Use of Nasonia vitripennis to Evaluate Genomic Imprinting and Haplodiploid Inheritance

During fertilization, male and female gametes fuse and a diploid organism is generated. However, in some cases, not all of the genes from a parental genome are expressed. Such instances are known as genomic imprinting—when a gene from the genome of one parent is expressed and the respective gene from the other parental genome is silenced. When the gene that is meant to be expressed is absent or not functioning correctly, a genetic disorder can occur. In humans, such genetic disorders include Prader-Willi, Angelman, Beckwith-Wiedemann, and Silver-Russell syndromes. This experiment studies the effects of genomic imprinting in the parasitic wasp Nasonia vitripennis. This organism undergoes macro scale genomic imprinting during its sexual reproduction. When male genes are present in fertilized eggs, female offspring are produced. Conversely, when male genes are absent in unfertilized eggs, male offspring are produced. The results of the experimentation with Nasonia vitripennis strongly support the use of haplodiploid inheritance in the sexual reproduction of this species. Specifically, cross results for eyecolor exclude inheritance via standard dominant/ recessive genetics. In summary, this study focuses on the sexual reproduction of Nasonia vitripennis through haplodiploid inheritance, the relevance to genomic imprinting, and how studying genomic imprinting in Nasonia vitripennis allows for understanding of the genomic imprinting in humans. This article is available in The Review: A Journal of Undergraduate Student Research: http://fisherpub.sjfc.edu/ur/vol8/iss1/6 Use oiNasonia vitripennis to Evaluate Genomic Imprinting and Haplodiploid Inheritance Carolyn L. Fisher February 27, 2006 Abstract: During fertilization, male and female gametes fuse and a diploid organism is generated. However, in some cases, not all of the genes from a parental genome are expressed. Such instances are known as genomic imprinting—when a gene from the genome of one parent is expressed and the respective gene from the other parental genome is silenced. When the gene that is meant to be expressed is absent or not functioning correctly, a genetic disorder can occur. In humans, such genetic disorders include PraderWilli, Angelman, Beckwith-Wiedemann, and Silver-Russell syndromes. This experiment studies the effects of genomic imprinting in the parasitic wasp Nasonia vitripennis. This organism undergoes macro scale genomic imprinting during its sexual reproduction. When male genes are present in fertilized eggs, female offspring are produced. Conversely, when male genes are absent in unfertilized eggs, male offspring are produced. The results of the experimentation with Nasonia vitripennis strongly support the use of haplodiploid inheritance in the sexual reproduction of this species. Specifically, cross results for eyecolor exclude inheritance via standard dominant/recessive genetics. In summary, this study focuses on the sexual reproduction of Nasonia vitripennis through haplodiploid inheritance, the relevance to genomic imprinting, and how studying genomic imprinting in Nasonia vitripennis allows for understanding of the genomic imprinting in humans. During fertilization, male and female gametes fuse and a diploid organism is generated. However, in some cases, not all of the genes from a parental genome are expressed. Such instances are known as genomic imprinting—when a gene from the genome of one parent is expressed and the respective gene from the other parental genome is silenced. When the gene that is meant to be expressed is absent or not functioning correctly, a genetic disorder can occur. In humans, such genetic disorders include PraderWilli, Angelman, Beckwith-Wiedemann, and Silver-Russell syndromes. This experiment studies the effects of genomic imprinting in the parasitic wasp Nasonia vitripennis. This organism undergoes macro scale genomic imprinting during its sexual reproduction. When male genes are present in fertilized eggs, female offspring are produced. Conversely, when male genes are absent in unfertilized eggs, male offspring are produced. The results of the experimentation with Nasonia vitripennis strongly support the use of haplodiploid inheritance in the sexual reproduction of this species. Specifically, cross results for eyecolor exclude inheritance via standard dominant/recessive genetics. In summary, this study focuses on the sexual reproduction of Nasonia vitripennis through haplodiploid inheritance, the relevance to genomic imprinting, and how studying genomic imprinting in Nasonia vitripennis allows for understanding of the genomic imprinting in humans. Introduction: At fertilization, maternal and paternal genomes come together to establish a new and unique organism through the fusion of genetic material from both male and female gametes. Therefore, this new organism inherits genetic material from both the male and female gametes. However, not all genes from both gametes will be developmentally expressed. Specific genes from both the maternal and paternal genomes will be silenced, or imprinted, to allow for the correct developmental pattern to proceed'. A genetic disorder occurs when such genes are inappropriately inherited or expressed in the genetic makeup of an individual. Such genetic disorders include Prader-Willi, Angelman, Beckwith-Wiedemann, and Silver-Russell syndromes. Research on genomic imprinting with the parasitic wasp Nasonia vitripennis has helped scientists to better understand how imprinting affects an individual. The PSR chromosome in some Nasonia vitripennis males has also been linked to genomic imprinting and, thus, is of major interest to scientists in this field. Through continued research of imprinting in Nasonia vitripennis, a greater understanding of the mechanisms of imprinting will be acquired. This may in turn lead to a greater understanding of similar genetic disorders in humans. The human genome usually includes 46 chromosomes, or 23 pairs of chromosomes. Half of these chromosomes are paternal and half are maternal. Different genes are located on different chromosomes and most genes contribute to more than one trait for an individual. Some traits, such as eye color, result from multiple genes, inherited from both parents, interacting in a complex network of genes. However, with imprinting, a gene is only "inherited" from the maternal or paternal chromosome because the gene from the other chromosome has been silenced (imprinted). With imprinting, there is an absolute requirement for gene expression from the appropriate chromosome (maternal or paternal) for correct development to occur. Therefore, if a gene that must be expressed is missing, the resultant individual will suffer from a range of genetic disorders. The gene could be "missing" for one of three reasons: (1) it was deleted from the particular chromosome, (2) two copies of the chromosome were inherited from one parent and the gene is only expressed on the chromosome of the other parent, or (3) the gene on the chromosome becomes inactive and fails to contribute to the genetic makeup of the individual . Regardless of the mechanism, an individual will be born with a genetic disorder specific to the chromosome and the gene that is absent.