الحمض النووي قطعة قراءة ستيب رقم 1

نص القطعة

Passage A (1) In 1869 the Swiss scientist Friedrich Miescher, working in Tübingen, Germany, isolated a strange substance from the nuclei of white-blood cells. Thatevent marked the first time DNA was identified as its own molecule in Germany and launched the study of genetics. (2) Miescher called the material nuclein. Later work showed that nuclein is the main ingredient of DNA, built from a sugar-phosphate backbone and four bases that store information. (3) By the mid-1900s, understanding DNA’s code helped doctors fight inherited illnesses and let plant breeders raise healthier crops, proving that knowledge of genes could aid both medicine and farming. Pioneers even imagined tailoring future drugs to each patient’s genes. (4) These ideas linked tiny molecules to the visible traits of every living thing, preparing the ground for the next breakthroughs. Passage B (5) Decades after its first identification as a molecule in Germany, James Watson and Francis Crick revealed DNA’s double-helix structure in 1953, showing how genetic codes copy themselves. (6) Biologists confirmed that the long-studied nucleintruly forms the core of DNA in every species, explaining its stability and power to pass traits on. (7) With this insight, researchers engineered disease-resistant wheat and developed gene tests that guide precise medical treatments, again linking medicine and farming through the same molecule. (8) Today, reading an individual genome lets doctors design medicines specifically for that person, a practice called personalised medicine, and gene editing promises even more targeted care.