The correct answer is option 1, which states that the discovery of DNA structure by James D Watson and Francis Crick occurred first. This groundbreaking discovery took place in 1953, where Watson and Crick proposed the double helix structure of DNA. This discovery was crucial in understanding the genetic code and has had a significant impact on various fields such as medicine, biology, and genetics.
Option 2 states that Yuri Gagarin became the first man in space. This event occurred on April 12, 1961, and is significant as Gagarin`s spaceflight marked the beginning of human space exploration.
Option 3 mentions the world`s first human heart transplant, performed by Dr. Christian Barnard. This historic medical breakthrough took place on December 3, 1967, in South Africa.
Option 4 refers to the birth of the world`s first test tube baby, Louise Brown, in the United Kingdom. This event occurred on July 25, 1978 and was a significant milestone in reproductive medicine.
In summary, while the correct answer is option 1, it is important to note the chronological order of the other notable events mentioned.