Whose experiments cracked the DNA and discobered unequivocally that a genetic code is a "triplet" :-

Options

A. Morgan ad Sturtevant
B. Beadly and Tatum
C. Nirenberg and Mathaei
D. Hershey and Chase

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the scientist(s) whose experiments led to the discovery that the genetic code is a triplet.

2. **Identifying Key Terms**: The term "triplet" refers to the codon, which is a sequence of three nucleotides in DNA or RNA that codes for a specific amino acid.

3. **Historical Context**: The discovery regarding the triplet nature of the genetic code was made in the early 1960s.

4. **Key Scientists**: The primary scientists credited with this discovery are Marshall Nirenberg and Heinrich Matthaei.

5. **Experimental Setup**: Nirenberg and Matthaei conducted their experiments using a cell-free system. This means they were able to synthesize proteins without using living cells.

6. **Use of Polyuracil RNA**: They used a synthetic RNA composed entirely of uracil (polyuracil RNA) for their experiments. In RNA, uracil replaces thymine, which is found in DNA.

7. **Results of the Experiment**: Upon translating the polyuracil RNA, they found that the resulting polypeptide consisted solely of the amino acid phenylalanine.

8. **Conclusion**: From their findings, they concluded that the triplet codon "UUU" corresponds to the amino acid phenylalanine, thus establishing that the genetic code is indeed a triplet.

### Final Answer:
The experiments that cracked the DNA and discovered unequivocally that the genetic code is a triplet were conducted by Marshall Nirenberg and Heinrich Matthaei in 1961.

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