If the four bases of DNA have to code for twenty amino acids, the code should constitute a combination of bases. This was proposed by

Options

A. Rosalind
B. Har Gobind Khorana
C. George Gamow
D. Marshall Nirenberg

Answer

To answer the question, "If the four bases of DNA have to code for twenty amino acids, the code should constitute a combination of bases. This was proposed by," we need to analyze the contributions of various scientists mentioned in the video transcript.

### Step-by-Step Solution:

1. **Understanding the Problem**: We need to identify which scientist proposed the idea that combinations of the four DNA bases (adenine, guanine, thymine, and cytosine) could code for the twenty amino acids.

2. **Identifying Key Scientists**:
- **Rosalind Franklin**: Known for her work on the structure of DNA using X-ray crystallography. She did not propose the coding system for amino acids.
- **George Gamow**: He is credited with proposing that the genetic code is based on combinations of the four bases. He suggested that a combination of three bases (a triplet) could code for an amino acid.
- **Marshall Nirenberg**: He worked on deciphering the genetic code and was involved in the triplet codon concept, but he did not originate the idea of combinations coding for amino acids.
- **Har Gobind Khorana**: He contributed to the understanding of the genetic code and helped in the elucidation of how the triplet codons correspond to amino acids.

3. **Conclusion**: The correct answer to the question is **George Gamow**, as he was the one who proposed the concept of using combinations of the four bases to code for amino acids.

### Final Answer:
The idea that combinations of the four bases of DNA can code for twenty amino acids was proposed by **George Gamow**.

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