What major discovery regarding DNA was made in 1953?

The major discovery about DNA made in 1953 was the identification of its structure as a double helix. This groundbreaking finding was primarily attributed to the work of James Watson and Francis Crick, who built upon the findings of previous researchers, including Rosalind Franklin, whose x-ray diffraction images of DNA were crucial to understanding its helical structure.

The double helix model proposed that DNA consists of two strands wound around each other, with the strands composed of nucleotide units featuring a sugar, phosphate, and a nitrogenous base. This structure explained how DNA could replicate and how genetic information could be stored and transmitted across generations. The understanding of DNA’s double helix configuration laid the foundation for further genetic research and advancements in molecular biology, such as understanding how genes are expressed and regulated.

The other options present incorrect assertions about DNA. For instance, DNA is not a single helix structure, it is not strictly RNA, and, while significant progress was being made regarding understanding the genetic code, it was not fully deciphered in 1953.