سؤال قراءة ستيب محلول — فهم التفاصيل (تدريب 7238)

Passage A: The Importance of DNA How did the discovery of DNA Impact the Scientific Community? (1)From the time DNA was first identified as a distinct molecule within cells, our understanding of DNA has grown as members of the scientific community have built upon each other’s finding through farther experiments. The discovery of DNA focused scientists’ efforts and led to the research into genetics and heredity aimed at improving life on Earth today. Identification of DNA (2)DNA’s discovery can be traced to 1868, when Swiss medical student Johann Friedrich Miescher began work on isolating proteins from white blood cells. Miescher found a substance that contained more phosphorus than cellular proteins and could not be broken down as proteins could. His discovery of what he called “nuclein” proved an important key for scientists decades later who were trying to determine which chemical components of cells carried genetic information. Investigation into DNA’s Function and Structure (3)In the 1940s. American biologist Oswald Avery and colleagues at Rockefeller University exposed one type of pneumonia bacteria to the DNA from another type without any proteins present, transforming the first type into the second and demonstrating that DNA was the agent of change. A decade later, James Watson and Francis Crick of Cambridge University suggested that DNA carried information in a code that aided in protein synthesis and existed as a double-stranded molecule, or double helix, structure, that carried the instructions for copying itself and transferring genetic material across generations. Application to a Broad Range of Fields (4)Today, our understanding of DNA’s role and structure guides procedures and research in fields from agriculture to law. The ability to identify specific genes has assisted plant breeders in producing crops with hardy, desirable traits that result from the proteins DNA helps create. Meanwhile, analysis of the 1 percent of DNA sequences that vary among human beings has been useful in identifying persons of interest from biological evidence found at the scenes of violent crimes Integration into Medical Research (5) Experiments with DNA have probably had the greatest impact on medicine, especially in developing drugs and identifying and treating cancer. In 2013, researchers at Queen Mary University in London announced chemical “tags” on DNA sequences that seemed to coincide with occurrences of head and neck cancers, suggesting these cancers could be predicted. Coupling these tests with gene therapy - the alteration of genes known to play roles in cancer - could create a legacy unimaginable when DNA was first discovered. Passage B: The discovery of DNA (1)It is a common misconception that James Watson and Francis Crick discovered DNA in the 1950s. In reality, DNA was discovered decades before. It was by following the work of the pioneers before them that James and Francis were able to come to their ground-breaking conclusion about the structure of DNA in 1953. The story of the discovery of DNA begins in the 1800s… The molecule of life (2)The molecule now known as DNA was first identified in the 1860s during research into the key components of white blood cells, part of our body’s immune system. The main source of these cells was pus-coated bandages collected from a nearby medical clinic. (3)Researchers carried out experiments using salt solutions to understand more about what makes up white blood cells. They noticed that, when they added acid to a solution of the cells, a substance separated from the solution. This substance then dissolved again when an alkali was added. When investigating this substance, they realized that it had unexpected properties different to those of the other proteins they were familiar with. They called this mysterious substance “nuclein”, because they believed it had come from the cell nucleus. The four building blocks of DNA (4)Albrecht Kossel was a German biochemist who made great progress in understanding the basic building blocks of nuclein. (5)In 1881 Albrecht identified nuclein as a nucleic acid and provided its present chemical name, deoxyribonucleic acid (DNA). This work was rewarded in 1910 when he received the Nobel Prize in Physiology or Medicine. Disease Diagnosis and Treatment (6)As noted, one important area of DNA research is that of genetics and medical research. Due to our discovery of DNA, our ability to actually diagnose diseases early on has been vastly improved. In addition, we have been able to better assess a person’s genetic susceptibility to specific diseases. In doing so, we have also paved the pathway to formulate brand new drugs to treat these diseases. In fact, drugs can essentially be custom made to complement a person’s personal biochemistry and genetic makeup. (7) The impact of DNA on agriculture has been a very important one because it has allowed breeders to facilitate the breeding of animals that have a better resistance to diseases. It also allows farmers to produce more nutritious produce. What can we understand from passage A and B about the discovery of DNA?