b. What conclusions did Watson and Crick reach after seeing this imageand reading Franklin’s report discussing the symmetry of DNA?

After seeing the image and reading Franklin's report discussing the symmetry of DNA, Watson and Crick reached several important conclusions that led to their proposal of the double helix model of DNA.

1. They concluded that DNA was a double-stranded molecule. This was based on the X-shaped pattern of the image, which suggested a helical structure with two strands.

2. They inferred that the two strands of DNA were antiparallel, meaning they ran in opposite directions. This was based on the symmetry of the DNA molecule that Franklin had reported.

3. They concluded that the bases (adenine, thymine, guanine, and cytosine) were paired in a specific way. This was based on the uniform width of the DNA molecule suggested by the image, which implied that a large purine base (adenine or guanine) was always paired with a smaller pyrimidine base (thymine or cytosine).

4. They proposed that the base pairs were held together by hydrogen bonds, which could be easily broken and reformed during DNA replication. This was based on the known chemistry of the bases and the need for a mechanism that could explain how DNA could be copied.

5. Finally, they concluded that the sequence of bases along the DNA strand carried the genetic information. This was based on the understanding that the sequence of bases could vary between different DNA molecules, providing a way to encode different genetic instructions.