What is the significance of the START codon AUG in the genetic code?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• It codes for the amino acid Valine only.
• It acts as the only STOP signal for translation.
• It codes for Methionine (Met) and initiates translation.
• It codes for the amino acid Glutamic acid.
Correct Option: C  [ It codes for Methionine (Met) and initiates translation. ]

Remark: AUG is the most common start codon, which always codes for the amino acid Methionine and signals the ribosome to begin protein synthesis.

The three-nucleotide sequence on the tRNA that recognizes the codon on the mRNA is the:

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Triplet
• Codon
• Allele
• Anticodon
Correct Option: D  [ Anticodon ]

Remark: The anticodon on the tRNA is complementary to the codon on the mRNA, ensuring that the correct amino acid is incorporated into the growing polypeptide chain.

Which scientist, listed in the unit introduction, is known for co-discovering the double helix structure of DNA?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Khorana
• Monod
• James Watson
• Benzer
Correct Option: C  [ James Watson ]

Remark: James Watson and Francis Crick are famously credited with elucidating the double helix structure of DNA in 1953.

Which molecular process is essential for providing genetic stability and transmitting genetic information accurately to the next generation?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Transcription
• Translation
• DNA Replication
• Splicing
Correct Option: C  [ DNA Replication ]

Remark: DNA replication, the process of making identical copies of the DNA, is essential for ensuring that each daughter cell or offspring receives a complete and stable set of genetic instructions.

What was the major contribution of T.H. Morgan in the field of genetics?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Proving that DNA is the genetic material.
• Postulating the Law of Segregation.
• Proving the chromosomal theory of inheritance using Drosophila.
• Co-discovering the structure of DNA.
Correct Option: C  [ Proving the chromosomal theory of inheritance using Drosophila ]

Remark: T.H. Morgan's experiments on the fruit fly (Drosophila melanogaster), particularly with sex-linked traits like eye color, provided concrete evidence that genes are located on chromosomes, confirming the Chromosomal Theory of Inheritance.

The organism T.H. Morgan primarily worked with to establish the chromosomal theory of inheritance was:

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Garden pea (Pisum sativum)
• Fruit fly (Drosophila melanogaster)
• Neurospora
• E. coli
Correct Option: B  [ Fruit fly (Drosophila melanogaster) ]

Remark: Drosophila melanogaster (fruit fly) was Morgan's model organism due to its short life cycle, high number of progeny, and clearly distinguishable inherited traits.

Which scientist worked alongside James Watson to propose the model of the DNA double helix?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Khorana
• Nirenberg
• Francis Crick
• T.H. Morgan
Correct Option: C  [ Francis Crick ]

Remark: James Watson and Francis Crick co-authored the 1953 paper describing the structure of DNA.

The 'entire body of molecular biology' was a consequent development following the understanding of the nature of Mendel’s factors, with major contributions from which group of scientists?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Mendel, Morgan, and Darwin
• Watson, Crick, Nirenberg, and Khorana
• Lamarck, Malthus, and Wallace
• Sutton, Boveri, and Hershey
Correct Option: B  [ Watson, Crick, Nirenberg, and Khorana ]

Remark: The text specifically lists "Watson, Crick, Nirenberg, Khorana, Kornbergs (father and son), Benzer, Monod, Brenner" as major contributors to the development of molecular biology.

Which scientist is known for his work in chemically synthesizing genetic code words, contributing significantly to cracking the genetic code?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• James Watson
• Francis Crick
• H. G. Khorana
• T.H. Morgan
Correct Option: C  [ H. G. Khorana ]

Remark: H. G. Khorana developed chemical methods to synthesize long nucleotide sequences, which was crucial in determining the codons for specific amino acids.

Which of the following is NOT considered a fundamental mechanism of evolution?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Mutation
• Genetic Drift
• Natural Selection
• Inheritance of Acquired Characteristics
Correct Option: D  [ Inheritance of Acquired Characteristics ]

Remark: The inheritance of acquired characteristics (Lamarckism) is a discredited theory. Mutation, Genetic Drift, and Natural Selection are the modern accepted mechanisms of evolution.