Researcher ORCID Identifier

https://orcid.org/0009-0007-0978-6475

Graduation Year

2025

Document Type

Campus Only Senior Thesis

Degree Name

Bachelor of Science

Department

Biology

Reader 1

Patrick Ferree

Reader 2

Emily Wiley

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Terms of Use for work posted in Scholarship@Claremont.

Rights Information

@ 2025 Anabhra Singh

Abstract

Various eukaryotes carry non-essential, selfish B chromosomes that transmit themselves at super-Mendelian frequencies, causing long-term fitness costs to the organism. A compelling question is what molecular characteristics allow B chromosomes to achieve high transmission. A key to answering this question is ascertaining the repertoire of genes expressed by B chromosomes and identifying which of them are important for transmission. Our group is addressing these goals by examining a B chromosome known as PSR (Paternal Sex Ratio) in the jewel wasp, Nasonia vitripennis. PSR, transmitted to progeny paternally, causes complete elimination of the sperm’s essential chromosomes, but not itself, during the first embryonic mitotic division following fertilization. Due to the haplo-diploid reproduction of N. vitripennis, this genome elimination event leads to the conversion of diploid, female-destined embryos into haploid males that can transmit PSR. This action facilitates PSR drive. Previously we used different genomic platforms to identify 75 PSR genes that are expressed in the testis. One PSR-expressed gene, haploidizer, is necessary for PSR’s genome elimination activity. It is unknown if this or other PSR-expressed genes encode functional proteins. We recently performed proteomics on three different tissue types – the young pupal reproductive tract, the adult reproductive tract, and the adult seminal vesicle – from the wild type and PSR+ males. From this work, we found that haploidizer does not produce any detectable peptides, arguing that this gene functions via non-coding RNA. Only a single gene (NV18026) produces a protein of 242 amino acids that was detectable in the adult male reproductive tract and the seminal vesicle, the site of sperm storage. Using systemic RNA interference, we targeted the NV18026 transcript in PSR males and observed no effect on PSR’s genome elimination activity. However, our preliminary findings suggest that the NV18026 protein may play a role in PSR transmission and segregation in mitotic divisions following paternal genome elimination. We also raised rabbit antibodies against the NV18026 protein. Immunofluorescence microscopy results indicate that this protein associates with elongating sperm chromatin. Ultimately, studying NV18026 is critical for investigating the functional, protein-coding potential of B chromosomes—both in driving B chromosome inheritance and in influencing the reproductive fitness of organisms.

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