The main phospholipids in most animal cell membranes are the | Agrigyan

• Sequence-Specific Protein-DNA Interactions:
• DNA-binding proteins (transcription factors, repressors, zinc fingers, helix-turn-helix, leucine zippers) recognize and bind specific DNA target motifs without melting the double helix.
• They achieve this by inserting $\alpha$-helical recognition motifs into the major and minor grooves of the B-DNA double helix, where the functional hydrogen-bond donors, acceptors, and methyl groups of individual base pairs are exposed in unique geometrical patterns.
• nalysis:
• (interacting with the bases in the major and minor grooves of the double helix): Correct.

Correct option: (4) interacting with the bases in the major and minor grooves of the double helix.

• Analysis of Carbohydrate and Nucleotide Subunits:
• Statement 1: Glycogen is a branched polymer of $\alpha$-D-glucose units. (Correct).
• Statement 2: Cellulose is an unbranched polymer of $\beta$-D-glucose units. (Correct).
• Statement 3: "Lactose is formed from units that include ribose" (Incorrect / False):
• Lactose is a disaccharide formed by $\beta(1\rightarrow 4)$-linked D-galactose and D-glucose, containing zero ribose.
• Statement 4: Adenosine is a purine nucleoside formed from adenine and D-ribose. (Correct).
• nalysis:
• Statement 3 is incorrect, hence the correct answer.

• Cellular Differentiation:
• The developmental process whereby a generic, unspecialized stem or progenitor cell undergoes selective, coordinated gene expression changes to develop stable morphological and biochemical attributes, adopting a specialized physiological role (e.g., neuron, hepatocyte, cardiomyocyte, erythrocyte).
• nalysis:
• (adoption of a specialized physiological role by a cell): Correct definition.

Correct option: (4) adoption of a specialized physiological role by a cell