专四专八考试

【单选题】
A、team of international researchers has found new evidence that an endangered subspecies of chimpanzee is the source of the virus that causes acquired immune deficiency syndromeAIDS) in humans.Experts said the finding could lead to new treatments forAIDS and contribute to the development of a vaccine against the disease.
The research team said the chimp -- a subspecies known as Pan troglodytes troglodytes native to west centralAfrica -- carries a simian immunodeficiency virus (SIV) that is closely related to three strains of human immunodeficiency virus ( HIV), the virus that causesAIDS. One of these strains, HIV - 1, has caused the vast majority of the estimated 30 million HIV infections around the worlD、
The researchers are uncertain when the chimp virus, called SIVcpz (for simian immunodeficiency virus chimpanzee), first infected humans, although the oldest documented case of HIV has been linked to aBantu man who died inCentralAfrica in 1959.But they said the virus, which does not appear to harm the chimps, was most likely transmitted to humans when hunters were exposed to chimp blood while killing and butchering the animals for fooD、Once transmitted to humans, the researchers believe the virus mutated into HIV -1.
Team leaderBeatrice Hahn, anAIDS researcher at the University ofAlabama inBirmingham, said the chimps have probably carried the virus for hundreds of thousands of years. Since humans have likely hunted the animals since prehistoric times, Hahn said the virus may have jumped to humans on many occasions, but was not trans, nined widely among humans until the 20th century.. Increased hunting of the chimpanzees, along with human migration toAfrican cities and changing sexual mores, could help explain the recent epidemixc, Hahn saiD、
Scientists had long suspected that a nonhuman primate was the source of HIV - 1.Earlier studies suggested that the sooty mangabey monkey, a native of WestAfrica, was the likely source of HIV - 2 -- a rarer torm of theAIDS virus that is transmitted less easily than HIV - 1. However, only a few samples of SIV strains exist, making it difficult for researehers to confidently connect the strains to HIV - 1.
As part of their effort to discover the source of HIV - 1, the research team studied the four known samples of SIVcpz. They learned that three of the four samples came from chimps belonging to the subspecies P.t. troglodytes. The remaining sample came from another subspecies, Pan troglodytes schweinfurthii, which inhabitsEastAfric
A、
The team then compared the SIVcpz strains to each other and found that all three of the viruses from P. t. troglodytes were closely related, while the virus from P.t. schweinfurthii was genetically different. Next they compared the SIVepz strains to the main subgroups of HIV - 1, known as M, N, and O. Their comparisons showed that the P.t. troglodytes viruses strongly resembled "all three HIV -1 subgroups.
Additional evidence that HIV - 1 could be linked to P. t. troglodytes came when the researchers examined the chimps’ natural habitat. The researchers quickly discovered that the chimps live primarily in the WestAfrican nations ofCameroon,CentralAfrican Republic, Gabon,Equatorial Guinea, and Republic of theCongo the geographic region where HIV - 1 was first identifieD、
Upon closer study, the researchers learned that the chimps were being killed in growing numbers for the so - called bush meat trade, a trend assisted by the construction of new logging roads in once remote forests. The researchers said that continued hunting of the animals meant that many people are still likely to be exposed to SIVepz, increasing the risk of additional cross - species transmissions.
ManyAIDS researchers welcomed the team’s finding, but said the new work had not proved the connection definitively. Most of the doubts centered on the difficulty of drawing conclusions from such a small numbe
网考网参考答案：B
网考网解析：
[详细解答] A是个事实，但非研究的意义所在。C意思不对。至于D，人类的研究将是漫长的，没那么乐观。只有B比较现实。 document.getElementById("warp").style.display="none"; document.getElementById("content").style.display="block"; 查看试题解析出处>>