Sanil D, Shetty N J
Centre for Applied Genetics, Bangalore University, J.B. Campus, Bengaluru & Janardhana Foundation, Nagadevanahalli,Jnanabharathi Post, Bengaluru, India.
J Vector Borne Dis. 2009 Jun;46(2):117-24.
BACKGROUND & OBJECTIVES: Anopheles stephensi, an important vector of malaria continues to be distributed widely in the Indian subcontinent. The natural vigour of the species combined with its new tolerance, indeed resistance to insecticides has made it obligatory that we look for control methods involving genetic manipulation. Hence, there is an immediate need for greater understanding of the genetics of this vector species. One of the requirements for such genetic studies is the establishment of naturally occurring mutants, establishment of the genetic basis for the same and use of such mutants in the genetic transformation studies and other genetic control programme(s). This paper describes the isolation and genetic studies of a larval colour mutant, green thorax (gt), and linkage studies involving another autosomal recessive mutant ruby- eye (ru) in An. stephensi.
After the initial discovery, the mutant green thorax was crossed inter se and pure homozygous stock of the mutant was established. The stock of the mutant ruby- eye, which has been maintained as a pure stock in the laboratory. Crosses were made between the wild type and mutant, green thorax to determine the mode of inheritance of green thorax. For linkage studies, crosses were made between the mutant green thorax and another autosomal recessive mutant ruby-eye. The percentage cross-over was calculated for the genes linkage relationship for gt and gt ru.
Results of crosses between mutant and wild type showed that the inheritance of green thorax (gt) in An. stephensi is monofactorial in nature. The gt allele is recessive to wild type and is autosomal. The linkage studies showed no linkage between ru and gt.
INTERPRETATION & CONCLUSION: The mutant gt represents an excellent marker for An. stephensi as it is expressed in late III instar stage of larvae and is prominent in IV instar and pupal stages with complete penetrance and high viability. The said mutant could be easily identified without the aid of a microscope. This mutant can be used extensively to conduct basic and applied research. The mutant has been maintained in two large cages in our laboratory.
斯氏按蚊是疟疾的重要传播媒介，在印度次大陆仍广泛分布。该物种的自然活力及其新获得的耐受性，实际上是对杀虫剂的抗性，使得我们必须寻找涉及基因操作的控制方法。因此，迫切需要更深入了解这种媒介物种的遗传学。此类遗传研究的要求之一是建立自然发生的突变体，确定其遗传基础，并在遗传转化研究和其他遗传控制计划中使用此类突变体。本文描述了斯氏按蚊幼虫颜色突变体绿胸（gt）的分离与遗传研究，以及涉及另一个常染色体隐性突变体红眼（ru）的连锁研究。
在最初发现后，将绿胸突变体进行互交，建立了该突变体的纯合品系。红眼突变体品系在实验室中一直作为纯系保存。将野生型与绿胸突变体进行杂交，以确定绿胸的遗传方式。为了进行连锁研究，将绿胸突变体与另一个常染色体隐性突变体红眼进行杂交。计算了gt和gt ru基因连锁关系的交换百分比。
突变体与野生型杂交的结果表明，斯氏按蚊中绿胸（gt）的遗传本质上是单因子的。gt等位基因对野生型是隐性的，且位于常染色体上。连锁研究表明ru和gt之间没有连锁关系。
突变体gt是斯氏按蚊的一个优良标记，因为它在幼虫晚期三龄期表达，在四龄期和蛹期很明显，具有完全的外显率和高活力。该突变体无需借助显微镜即可轻松识别。这个突变体可广泛用于基础研究和应用研究。该突变体已在我们实验室的两个大笼子中保存。
