DNA structure and replication
Why this is asked: Meselson and Stahl's density-gradient experiment on E. coli, tracking 15N and 14N through generations, is the direct proof that replication is semiconservative — each new DNA molecule keeps exactly one parental strand — and NEET likes to ask which generation produces which density band.
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- •Histones are enriched with:
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Given below are two statements:
Statement I: In the RNA world, RNA is considered the first genetic material, evolved to carry out essential life processes. RNA acts as a genetic material and also as a catalyst for some important biochemical reactions in living systems. Being reactive, RNA is unstable.
Statement II: DNA evolved from RNA and is a more stable genetic material. Its double-helical strands, being complementary, resist changes by evolving a repairing mechanism.
In the light of the above statements, choose the most appropriate answer from the options given below:
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Match List I with List II.
List I List II A. Alfred Hershey and Martha Chase I. Streptococcus pneumoniae B. Euchromatin II. Densely packed and dark-stained C. Frederick Griffith III. Loosely packed and light-stained D. Heterochromatin IV. Confirmation of DNA as genetic material Choose the correct answer from the options given below:
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