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Research report: Analysis of the transformer gene in gynandromorph producing and normal strains of Nasonia vitripennis

Pan, Q. (2014) Research report: Analysis of the transformer gene in gynandromorph producing and normal strains of Nasonia vitripennis. Master's Thesis / Essay, Biology.

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Sex determination is an important and widespread developmental programme that involves a cascade of genes. Insect exhibits a high diversity of sex determination mechanism and diversification is found on the top of the cascade with various cues, including genetic, environmental or maternal signals. However, the bottom of the sex determination cascade is conserved with doublesex (dsx) and its splicing regulator transformer (tra). The regulator of tra has been proposed as the key aspect of diversification in insect sex determination as different species adopt various ways to turn on or off the production of TRA protein. Nasonia vitripennis, a parasitoid wasp, is an emerging model species in developmental and evolutionary biology. Nasonia, like all hymenoptera, has haplodiploid sex determination: females are diploid and develop from fertilized eggs, whereas males are haploid and develop from unfertilized eggs. Recently, the maternal effect genomic imprinting model (MEGISD) was proposed as the sex determination mechanism of N.vitripennis, although many mysteries still remain. A naturally occurring strain of N.vitripennis produces gynandromorph offspring, which are individuals with both female and male phenotypes. Previous study has revealed that a temperature sensitive maternal effect gene gyn1 is responsible for the production of gynandromorph offspring but cytoplasmic component are also essential. The proposed gene gyn1 is upstream of tra and is proposed to cause defects in silencing zygotic tra. However, the involvement of tra in producing gynandromorphs has not been elucidated. In this project, we first identified polymorphism on the sequence of tra between the gynandromorph producing strain (HiCD12) and a normal lab strain. Then association between tra polymorphism and the trait of producing gynandromorph progeny was tested with an introgression line created by crossing HiCD12 females to males from N.giraulti because that N.giraulti shows no gynandromorph production and there are species specific SNPs between these two sister species. Following that, with the same introgression line, we investigated whether gyn1 has an effect on the expression of tra in adult females by comparing the tra expression among gynandromorph-producing females and those who did not produce gynandromorph progeny. Lastly, species-specific SNPs analysis at the candidate region identified in previous study around dsx was carried out on the introgression line to search for location of gyn1. Our results suggest that suggest that mutations on the sequence of tra is not likely to be contributing to the production of gynandromorph progeny and gyn1 does not have a strong effect on the tra expression level in adult females.

Item Type: Thesis (Master's Thesis / Essay)
Degree programme: Biology
Thesis type: Master's Thesis / Essay
Language: English
Date Deposited: 15 Feb 2018 08:01
Last Modified: 15 Feb 2018 08:01

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