题目:
关于黄疸的叙述中,下列哪一项是不正确的()
A.早产儿黄疸可延迟至第3周末
B.足月儿约于生后7~10天黄疸消退
C.生理性黄疸在生后2~3天出现,于4~5天达高峰
D.当血清胆红素>5~7mg/dl时肉眼才见黄疸
E.早产儿宜予以提前光疗,预防胆红素脑病
答案:
参考答案:A
关于黄疸的叙述中,下列哪一项是不正确的()
A.早产儿黄疸可延迟至第3周末
B.足月儿约于生后7~10天黄疸消退
C.生理性黄疸在生后2~3天出现,于4~5天达高峰
D.当血清胆红素>5~7mg/dl时肉眼才见黄疸
E.早产儿宜予以提前光疗,预防胆红素脑病
参考答案:A
煤气的用途不同,其工艺流程差别很大。但基本上包括三个主要的部分即()、()、()。
氮平衡指的是()。
A.尿与粪中含氮量与摄入食物中总含氮量的对比关系
B.每日摄入蛋白质的量与排除蛋白质量的对比关系
C.每日体内分解蛋白质量与合成蛋白质量的对比关系
D.尿与粪中含氮化合物总量与摄入含氮化合物总量对比关系
E.必需氨基酸与非必需氨基酸含量的对比关系
妇女定期进行疾病普查是针对()
A、以性传播疾病为主
B、以防癌为主
C、以防职业病为主
D、以保健为主
E、以妇女常见病为主
治疗此病的首选方为:
A.苍耳子散
B.清燥救肺汤
C.通窍汤
D.黄芩汤
E.桑菊饮
The human Y chromosome—the DNA chunk that makes a man a man—has lost so many genes over evolutionary time that some scientists have suspected it might disappear in 10 million years. But a new study says it’ll stick around.
Researchers found no sign of gene loss over the past 6 million years, suggesting the chromosome is "doing a pretty good job of maintaining itself," said researcher David Page of the Whitehead Institute for Biomedical Research in Cambridge, Mass.
That agrees with prior mathematical calculations that suggested the rate of gene loss would slow as the chromosome evolved, Page and study co-authors note in Thursday’s issue of the journal Nature. And, they say, it clashes with what Page called the "imminent demise" idea that says the Y chromosome is doomed to extinction.
The Y appeared 300 million years ago and has since eroded into a dinky chromosome, because it lacks the mechanism other chromosomes have to get rid of damaged DNA. So mutations have disabled hundreds of its original genes, causing them to be shed as useless. The Y now contains only 27 genes or families of virtually identical genes.
In 2003, Page reported that the modern-day Y has an unusual mechanism to fix about half of its genes and protect them from disappearing. But he said some scientists disagreed with his conclusion. The new paper focuses on a region of the Y chromosome where genes can’t be fixed that way.
Researchers compared the human and chimpanzee versions of this region. Humans and chimps have been evolving separately for about 6 million years, so scientists reasoned that the comparisons would reveal genes that have become disabled in one species or the other during that time.
They found five such genes on the chimp chromosome, but none on the human chromosome, an imbalance Page called surprising. "It looks like there has been little if any gene loss in our own species lineage in the last 6 million years," Page said. That contradicts the idea that the human Y chromosome has continued to lose genes so fast it’ll disappear in 10 million years, he said. "I think we can with confidence dismiss … the ’imminent demise’ theory," Page said.
Jennifer A. Marshall Graves of the Australian National University in Canberra, a gene researcher who argues for eventual extinction of the Y chromosome, called Page’s work "beautiful" but said it didn’t shake her conviction that the Y is doomed.
The only real question is when, not if, the Y chromosome disappears, she said. "It could be a lot shorter than 10 million years, but it could be a lot longer," she said.
The Y chromosome has already disappeared in some other animals, and "there’s no reason to expect it can’t happen to humans," she said. If it happened in people, some other chromosome would probably take over the sex-determining role of the Y, she said.
It can be inferred from the first 3 paragraphs that
[A] the human Y chromosome has stopped evolution.
[B] a man will no longer be a man in 10 million years.
[C] scientists are divided on the latest issue of Y chromosome.
[D] mathematical calculations are important in genetic studies.