic.
Choose the option that indicates the correct inheritance of trait in the above pedigree chart :
  • A. Autosome linked dominant trait
  • B. Sex-linked dominant trait
  • C. Autosomal recessive trait
  • D. Sex-linked recessive trait
ID: 1292 Type: Mcq Source: AISSCE(Board Exam) Year: 2025
Question 14: In a pea plant (Pisum sativum) inflated pod shape is dominant over constricted pod shape. The expected ratio of phenotypes of the offspring in a cross between both the parents with heterozygous inflated pod shape will be
  • A. 1:0
  • B. 1:1
  • C. 2:1
  • D. 3:1
ID: 1314 Type: Mcq Source: AISSCE(Board Exam) Year: 2025
Question 15: A single gene that controls the expression of more than one trait is said to show
  • A. Multiple allelism
  • B. Polygenic inheritance
  • C. Incomplete dominance
  • D. Pleiotropism
ID: 1315 Type: Mcq Source: AISSCE(Board Exam) Year: 2025
Question 16: A person with trisomy of 21st chromosome shows
  • (i) Furrowed tongue
  • (ii) Characteristic palm crease
  • (iii) Rudimentary ovaries
  • (iv) Gynaecomastia
Select the correct option, from the choices given below :
  • A. (ii) and (iv)
  • B. (i), (ii) and (iv)
  • C. (ii) and (iii)
  • D. (i) and (ii)
ID: 1322 Type: Mcq Source: AISSCE(Board Exam) Year: 2025
Question 17: Study the pedigree chart of a family showing the inheritance pattern of a certain disorder. Select the option that correctly identifies the nature of the trait depicted in the pedigree chart.
[Pedigree Chart]
  • A. Dominant X – linked
  • B. Recessive X – linked
  • C. Autosomal dominant
  • D. Autosomal recessive
ID: 1324 Type: Mcq Source: AISSCE(Board Exam) Year: 2025
Question 18: If both the parents are carriers for thalassaemia, the chances of an afflicted child to be born to them is :
  • A. 25%
  • B. 50%
  • C. 75%
  • D. 100%
ID: 1119 Type: Assertion-reason Source: AISSCE(Board Exam) Year: 2025
Question 19: Assertion (A): When the two genes in a dihybrid cross are situated on the same chromosome, the proportion of parental gene combinations is much higher than non-parental type. Reason (R): Higher parental gene combinations can be attributed to crossing over between two genes.
ID: 1193 Type: Assertion-reason Source: AISSCE(Board Exam) Year: 2025
Question 20: Assertion (A): A male individual always inherits haemophilia from his mother.
Reason (R): The gene for haemophilia lies on X-chromosome.
ID: 1224 Type: Assertion-reason Source: AISSCE(Board Exam) Year: 2025
Question 21: Assertion (A): In dihybrid crosses involving sex-linked genes in Drosophila generation of non-parental gene combinations are observed.
Reason (R): Two genes present on different chromosomes show linkage and recombination in Drosophila.
ID: 1296 Type: Assertion-reason Source: AISSCE(Board Exam) Year: 2025
Question 22: Assertion (A): ABO blood grouping in humans is an example of multiple allelism.
Reason (R): More than two genes in a population govern the same character in ABO blood grouping in humans.
ID: 1328 Type: Assertion-reason Source: AISSCE(Board Exam) Year: 2025
Question 23: **Assertion (A):** In birds the sex of the offspring is determined by males.
**Reason (R):** Males are homogametic while females are heterogametic.
ID: 1124 Type: Very short (VSA) Source: AISSCE(Board Exam) Year: 2025
Question 24: Study the cross given below : Parents: $44+\text{XY}$, $44+\text{XX}$. Gametes: $22+\text{XY}$, $22+\text{O}$, $22+\text{X}$, $22+\text{X}$. Offsprings: $1$, $2$. Identify the abnormalities '1' and '2' in the offsprings of a cross done between a couple and distinguish between them.
ID: 1125 Type: Very short (VSA) Source: AISSCE(Board Exam) Year: 2025
Question 25: Study the pedigree chart given below, showing the inheritance pattern of blood group in a family: [Diagram]. Answer the following questions: (a) Give the possible genotypes of individual 1 and 2. (b) Which antigen or antigens will be present on the plasma membranes of the R.B.Cs of individuals '5' and '8'?
ID: 1161 Type: Very short (VSA) Source: AISSCE(Board Exam) Year: 2025
Question 26: Study the given pedigree chart in which neither of the parents shows the trait but the trait is present in both male and female children. [Diagram is implied but not provided in text]
(a) Write about the trait, also explain the inheritance of such trait in the progeny on the basis of given pedigree chart.
(b) Give one example of such trait in human beings.
ID: 1199 Type: Very short (VSA) Source: AISSCE(Board Exam) Year: 2025
Question 27: A karyotype of a human suffering from a certain disorder is given below : [Diagram is implied, showing an extra X chromosome for a male]
  • (a) Identify the disorder.
  • (b) Write the symptoms of the disorder.
  • (c) Give reason for such a disorder.
ID: 1169 Type: Short (SA) Source: AISSCE(Board Exam) Year: 2025
Question 28: Using a Punnett square workout the distribution of an autosomal phenotypic feature in the first filial generation after a cross between a homozygous female and a heterozygous male for a single locus.
ID: 1235 Type: Short (SA) Source: AISSCE(Board Exam) Year: 2025
Question 29: Answer the following questions with respect to the sex determining mechanism observed in honey bee.
  • (a) Name the type of sex determination system observed in honey bee.
  • (b) Fill in the blanks (i), (ii) and (iii) in the given question.
    [Table is implied with columns: Parent, Male, Type of cell division during gamete formation, Number of chromosomes in gametes, Number of chromosomes in diploid cell of progeny]
  • (c) What will be the sex and chromosome number of the progeny formed from the unfertilised eggs of honey bee ?
ID: 1303 Type: Short (SA) Source: AISSCE(Board Exam) Year: 2025
Question 30: Gregor Mendel conducted hybridisation experiments in garden pea for seven years and proposed the law of inheritance.
(a) Why was he successful in his hybridisation experiments ? Give two reasons.
(b) State the law of independent assortment as proposed by Mendel after his dihybrid crosses.