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Blababa [14]
3 years ago
6

Sensitivity and specificity are important criteria for screening and diagnostic instruments. What is specificity?

Biology
1 answer:
Gwar [14]3 years ago
8 0

Answer:

specificity is an important criteria for screening and diagnostic instruments, the specificity of a test reflects the probability that the screening test will be negative among those who, in fact, do not have a disease.

A test that is 90% specific will identify 90% of patients who do not have the disease. Tests with a high specificity (a high true negative rate) are most useful when the result is positive. A highly specific test can be useful for ruling in patients who have a certain disease.

Explanation:

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zmey [24]

In Eukaryotes, the DNA replication can start at several sites or places in the DNA molecule or DNA strand. The only important factor for DNA replication to start is that it starts at replication fork.

The replication of DNA is semi-conservative in nature because each strand acts as a template for synthesizing a new complementary strand of the double helix.

The new DNA is made with the help of the enzyme DNA polymerase which requires a primer for starting the DNA synthesis.

Replication occurs only at specific regions of DNA known as origin of replication and these are short sequences of nucleotides which are recognized by the enzyme for the replication.

The special enzymes or proteins recognize the specific sites and then binds to them. After binding, the DNA is opened up forming the replication forks which are two Y- shaped structures.

6 0
3 years ago
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A molecule that can be used as a molecular clock has a neutral mutation rate of one mutation per 5 million years. How many years
gregori [183]

Answer:To put dates on events in evolutionary history, biologists count how many mutations have accumulated over time in a species’ genes. But these “molecular clocks” can be fickle. A paper in the 28 September Physical Review Letters mathematically relates erratic “ticking” of the clock to properties of the DNA sequence. Researchers may eventually use the results to select which genes make the best clocks.

Although mutations in DNA are rare, they are crucial for evolution. Each mutation in a gene changes one small piece of a protein molecule’s structure–sometimes rendering it non-functional and occasionally improving it. The vast majority of mutations, however, neither hurt nor help, often because they affect an unimportant part of their protein. Such a “neutral” mutation usually dies out over the generations, but occasionally one proliferates until virtually every individual has it, permanently “fixing” the mutation in the evolving species.

Over thousands of generations, these fixed mutations accumulate. To gauge the time since two species diverged from a common ancestor, biologists count the number of differences between stretches of their DNA. But different DNA segments (genes) often give different answers, and those answers differ by much more than would be expected if the average rate of mutations remained constant over evolutionary time. Sometimes they also disagree with dates inferred from fossils. Now Alpan Raval, of the Keck Graduate Institute and Claremont Graduate University, both in Claremont, California, has put precise mathematical limits on this variation.

Raval’s work is based on representing possible DNA sequences for a gene as a network of interconnected points or “nodes.” Each point represents a version of the gene sequence that differs by exactly one neutral mutation–a single DNA “letter”–from its immediate neighbors. The network contains only neutral mutations; non-functional versions of the sequence aren’t part of the network.

Models and simulations had suggested that if the number of neighbors varies from point to point–that is, if some sequences allow more neutral mutations than others–mutations accumulate erratically over time, making the molecular clock unreliable. Raval calculates precise limits on how unsteady the clock could get, based on properties of the network, such as the average number of neighbors for each node or the number of “jumps” connecting any two randomly chosen nodes. “The great strength of this paper is that it’s now mathematically worked out in much more detail than before,” says Erik van Nimwegen of the University of Basel and the Swiss Institute of Bioinformatics in Switzerland, who developed the framework that Raval uses.

Still, the relevant network properties are “not very intuitive,” van Nimwegen observes. Raval agrees. “The real question from this point on would be to identify what kinds of proteins would be good molecular clocks.” He says that according to his results, for a protein to be a good clock, “virtually all single mutations [should] be neutral”–many neighbors per node–but “as you start accumulating double and triple mutants, it should quickly become dysfunctional.” Raval is working to relate these network features to protein properties that researchers could measure in the lab.

Researchers have suggested other explanations for the erratic behavior of molecular clocks, such as variations in the mutation rate because of changes in the environment. But such environmental changes are relatively fast, so their effect should average out over evolutionary time, says David Cutler of Emory University in Atlanta. He says that in network models, by contrast, changes in the mutation rate are naturally slow because the point representing the current sequence moves slowly around the network as mutations accumulate.

Explanation:

4 0
3 years ago
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What is the difference between Pulmonary and Cellular Respiration?
marshall27 [118]
One is pulmonary one is cellular
3 0
3 years ago
1.) How do hurricanes form?
dalvyx [7]

Answer:

1.  there needs to be warm ocean water and moist, humid air in the region. When humid air is flowing upward at a zone of low pressure over warm ocean water, the water is released from the air as creating the clouds of the storm. As it rises, the air in a hurricane rotates.

2. Hurricanes are classified using the Saffir-Simpson Hurricane Wind Scale — a 1 to 5 rating that's based on maximum sustained wind speed, according to the National Hurricane Center.

3. When a hurricane strikes a coastal area, it brings a number of serious hazards. These hazards include heavy rains, high winds, a storm surge, and even tornadoes. Storm surge pushes seawater on shore during a hurricane, flooding towns near the coast. Heavy rains cause flooding in inland places as well.

Explanation:

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7 0
3 years ago
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Answer:

Explanation:

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3 years ago
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