A shortage of genes could be to blame for the lack of height in short people, researchers have found.


　　Two studies involving 12,000 people has been carried out in America and found a link between the amount of missing genetic material and a decrease in height.


　　Height is mostly passed down through families but scientists say this does not explain everything when comparing the variations between people.


　　Dr Joel Hirschhorn, who led a study published in the American Journal of Human Genetics, said: "Despite tremendous recent progress in finding common genetic variants associated with height, thus far these variants only explain about 10 percent of the variation in adult height."


　　Researchers now believe that missing copies of genes or other sections of DNA could be the reason behind up to half of the genetic impact on people's height.


　　Known as copy number variants (CNV)， the genetic abnormalities are alterations within the chromosome which means a cell has an excess or an absence of a slice of DNA.


　　Some CNVs are common, but others are rare or occur with low frequency among humans.


　　And the researchers found an excess of low frequency CNV deletions - where part of the genome is missing - in shorter people.


　　There is a wide variation in the amount of these CNV deletions which people have in their genome, with some people having several million.


　　The researchers from the Children's Hospital Boston found that for every million individual deletions, one eighth of an inch in height was lost in people.


　　据英国《每日邮报》11月24日报道，研究人员发现，基因数量不足可能是人身高较低的原因。


　　在美国进行的两项涉及1.2万人的调查研究发现了缺失基因的数量与身高降低之间的关系。


　　身高主要通过家族遗传，但是科学家说，在比较人与人之间的不同之处时，这个原因并不能解释所有问题。


　　乔尔·何塞豪恩主持了这项研究，研究成果发表在美国的《人类遗传学》杂志上，他说：“尽管一般的遗传变异与身高方面关联的研究近期取得了重大的进展，但迄今为止，这种遗传变异仅仅能解释10%的成年人身高变化的原因。”


　　研究人员现在认为，成人在身高方面受基因影响的背后原因，有一半可能是因为缺失基因副本或是DNA组成部分。


　　被称为拷贝数变异(CNV)的基因异常是染色体内部的改变。这意味着，一个细胞可能会多出或缺少一片DNA。


　　有些拷贝数变异是很常见的，但还有一些则在人类中极少发生或是发生的频率较低。


　　研究人员发现，在个子比较矮的人身上，会出现低发生率拷贝数变异过剩——部分基因组缺失。


　　人类基因组拷贝数变异缺失在数量上也有很大的不同，有些人的缺失数甚至能达到几百万。


　　波士顿儿童医院的研究人员发现，每一百万个基因缺失就会使身高下降八分之一英寸。