PTE考生目前最大的问题之一就是练习题缺乏。除了有限的基本官方书（PLUS，Testbuilder, OG）之外，就没有题了。很多英语基础不是很扎实的同学很难找到练习材料。墨尔本文波雅思PTE培训学校专门为墨尔本，悉尼PTE考生准备了适合PTE听力阅读练习的科学60秒。各位PTE同学可以练习PTE听力中的summarise spoken text和PTE口语中的retell lecture，练习记笔记技巧和复述。废话少说，下面开始：
Give Us This Day the Bread Wheat Genome
60秒科学节目（SSS）是科学美国人网站的一套广播栏目，英文名称：Scientific American – 60 Second Science,节目内容以科学报道为主，节目仅一分钟的时间，主要对当今的科学技术新发展作以简明、通俗的介绍，对于科学的发展如何影响人们的生活环境、健康状况及科学技术，提供了大量简明易懂的阐释。
Wheat helped create civilization in the Middle East. It’s a staple crop for 30 percent of the world’s population. And now, with the publication of four articles in the journal Science, we’re close to a detailed understanding of the bread wheat genome. [Kellye Eversole et al, Slicing the wheat genome]
Wheat is tough to sequence. It’s gone through multiple hybridizations, making its genome five times larger than a human one. Plus there are many redundancies: more than 80 percent of the genome is made of repeated DNA sequences. So the typical whole-genome shotgun approach°™breaking genomes into segments and then reassembling them doesn’t work for wheat.
Instead, an international consortium devised another strategy, involving physically mapping individual chromosomes and chromosome arms.
One paper details a draft of the entire genome of bread wheat. Another identifies all the genes on the largest of the plant’s 21 chromosomes. Some 75,000 genes have been mapped. The methods in the second paper will help scientists map the remaining chromosomes. They say it should take another three years.
Knowing exactly which genes are responsible for talents such as tolerating drought or improving yields should allow researchers to mine the genome and to quickly produce new and better wheat varieties to bring us our daily bread.