The substance that gives skin its pigment and protects against UV radiation is:
A. Keratin
B. Collagen
C. Melanin
D. Elastin
Answer: Option C
Solution (By JKSSB Mock Tests)
Melanin, produced by melanocytes in the epidermis, is the primary pigment determining skin, hair, and eye color. It absorbs UV radiation, protecting DNA from damage. Keratin is a structural protein in hair and nails, collagen provides connective tissue strength, elastin elasticity. Albinism results from melanin deficiency.
Explanation:
Auxin (indole-3-acetic acid) produced at the shoot apex suppresses the growth of lateral buds, a phenomenon called apical dominance. Removing the apex allows lateral buds to grow. Cytokinin promotes cell division and counteracts apical dominance. Gibberellin stimulates stem elongation, and ethylene is involved in fruit ripening and senescence. The auxin-cytokinin ratio determines root and shoot differentiation in tissue culture.
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