Molecular Basis of Inheritance Previous Year Questions — NEET Biology
4 past-year Molecular Basis of Inheritance questions from NEET (Biology).
Q104 (2024)
Which of the following statements are correct with reference to a transcription unit?
A. A transcription unit in DNA is defined primarily by three regions : promoter, structural gene and terminator.
B. The promoter is said to be located towards the 5'-end of the structural gene.
C. The promoter is a DNA sequence that provides binding site for RNA polymerase.
D. The promoter defines the template and coding strands.
E. The terminator is located towards the 3'-end of the coding strand and it defines the end of the process of transcription.
Choose the correct answer from the options given below:
- A, B, C, D and E
- B, C, D and E only
- A, C, D and E only
- A, B, C and D only
### Related Formula
Transcription Unit: Promoter (5'-end of coding strand) + Structural Gene + Terminator (3'-end of coding strand).
### Core Logic
- A: A transcription unit consists of promoter, structural gene, and terminator (True).
- B: Promoter is at the 5'-end (upstream) relative to coding strand (True).
- C: Promoter binds RNA polymerase (True).
- D: Presence and orientation of promoter defines template vs coding strand (True).
- E: Terminator is at 3'-end of coding strand and signals end of transcription (True).
### Step 1: Conclusion
All statements A, B, C, D, and E are correct. Option (1) is correct.
### Pattern Recognition
Every listed statement (A-E) is a verbatim accurate definition of a transcription unit from NCERT.
### Evaluation Rubric / Model Answer
null
### Chapter Mix
Class 12 Biology: Molecular Basis of Inheritance
Q116 (2024)
Arrange the following steps of DNA fingerprinting in a correct sequence.
A. Isolation of DNA and its digestion by restriction endonucleases.
B. Hybridisation using a labelled VNTR probe.
C. Transferring of separated DNA fragments to synthetic membranes.
D. Detection of hybridised DNA fragments by autoradiography.
E. Separation of DNA fragments by electrophoresis.
Choose the correct answer from the options given below:
- A, E, C, B, D
- A, E, B, C, D
- A, B, D, C, E
- A, D, B, E, C
### Related Formula
DNA Fingerprinting Workflow:
Isolation & Digestion $\rightarrow$ Gel Electrophoresis $\rightarrow$ Southern Blotting (Transfer) $\rightarrow$ Hybridization with Probe $\rightarrow$ Autoradiography.
### Core Logic
Sequence of steps:
1. Isolation and digestion of DNA by restriction enzymes (A)
2. Separation of fragments by gel electrophoresis (E)
3. Transferring (blotting) to synthetic membrane (C)
4. Hybridisation using labelled VNTR probe (B)
5. Detection by autoradiography (D)
### Step 1: Conclusion
The correct order is A $\rightarrow$ E $\rightarrow$ C $\rightarrow$ B $\rightarrow$ D. Correct option is (1).
### Pattern Recognition
Blotting (C) must happen BEFORE hybridization (B), and autoradiography (D) is the final detection step. Order: A, E, C, B, D.
### Evaluation Rubric / Model Answer
null
### Chapter Mix
Class 12 Biology: Molecular Basis of Inheritance
Q123 (2024)
Which of the following statements are correct with reference to packaging of DNA helix?
A. Histones are organized to form a unit of eight molecules called histone octamer.
B. Histones are negatively charged basic proteins.
C. Histones are rich in the basic amino acid residues - lysine and arginine.
D. The positively charged DNA is wrapped around the histone octamer to form nucleosome.
E. The packaging of chromatin at higher levels requires an additional set of proteins called non-histone chromosomal proteins.
Choose the correct answer from the options given below :
- A, B and D only
- A, C and E only
- C, D and E only
- B, D and E only
### Related Formula
Histones: Positively charged, basic proteins (rich in Lysine and Arginine).
DNA: Negatively charged (due to phosphate groups).
### Core Logic
- A: Histones form an 8-molecule unit (histone octamer) (True).
- B: Histones are POSITIVELY charged basic proteins, not negatively charged (False).
- C: Histones are rich in lysine and arginine (True).
- D: DNA is NEGATIVELY charged, not positively charged (False).
- E: Higher-level chromatin packing requires NHC (Non-Histone Chromosomal) proteins (True).
### Step 1: Selection
Correct statements are A, C, and E. Option (2) is correct.
### Pattern Recognition
Histones = Positively charged; DNA = Negatively charged. Spotting charge inversion in B and D eliminates 1, 3, 4.
### Evaluation Rubric / Model Answer
null
### Chapter Mix
Class 12 Biology: Molecular Basis of Inheritance
Q125 (2024)
In the lac operon, the z gene codes for
- transacetylase
- the repressor of lac operon
- permease
- beta-galactosidase
### Related Formula
Lac Operon Genes:
$i$ gene $\rightarrow$ Repressor protein
$z$ gene $\rightarrow \beta$-galactosidase
$y$ gene $\rightarrow$ Permease
$a$ gene $\rightarrow$ Transacetylase
### Core Logic
In the *lac* operon of *E. coli*, structural gene *z* codes for $\beta$-galactosidase enzyme, which hydrolyzes lactose into glucose and galactose.
### Step 1: Selection
The z gene codes for beta-galactosidase. Option (4) is correct.
### Pattern Recognition
Lac Operon: z = $\beta$-galactosidase, y = permease, a = transacetylase.
### Evaluation Rubric / Model Answer
null
### Chapter Mix
Class 12 Biology: Molecular Basis of Inheritance
