What might Watson and Crick have concluded had Chargaff's data from a single source indicated the following? A T G C % 29 19 21 31 Why would this conclusion be contradictory to Wilkins's and Franklin's data?

Verified step by step guidance

1. Step 1: Understand Chargaff's rules, which state that in any given DNA sample, the amount of adenine (A) is approximately equal to thymine (T), and the amount of guanine (G) is approximately equal to cytosine (C).
2. Step 2: Analyze the given data: A = 29%, T = 19%, G = 21%, C = 31%. Notice that these percentages do not follow Chargaff's rules, as A is not equal to T, and G is not equal to C.
3. Step 3: Consider what Watson and Crick might conclude from this data. They might hypothesize that DNA does not have a consistent base pairing rule, or that the structure of DNA might be different from the double helix model they proposed.
4. Step 4: Recall Wilkins's and Franklin's data, which provided X-ray diffraction images suggesting a helical structure with consistent spacing, supporting the idea of specific base pairing.
5. Step 5: Recognize the contradiction: If Chargaff's data from a single source did not show equal A-T and G-C pairing, it would contradict the helical structure with specific base pairing suggested by Wilkins's and Franklin's data. This would challenge the double helix model.

Key Concepts

Chargaff's Rules

Chargaff's Rules state that in DNA, the amount of adenine (A) equals thymine (T), and the amount of guanine (G) equals cytosine (C). This base pairing is crucial for understanding the structure of DNA, as it suggests a complementary relationship between the bases, which is fundamental to the double helix model proposed by Watson and Crick.

DNA Structure

The structure of DNA is a double helix formed by two strands of nucleotides running in opposite directions, with complementary base pairing between A-T and G-C. This structural arrangement is essential for DNA replication and function, and any deviation from the expected base pairing ratios would challenge the validity of the double helix model.

Wilkins and Franklin's Data

Rosalind Franklin and Maurice Wilkins conducted X-ray diffraction studies that provided critical insights into the helical structure of DNA. Their data suggested a consistent pattern of base pairing and spacing, which would be contradicted if Chargaff's data indicated an unequal ratio of bases, undermining the proposed double helix model and the complementary nature of DNA.