11.25 病毒原源 -- -- 先进
Section outline
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Where did come from?
::哪里来的?Good question. This represents the AIDS virus, , one of the most researched viruses of all time. Why was such a deadly virus so recently discovered, appearing only in the early 1980s? Does this suggest that viruses are continuously evolving or that new viruses will continuously appear in our future? Maybe.
::问得好。 这代表了艾滋病病毒,这是有史以来研究最多的病毒之一。 为什么最近才发现如此致命的病毒,直到1980年代初才出现? 这是否意味着病毒在不断演变,或者新的病毒会持续出现在我们的未来?也许。Origins of Viruses
::病毒的起源The origins of modern viruses are not entirely clear. It may be that no single mechanism can account for the origin of all viruses. They do not fossilize well, so molecular techniques have been the most useful means of hypothesizing how they originated. Two main hypotheses currently exist:
::现代病毒的起源并不完全清楚。 可能是没有任何单一机制能够说明所有病毒的起源。 它们没有很好地化石化,因此分子技术是假设其起源的最有用手段。 目前存在两个主要假设:-
Small viruses with only a few
genes
may be runaway stretches of
that originally came from the
genome
of a living
organism
. Their
genetic material
could have come from transferable genetic
elements
such as
plasmids
or
transposons,
which can leave and enter genomes.
::仅有少数基因的小型病毒可能是最初来自活生物体基因组的外延,其遗传物质可能来自可转移的遗传要素,如可留下和进入基因组的粒子或转子。 -
Viruses with larger genomes, such as poxviruses, may have once been small
which parasitized larger
host
cells. Over time, genes not required by their parasitic lifestyle would have been lost because they were no longer needed; they provided no selective advantage during evolution. The
Rickettsia
and
Chlamydia
are bacterial cells that, like viruses, can only reproduce inside host cells. Their existence gives weight to this hypothesis, as their parasitic lifestyles are likely to have caused the loss of genes that allow them to survive outside a host cell.
::具有较大基因组的病毒,如天花病毒,曾经可能是很小的病毒,它们使较大的宿主细胞寄生。 随着时间的推移,它们寄生虫生活方式所不需要的基因会因为不再需要而丧失;它们在进化过程中没有提供选择性的优势。 Rickettsia和Chlamydia是细菌细胞,与病毒一样,只能在宿主细胞中繁殖。 它们的存在使这种假设变得重要,因为它们的寄生虫生活方式可能会导致基因的丧失,使他们得以在宿主细胞之外生存。
Summary
::摘要-
Viruses may have originated as breakaway pieces of genetic material from host organisms. Also, they could have originated as intracellular parasites that eventually lost most of their genome.
::病毒可能起源于宿主生物的分离基因材料,也可能起源于细胞内寄生虫,最终失去了大部分基因组。
-
Small viruses with only a few
genes
may be runaway stretches of
that originally came from the
genome
of a living
organism
. Their
genetic material
could have come from transferable genetic
elements
such as
plasmids
or
transposons,
which can leave and enter genomes.
