NEET · Biology —

Principles of Inheritance and Variation appeared 7 times across 1 year — 7.8% of Biology. This question is from Genetic Disorders.

Year 2024 Total
Questions 7 7
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The sixth mutant codon of beta globin gene causing polymerization of Haemoglobin and change in RBC shape is ____.

Solution & Explanation

Core Logic

Sickle cell anaemia is caused by a point mutation at the sixth position of the beta globin chain. The normal codon is GAG, which codes for Glutamic acid. The mutation changes this normal codon to GUG on the mRNA, which codes for Valine. This mutant valine causes hemoglobin molecules to polymerize under low oxygen tension, changing the RBC shape to sickle-like.

Step 1: Final Conclusion

The mutant codon is GUG.

Pattern Recognition

GAG = Normal (Glutamic Acid). GUG = Mutant (Valine). The question explicitly asks for the 'mutant codon'.

Chapter Mix

Class 12 Biology: Principles of Inheritance and Variation Class 12 Biology: Molecular Basis of Inheritance

Reference Study Guides

Principles Of Inheritance And Variation

More Principles of Inheritance and Variation Previous-Year Questions — Page 2

Q154 neet_2026_03_may_morning Sex Determination
In a population of a grasshopper species, the chromosome number of some members is 23 and some other members possess 24 chromosomes. The 23 and 24 chromosome-bearing members in this species are
  • A. all males
  • B. all females
  • C. females and males, respectively
  • D. males and females, respectively

Solution

Core Logic

In grasshoppers, sex determination is of the XX-XO type. Males have only one X chromosome besides the autosomes (XO), whereas females have a pair of X chromosomes besides the autosomes (XX). Therefore, an individual with 23 chromosomes (one less sex chromosome) is a male grasshopper, and the one with 24 chromosomes is a female grasshopper.

Pattern Recognition

Insects like grasshoppers follow XO male heterogamety. Males always have one chromosome less than females.

Chapter Mix

Class 12 Biology: Principles of Inheritance and Variation

Q159 neet_2026_03_may_morning Sex Determination in Honey Bee
In which animal do haploid cells divide mitotically to produce gametes?
  • A. Male honeybees
  • B. Male grasshoppers
  • C. Male earthworms
  • D. Male frogs

Solution

Core Logic

The male honeybee is haploid and females are diploid. The gamete formation in female honey bee is by meiosis, whereas male honeybees form gametes by mitosis. Thus, a haploid cell undergoes mitosis to produce gametes in male honeybees.

Pattern Recognition

Haplodiploid sex-determination system: Males (drones) develop parthenogenetically and are haploid. Therefore, they must produce sperm via mitosis to maintain the haploid state.

Chapter Mix

Class 12 Biology: Principles of Inheritance and Variation

More Principles of Inheritance and Variation Questions — neet_2026_03_may_morning

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JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%) | JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%)