Covers genetic crosses involving one or two traits (monohybrid and dihybrid) and the use of test crosses to determine genotypes. Practice questions help students apply these methods to solve inheritance problems.
In multiple allelism, a gene has more than two possible alleles in a population, but each individual inherits only two.
Ref: NCERT Class 12 Biology Chapter 4: Principles of Inheritance and Variation Monohybrid Dihybrid and Test Cross
A dihybrid cross with complete dominance results in a phenotypic ratio of 9:3:3:1 in the F2 generation.
Ref: NCERT Class 12 Biology Chapter 4: Principles of Inheritance and Variation Monohybrid Dihybrid and Test Cross
In a monohybrid cross, Mendel observed a phenotypic ratio of 3:1 in the F2 generation.
Ref: NCERT Class 12 Biology Chapter 4: Principles of Inheritance and Variation Monohybrid Dihybrid and Test Cross
Patau syndrome is caused by trisomy of chromosome 13, leading to severe developmental abnormalities.
Ref: NCERT Class 12 Biology Chapter 4: Principles of Inheritance and Variation Monohybrid Dihybrid and Test Cross
Down’s syndrome is caused by trisomy of chromosome 21, leading to developmental and cognitive impairments.
Ref: NCERT Class 12 Biology Chapter 4: Principles of Inheritance and Variation Monohybrid Dihybrid and Test Cross
The expected genotypic ratio in a monohybrid cross (F2 generation) is 1:2:1 (homozygous dominant: heterozygous: homozygous recessive).
Ref: NCERT Class 12 Biology Chapter 4: Principles of Inheritance and Variation Monohybrid Dihybrid and Test Cross
Crossing over during meiosis increases genetic diversity by exchanging genetic material between homologous chromosomes.
Ref: NCERT Class 12 Biology Chapter 4: Principles of Inheritance and Variation Monohybrid Dihybrid and Test Cross
The genotypic ratio of a monohybrid cross (F2 generation) is 1:2:1 (homozygous dominant: heterozygous: homozygous recessive).
Ref: NCERT Class 12 Biology Chapter 4: Principles of Inheritance and Variation Monohybrid Dihybrid and Test Cross
Turner’s syndrome affects females and is caused by the absence of one X chromosome (45, XO).
Ref: NCERT Class 12 Biology Chapter 4: Principles of Inheritance and Variation Monohybrid Dihybrid and Test Cross
A test cross is performed to determine an unknown genotype by crossing with a homozygous recessive individual.
Ref: NCERT Class 12 Biology Chapter 4: Principles of Inheritance and Variation Monohybrid Dihybrid and Test Cross
The Law of Segregation states that two alleles segregate independently into gametes during meiosis.
Ref: NCERT Class 12 Biology Chapter 4: Principles of Inheritance and Variation Monohybrid Dihybrid and Test Cross
A Barr body is an inactivated X chromosome in female cells, ensuring dosage compensation.
Ref: NCERT Class 12 Biology Chapter 4: Principles of Inheritance and Variation Monohybrid Dihybrid and Test Cross
