Class 12 Biology Important Chapter 6 Molecular Basis of Inheritances

Class 12 Biology Important Chapter 6 Molecular Basis of Inheritances Solutions English Medium As Per The New Syllabus to each chapter is provided in the list so that you can easily browse through different chapters ASSEB Class 12 Biology Important Solutions in English and select need one. AHSEC Class 12 Biology Additional Notes Download PDF. HS 2nd Year Biology Additional Solutions.

Class 12 Biology Important Chapter 6 Molecular Basis of Inheritances

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Molecular Basis of Inheritances

Chapter: 6

IMPORTANT QUESTION AND ANSWER

Answer the Following Question:

1. What are purines and pyrimidines? Give examples.

Ans: Purines are nitrogenous bases with a double-ring structure. 

Examples: Adenine (A) and Guanine (G).

Pyrimidines are nitrogenous bases with a single-ring structure. 

Examples: Cytosine (C), Thymine (T) (in DNA), and Uracil (U) (in RNA).

2. State Chargaff’s rule.

Ans: Chargaff’s rule states that in a DNA molecule, the amount of adenine equals thymine and the amount of guanine equals cytosine. That is, A = T and G = C.

3. Name the enzyme that removes RNA primers during DNA replication.

Ans: DNA polymerase I removes the RNA primers and replaces them with DNA nucleotides.

4. What is a codon?

Ans: A codon is a triplet sequence of nucleotides on mRNA that codes for a specific amino acid or a stop signal during protein synthesis.

5. What is the function of tRNA in translation?

Ans: tRNA (transfer RNA) carries specific amino acids to the ribosome and pairs with the codon on the mRNA using its anticodon, thus facilitating protein synthesis.

6. How does DNA differ from RNA?

Ans: (i) DNA is double-stranded, RNA is single-stranded.

(ii) DNA contains deoxyribose, RNA contains ribose.

(iii) DNA has thymine (T), RNA has uracil (U) instead.

7. What are VNTRs and how are they useful?

Ans: VNTRs (Variable Number Tandem Repeats) are short DNA sequences repeated in tandem. They are highly variable among individuals and are used in DNA fingerprinting.

8. State one use of DNA fingerprinting.

Ans: DNA fingerprinting is used in criminal investigations, paternity testing, and identifying individuals.

9. What is DNA packaging? Explain how DNA is packaged in eukaryotes.

Ans: DNA packaging refers to the folding and coiling of DNA into compact structures so it can fit within the cell nucleus. In eukaryotes, DNA wraps around histone proteins to form nucleosomes. Nucleosomes coil to form chromatin, which further condenses to form chromosomes.

10. Explain the semiconservative nature of DNA replication.

Ans: The semiconservative model of DNA replication means that each new DNA molecule consists of one original (parental) strand and one newly synthesized strand. This was experimentally proven by Meselson and Stahl using nitrogen isotopes (¹⁵N and ¹⁴N) in E. coli.

11. What is the role of regulatory genes in the lac operon?

Ans: In the lac operon, the regulatory gene (lacI) codes for the repressor protein. In the absence of lactose, the repressor binds to the operator region, blocking transcription. When lactose is present, it acts as an inducer, inactivating the repressor and allowing gene transcription.

12. How does translation take place in a cell?

Ans: Translation occurs in the cytoplasm where ribosomes read the mRNA codons. tRNA molecules bring the correct amino acids, which are joined by peptide bonds to form a polypeptide chain. The process includes initiation, elongation, and termination.