英语翻译我这里还有一部分内容不是很明了,能否请你帮忙翻译一下,A project to sequence the bov

英语翻译
我这里还有一部分内容不是很明了,能否请你帮忙翻译一下,
A project to sequence the bovine genome started in 2003 and the first draft
sequence with three-fold coverage of the genome was made publicly available in
November 2004.首先是这一句,其中“ three-fold coverage of the genome”想了很久都没有明白到底是什么意思,
2.4.4 MAPPING POPULATIONS
The second requirement to map QTLs,in addition to the genetic markers,is families
segregating and recorded for the traits of interest.Unfortunately,the range of traits
routinely recorded in commercial populations is very limited,and through necessity
has focused on simple traits,such as growth rates and milk yields.An additional
consideration is that traits are often sex specific,and although selection is applied
most strongly in the males,because of artificial insemination(AI),the trait is often
expressed in the females.In the case of meat quality accurate measurements of the
traits can only be done postslaughter,and thus cannot be made in the animals
intended for breeding.
The structure of the commercial dairy population includes a large number of
half-sib cows produced by AI from a limited number of elite bulls.This population
structure is particularly appropriate for mapping QTL.The genetic contribution of
bulls to milk production traits can be determined with high accuracy by measuring
the phenotypes of their daughters.Bulls with high breeding value are then used
extensively through AI to improve the dairy cow population.The sons of bulls with
high breeding values are in turn used as AI sires to produce a large number of
daughters.Georges et al.(1995)used the U.S.Holstein population to map QTL
involved in milk yield.Five QTL for dairy-associated traits were identified,many
of which have been confirmed independently in subsequent studies in other popu-
lations(e.g.,Kuhn,Freyer,Weikard,Goldammer,and Schwerin 1999;Wiener,
Maclean,Williams,and Woolliams 2000).还有这一章节,完全不明白在讲什么,如果你方便的话,能否帮我也翻译一下,实在是很急,没有头绪,麻烦你了!

测序要在后期数据处理是根据断裂处的重叠序列信息进行拼接的.如果工作量只是基因组的一倍就无法获得断裂处的重叠序列信息,最后只有一堆短片段的序列信息.为了准确有效的拼接,测序工作量就需要数倍于基因组,three-fold coverage of the genome就是三倍于基因组,这并不能算是高,测序的结果也就是draft的.
2.4.4 作图群体
其次,进行QTLs作图在遗传标记之外,还需要家系分离和目标性状的数据记载.但是,商业生产所用群体的性状记录常常很有限,且一般仅仅是着重于一些简单的性状,如生长率和产奶量.此外,我们还有考虑到不同性别的性状差异.由于人工受精的存在,选择作用被强有力的应用于父本,一些性状就常常在母本中得到表达.例如肉质的精确测定只能在动物被屠宰后才好进行,因此该性状就不适宜用于育种的动物性状调查.
商业化生产牛奶的群体结构包含大量的半同胞奶牛.它们是由有限的高品种公牛通过人工受精的方式产生的.这样的群体结构适用于QTLs作图.公牛对奶产量性状的遗传贡献率可通过其后代母牛的表型进行测定.具高育种值的公牛通过人工受精的方式广泛地应用于改良日常奶牛群体.具高育种值公牛的雄性子代被用作人工受精的公畜,进而繁殖大量的奶牛.Georges等人1995年利用U.S.Holstein群体进行了奶产量相关的QTL作图,检测到5个奶相关性状的QTLs.这些QTLs大多也被利用其他群体的后续研究分别证实（如,Kuhn,Freyer,Weikard,Goldammer,and Schwerin 1999;Wiener,
Maclean,Williams,and Woolliams 2000）.
你做的是动物遗传?先多看点国语的关于你做的方面的综述之类的再看外文就好多了.仅作参考,我们不做动物,呵呵