Class 12th

DNA degrades quickly after an animal dies, so researchers once believed it impossible to find ancient genetic material. The search for primeval vestiges of DNA took off in the late 1980s after the development of a technique called polymerase chain reaction (PCR), which copies minute quantities of DNA. Armed with PCR, scientists could look for tiny fragments of DNA that might have weathered the millennia unharmed.

In recent years, researchers have isolated DNA from 20-million-year-old magnolia leaves and extracted DNA from a 135-million-year-old weevil found in amber. Recently, a team extract DNA from bone dating back millions of years for the first time. In the frenzied hunt for ancient DNA, microbiologist Scott R. Woodward may have bagged the biggest quarry. Drawing on lessons learned while growing up among the fossil-rich rocks of eastern Utah, Woodward and his team became the first people to find genetic material belonging to a dinosaur.

Woodward, whose grandfather was a coal miner, knew that mines in the area often contained dinosaur traces. After six months of looking Woodward pulled two bone fragments from a Cretaceous siltstone layer directly atop a coal seam. Impeded by an unstable mine roof, Woodward's team could not recover any more bone samples. The siltstone apparently inhibited fossilization and preserved much of the original cell structure in the bone. Researchers isolated strands of DNA from both fragments and used PCR to copy a segment that codes for a protein called cytochrome b. Once they had made many copies, they could determine the DNA sequence.

Throughout their work, the biologists took precautions to avoid contaminating the samples with modern DNA or ancient material found within the coal. According to Woodward, circumstantial evidence indicates that the bone fragments belong to one or two species of dinosaurs. Dinosaur tracks are abundant in this coal formation, and the bones visible in the mine were larger than those of a crocodile—the biggest non-dinosaur known in these rocks.

Woodward explains variation found in the DNA as a result of damage to the ancient DNA, which caused the PCR technique to alter the original sequence. Scientists had hoped to use the DNA to resolve debate about the relationship among birds, dinosaurs, and other reptiles. But the cytochrome b fragments were too short to offer meaningful phylogenetic information, says Woodward. Utah's state paleontologist believes that the fragments found by Woodward could definitely be dinosaur in origin. Other researchers, however, question the identity of the DNA strands. Because the copies of the cytochrome b sequence varied considerably, they wonder whether the DNA comes from several organisms.

Based on the passage, Woodward was pointing on what circumstantial evidences?

The four sentences (labelled 1, 2, 3 and 4) below, when properly sequenced, would yield a coherent paragraph. Decide on the proper sequencing of the order of the sentences and choose the correct option.

1. What we really are comes to the fore only rarely and in some specific circumstances.
2. What we think of ourselves as is, often, what determines how we behave, and our behaviour, we believe, determines what others think of us.
3. However, what we really are is hidden from others, either because we deliberately hide it from others or because we are unaware of how we actually are.
4. Like when we are in a crisis or under tremendous pressure, or conversely, when we are in a position of power and authority

DNA degrades quickly after an animal dies, so researchers once believed it impossible to find ancient genetic material. The search for primeval vestiges of DNA took off in the late 1980s after the development of a technique called polymerase chain reaction (PCR), which copies minute quantities of DNA. Armed with PCR, scientists could look for tiny fragments of DNA that might have weathered the millennia unharmed.

In recent years, researchers have isolated DNA from 20-million-year-old magnolia leaves and extracted DNA from a 135-million-year-old weevil found in amber. Recently, a team extract DNA from bone dating back millions of years for the first time. In the frenzied hunt for ancient DNA, microbiologist Scott R. Woodward may have bagged the biggest quarry. Drawing on lessons learned while growing up among the fossil-rich rocks of eastern Utah, Woodward and his team became the first people to find genetic material belonging to a dinosaur.

Woodward, whose grandfather was a coal miner, knew that mines in the area often contained dinosaur traces. After six months of looking Woodward pulled two bone fragments from a Cretaceous siltstone layer directly atop a coal seam. Impeded by an unstable mine roof, Woodward's team could not recover any more bone samples. The siltstone apparently inhibited fossilization and preserved much of the original cell structure in the bone. Researchers isolated strands of DNA from both fragments and used PCR to copy a segment that codes for a protein called cytochrome b. Once they had made many copies, they could determine the DNA sequence.

Throughout their work, the biologists took precautions to avoid contaminating the samples with modern DNA or ancient material found within the coal. According to Woodward, circumstantial evidence indicates that the bone fragments belong to one or two species of dinosaurs. Dinosaur tracks are abundant in this coal formation, and the bones visible in the mine were larger than those of a crocodile—the biggest non-dinosaur known in these rocks.

Woodward explains variation found in the DNA as a result of damage to the ancient DNA, which caused the PCR technique to alter the original sequence. Scientists had hoped to use the DNA to resolve debate about the relationship among birds, dinosaurs, and other reptiles. But the cytochrome b fragments were too short to offer meaningful phylogenetic information, says Woodward. Utah's state paleontologist believes that the fragments found by Woodward could definitely be dinosaur in origin. Other researchers, however, question the identity of the DNA strands. Because the copies of the cytochrome b sequence varied considerably, they wonder whether the DNA comes from several organisms.

All of the following, IF TRUE, would strengthen the author's claims EXCEPT

Direction: The passage below is accompanied by a set of questions. Choose the best answer to each question.

DNA degrades quickly after an animal dies, so researchers once believed it impossible to find ancient genetic material. The search for primeval vestiges of DNA took off in the late 1980s after the development of a technique called polymerase chain reaction (PCR), which copies minute quantities of DNA. Armed with PCR, scientists could look for tiny fragments of DNA that might have weathered the millennia unharmed.

In recent years, researchers have isolated DNA from 20-million-year-old magnolia leaves and extracted DNA from a 135-million-year-old weevil found in amber. Recently, a team extract DNA from bone dating back millions of years for the first time. In the frenzied hunt for ancient DNA, microbiologist Scott R. Woodward may have bagged the biggest quarry. Drawing on lessons learned while growing up among the fossil-rich rocks of eastern Utah, Woodward and his team became the first people to find genetic material belonging to a dinosaur.

Woodward, whose grandfather was a coal miner, knew that mines in the area often contained dinosaur traces. After six months of looking Woodward pulled two bone fragments from a Cretaceous siltstone layer directly atop a coal seam. Impeded by an unstable mine roof, Woodward's team could not recover any more bone samples. The siltstone apparently inhibited fossilization and preserved much of the original cell structure in the bone. Researchers isolated strands of DNA from both fragments and used PCR to copy a segment that codes for a protein called cytochrome b. Once they had made many copies, they could determine the DNA sequence.

Throughout their work, the biologists took precautions to avoid contaminating the samples with modern DNA or ancient material found within the coal. According to Woodward, circumstantial evidence indicates that the bone fragments belong to one or two species of dinosaurs. Dinosaur tracks are abundant in this coal formation, and the bones visible in the mine were larger than those of a crocodile—the biggest non-dinosaur known in these rocks.

Woodward explains variation found in the DNA as a result of damage to the ancient DNA, which caused the PCR technique to alter the original sequence. Scientists had hoped to use the DNA to resolve debate about the relationship among birds, dinosaurs, and other reptiles. But the cytochrome b fragments were too short to offer meaningful phylogenetic information, says Woodward. Utah's state paleontologist believes that the fragments found by Woodward could definitely be dinosaur in origin. Other researchers, however, question the identity of the DNA strands. Because the copies of the cytochrome b sequence varied considerably, they wonder whether the DNA comes from several organisms.

According to the passage, which myth was surpassed by the researchers later in the 1980s?