Concept explainers
To review:
By using the phylogenetic tree given, it is required to construct hypothesis about the origin of the virus lineages by using virus isolates that are given on the right of the tree.
Given:
It is given that a virus which spread in West Nile killed many bird species and caused inflammation of the human brain and in horses. In 1930, it was first found in Africa. Then in 1990, it was found throughout Eurasia. In 1999, it was first detected in New York and spread across the United States. The phylogenetic tree of West Nile is shown below:
Introduction:
A phylogenetic tree shows evolutionary relationship among various biological species. It is important to reconstruct with the help of phylogenic tree to know the past of the biological processes. In case of infectious diseases, it is important to know that how, when and where disease initially entered the human body and population. This can be done by making a phylogenic tree and tracing traits of the diseases.
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Life: The Science of Biology
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- There have been recurring cases of mad-cow disease in the United Kingdom since the mid-1990s. Mad-cow disease is caused by a prion, an infectious particle that consists only of protein. In 1986, the media began reporting that cows all over England were dying from a mysterious disease. Initially, there was little interest in determining whether humans could be affected. For 10 years, the British government maintained that this unusual disease could not be transmitted to humans. However, in March 1996, the government did an about-face and announced that bovine spongiform encephalopathy (BSE), commonly known as mad-cow disease, can be transmitted to humans, where it is known as variant Creutzfeldt-Jakob disease (vCJD). As in cows, this disease eats away at the nervous system, destroying the brain and essentially turning it into a spongelike structure filled with holes. Victims experience dementia; confusion; loss of speech, sight, and hearing; convulsions; coma; and finally death. Prion diseases are always fatal, and there is no treatment. Precautionary measures taken in Britain to prevent this disease in humans may have begun too late. Many of the victims contracted it over a decade earlier, when the BSE epidemic began, and the incubation period is long (vCJD has an incubation period of 10 to 40 years). A recent study concluded that 1 in 2,000 people in Great Britain carry the abnormally folded protein that causes vCJD. In spite of these numbers, the death rate from vCJD remains low. It is not clear whether this means that the incubation period for the disease is much longer than previously thought, or whether they may never develop the disease. What measures have been taken to stop BSE?arrow_forwardFigure 17.5 Which of the following statements about virus structure is true? a. All viruses are encased in a viral membrane. b. The capsomere is made up of small protein subunits called capsids. c. DNA is the genetic material in all viruses. d. Glycoproteins help the virus attach to the host cell.arrow_forwardThe genome of a virus consists of (a) DNA (b) RNA (c) prions (d) DNA and RNA (e) DNA or RNAarrow_forward
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