NEET · Biology —

Principles of Inheritance and Variation appeared 7 times across 1 year — 7.8% of Biology. This question is from Gene Mutations and Sickle-Cell Anaemia.

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

Related Formula

Normal codon (GAG) Point mutation (A arrow U) Mutant codon (GUG) arrow Valine (Val)

Core Logic

Sickle-cell anaemia is caused by a point mutation in the beta-globin gene. The normal 6th codon GAG is mutated to GUG in mRNA. This leads to the substitution of Glutamic acid (Glu) by Valine (Val) at the 6th position of the beta-globin polypeptide chain, causing polymerisation under low oxygen tension and distorting RBCs into a sickle shape.

Step 1: Identification of Mutant Codon

The normal codon is GAG and the mutant codon is GUG.

Pattern Recognition

Sees: "sixth mutant codon beta globin gene". Shortcut: Normal = GAG (Glutamic acid), Mutant = GUG (Valine).

Chapter Mix

Class 12 Biology: Principles of Inheritance and Variation

Reference Study Guides

Principles Of Inheritance And Variation

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

Q154 neet_2024_05_may_morning Sex Determination in Grasshopper (XX-XO Type)
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

Related Formula

Grasshopper Sex Determination (XX-XO): aligned Male &= 22 Autosomes + X = 23 chromosomes (XO) Female &= 22 Autosomes + XX = 24 chromosomes (XX) aligned

Core Logic

In grasshoppers, sex determination is of the XX-XO type. Males have only one X chromosome in addition to autosomes (XO), giving them an odd total chromosome number (23). Females have a pair of X chromosomes (XX), giving them an even total chromosome number (24).

Step 1: Match

23 chromosomes = males; 24 chromosomes = females.

Pattern Recognition

Sees: "grasshopper 23 and 24 chromosomes". Shortcut: XX-XO type arrow XO male has 1 less chromosome (23) than XX female (24).

Chapter Mix

Class 12 Biology: Principles of Inheritance and Variation

Q159 neet_2024_05_may_morning Gametogenesis in Haploid Organisms
In which animal do haploid cells divide mitotically to produce gametes?
  • A. Male honeybees
  • B. Male grasshoppers
  • C. Male earthworms
  • D. Male frogs

Solution

Related Formula

Haplodiploidy in Honeybees: Male (Drone, n = 16) Mitosis Sperm ( n = 16)

Core Logic

Male honeybees (drones) develop parthenogenetically from unfertilised haploid eggs (n = 16). Because their body cells are already haploid, they produce gametes (sperms) via mitosis rather than meiosis.

Step 1: Evaluation of Other Options

Male grasshoppers, earthworms, and frogs are diploid organisms (2n) and produce gametes through meiotic division.

Pattern Recognition

Sees: "haploid cells divide mitotically to produce gametes". Shortcut: Male honeybees (drones).

Chapter Mix

Class 12 Biology: Principles of Inheritance and Variation

More Principles of Inheritance and Variation Questions — neet_2024_05_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%)