Usually, how many nucleotides are found in a tRNA molecule?

[Molecular-Basis-of-Inheritance] [class-xii ]

• 70-90
• 100-200
• 300-500
• Thousands
Correct Option: A  [ 70-90 ]

Remark: tRNA molecules are relatively small, typically consisting of about 73 to 93 nucleotides. This compact size allows them to fit into the ribosome during translation.

During DNA replication, the primers are chemically?

[Molecular-Basis-of-Inheritance] [class-xii ]

• DNA
• RNA
• Protein
• Lipid
Correct Option: B  [ RNA ]

Remark: The primers used to initiate DNA synthesis in vivo are short strands of RNA synthesized by the enzyme Primase. They provide the free 3-prime hydroxyl group needed by DNA polymerase.

The unwinding of DNA creates a Y-shaped structure called?

[Molecular-Basis-of-Inheritance] [class-xii ]

• Replication bubble
• Replication fork
• Origin
• Okazaki fragment
Correct Option: B  [ Replication fork ]

Remark: The separation of the two DNA strands creates a Y-shaped region where the helix is being unwound and new strands are being synthesized. This structure is called the replication fork.

Which of the following is a non-sense codon?

[Molecular-Basis-of-Inheritance] [class-xii ]

• AUG
• UGC
• UGA
• UGG
Correct Option: C  [ UGA ]

Remark: Non-sense codons are stop codons that do not code for any amino acid. UGA (Opal) is one of the three stop codons.

In which organisms are transcription and translation not coupled?

[Molecular-Basis-of-Inheritance] [class-xii ]

• Bacteria
• Eukaryotes
• E. coli
• Cyanobacteria
Correct Option: B  [ Eukaryotes ]

Remark: In eukaryotes, transcription occurs in the nucleus, and translation occurs in the cytoplasm. The physical separation by the nuclear envelope prevents coupling. In prokaryotes, they happen in the same compartment simultaneously.

The cap added to the 5-prime end of eukaryotic mRNA is composed of?

[Molecular-Basis-of-Inheritance] [class-xii ]

• Poly-A
• 7-methylguanosine
• Methylated Adenine
• Phosphated Cytosine
Correct Option: B  [ 7-methylguanosine ]

Remark: The 5-prime cap is a modified guanine nucleotide, specifically 7-methylguanosine, attached via a unique 5-to-5 triphosphate linkage.

Which scientist proposed the "One gene, One enzyme" hypothesis (related concept)?

[Molecular-Basis-of-Inheritance] [class-xii ]

• Beadle and Tatum
• Watson and Crick
• Jacob and Monod
• Hershey and Chase
Correct Option: A  [ Beadle and Tatum ]

Remark: Although usually taught in broader genetics, Beadle and Tatum proposed "One gene, One enzyme" (later one gene, one polypeptide), linking genes to protein function.

Jacob and Monod are famous for elucidating?

[Molecular-Basis-of-Inheritance] [class-xii ]

• Structure of DNA
• Genetic Code
• Lac Operon
• DNA replication
Correct Option: C  [ Lac Operon ]

Remark: Francois Jacob (a geneticist) and Jacques Monod (a biochemist) were the first to elucidate the transcriptional regulation system known as the Lac Operon.

In the absence of lactose, the repressor binds to the?

[Molecular-Basis-of-Inheritance] [class-xii ]

• Promoter
• Structural gene
• Operator
• Inducer
Correct Option: C  [ Operator ]

Remark: When lactose is absent, the repressor protein remains active and binds tightly to the operator region of the operon, physically blocking RNA polymerase from transcribing the structural genes.

Which human chromosome was the last to be sequenced?

[Molecular-Basis-of-Inheritance] [class-xii ]

• Chromosome X
• Chromosome Y
• Chromosome 1
• Chromosome 22
Correct Option: C  [ Chromosome 1 ]

Remark: Chromosome 1 is the largest human chromosome and was the last one to be completely sequenced, with the sequence published in May 2006.