Genetics and Genomics Commons^™

Factors Associated With Blood Mercury Concentrations And Their Interactions With Three Glutathione S-Transferase Genes (Gstt1, Gstm1, And Gstp1): An Exposure Assessment Study Of Typically Developing Jamaican Children, Sheikh Farzana Zaman, Maureen Samms-Vaughan, Sepideh Saroukhani, Jan Bressler, Manouchehr Hessabi, Megan L Grove, Sydonnie Shakespeare Pellington, Katherine A Loveland, Mohammad H Rahbar

Faculty and Staff Publications

BACKGROUND: Jamaican soil is abundant in heavy metals including mercury (Hg). Due to availability and ease of access, fish is a traditional dietary component in Jamaica and a significant source of Hg exposure. Mercury is a xenobiotic and known neuro-toxicant that affects children's neurodevelopment. Human glutathione S-transferase (GST) genes, including GSTT1, GSTM1, and GSTP1, affect Hg conjugation and elimination mechanisms.

METHODS: In this exposure assessment study we used data from 375 typically developing (TD) 2-8-year-old Jamaican children to explore the association between environmental Hg exposure, GST genes, and their interaction effects on blood Hg concentrations (BHgCs). We used multivariable general …

Genome-Wide Bidirectional Crispr Screens Identify Mucins As Host Factors Modulating Sars-Cov-2 Infection, Scott B Biering, Sylvia A Sarnik, Eleanor Wang, James R Zengel, Sarah R Leist, Alexandra Schäfer, Varun Sathyan, Padraig Hawkins, Kenichi Okuda, Cyrus Tau, Aditya R Jangid, Connor V Duffy, Jin Wei, Rodney C Gilmore, Mia Madel Alfajaro, Madison S Strine, Xammy Nguyenla, Erik Van Dis, Carmelle Catamura, Livia H Yamashiro, Julia A Belk, Adam Begeman, Jessica C Stark, D Judy Shon, Douglas M Fox, Shahrzad Ezzatpour, Emily Huang, Nico Olegario, Arjun Rustagi, Allison S Volmer, Alessandra Livraghi-Butrico, Eddie Wehri, Richard R Behringer, Dong-Joo Cheon, Julia Schaletzky, Hector C Aguilar, Andreas S Puschnik, Brian Button, Benjamin A Pinsky, Catherine A Blish, Ralph S Baric, Wanda K O'Neal, Carolyn R Bertozzi, Craig B Wilen, Richard C Boucher, Jan E Carette, Sarah A Stanley, Eva Harris, Silvana Konermann, Patrick D Hsu

Student and Faculty Publications

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes a range of symptoms in infected individuals, from mild respiratory illness to acute respiratory distress syndrome. A systematic understanding of host factors influencing viral infection is critical to elucidate SARS-CoV-2-host interactions and the progression of Coronavirus disease 2019 (COVID-19). Here, we conducted genome-wide CRISPR knockout and activation screens in human lung epithelial cells with endogenous expression of the SARS-CoV-2 entry factors ACE2 and TMPRSS2. We uncovered proviral and antiviral factors across highly interconnected host pathways, including clathrin transport, inflammatory signaling, cell-cycle regulation, and transcriptional and epigenetic regulation. We further identified mucins, a …

Biallelic Variants In Pcdhgc4 Cause A Novel Neurodevelopmental Syndrome With Progressive Microcephaly, Seizures, And Joint Anomalies, Maria Iqbal, Reza Maroofian, Büşranur Çavdarlı, Florence Riccardi, Michael Field, Siddharth Banka, Dalal K. Bubshait, Yun Li, Jozef Hertecant, Shahid Mahmood Baig

Department of Biological & Biomedical Sciences

Purpose: We aimed to define a novel autosomal recessive neurodevelopmental disorder, characterize its clinical features, and identify the underlying genetic cause for this condition.
Methods: We performed a detailed clinical characterization of 19 individuals from nine unrelated, consanguineous families with a neurodevelopmental disorder. We used genome/exome sequencing approaches, linkage and cosegregation analyses to identify disease-causing variants, and we performed three-dimensional molecular in silico analysis to predict causality of variants where applicable.
Results: In all affected individuals who presented with a neurodevelopmental syndrome with progressive microcephaly, seizures, and intellectual disability we identified biallelic disease-causing variants in Protocadherin-gamma-C4 (PCDHGC4). Five variants were …

N-Terminal Domain Of Human Uracil Dna Glycosylase (Hung2) Promotes Targeting To Uracil Sites Adjacent To Ssdna-Dsdna Junctions, Brian P Weiser, Gaddiel Rodriguez, Philip A Cole, James T Stivers

Rowan-Virtua School of Osteopathic Medicine Departmental Research

The N-terminal domain (NTD) of nuclear human uracil DNA glycosylase (hUNG2) assists in targeting hUNG2 to replication forks through specific interactions with replication protein A (RPA). Here, we explored hUNG2 activity in the presence and absence of RPA using substrates with ssDNA-dsDNA junctions that mimic structural features of the replication fork and transcriptional R-loops. We find that when RPA is tightly bound to the ssDNA overhang of junction DNA substrates, base excision by hUNG2 is strongly biased toward uracils located 21 bp or less from the ssDNA-dsDNA junction. In the absence of RPA, hUNG2 still showed an 8-fold excision bias …

The Zinc Transporter Zipt-7.1 Regulates Sperm Activation In Nematodes, Yanmei Zhao, Chieh-Hsiang Tan, Amber Krauchunas, Andrea Scharf, Nicholas Dietrich, Kurt Warnhoff, Zhiheng Yuan, Marina Druzhinina, Sam Guoping Gu, Long Miao, Andrew Singson, Ronald E Ellis, Kerry Kornfeld

Rowan-Virtua School of Osteopathic Medicine Departmental Research

Sperm activation is a fascinating example of cell differentiation, in which immotile spermatids undergo a rapid and dramatic transition to become mature, motile sperm. Because the sperm nucleus is transcriptionally silent, this transition does not involve transcriptional changes. Although Caenorhabditis elegans is a leading model for studies of sperm activation, the mechanisms by which signaling pathways induce this transformation remain poorly characterized. Here we show that a conserved transmembrane zinc transporter, ZIPT-7.1, regulates the induction of sperm activation in Caenorhabditis nematodes. The zipt-7.1 mutant hermaphrodites cannot self-fertilize, and males reproduce poorly, because mutant spermatids are defective in responding to activating …

A Behavioral Prerequisite For The Genetic Analysis Of Auditory Feature Detection Mechanisms In Female Crickets, Rebecca L. Blisko

Senior Honors Projects

Sexual dimorphism is exhibited across all cricket species and is a central aspect of the mating processes of these insects. Only male crickets possess wing structures and pattern generators in the central nervous system that allow them to produce a mating call that is unique to their species in order to attract conspecific females. Conspecific females possess an auditory feature detection circuit in the central nervous system that is capable of detecting the species-specific frequency and temporal pattern of sound pulses within a male call. In order for dimorphic differences in mating behavior to result in successful continuation of a …

Hereditary Sensory Autonomic Neuropathy Ii, A Rare Disease In A Large Pakistani Family, Fazal M. Arain, Prem Chand

Department of Paediatrics and Child Health

Hereditary Sensory Autonomic Neuropathy II (HSAN II) is a rare genetic disorder, characterized by severe loss of pain, temperature and touch sensation. Injuries in these patients can progress to necrosis and shedding of digits and limbs. Here we report two cases of HSAN II belonging to a Pakistani family. Individual 1, a forty five year old man, had complete loss of pain sensation since birth. Self-mutilation and complication of injuries resulted in the shedding of all the digits and right foot and surgical amputation of left leg. Individual 2, a five year old girl,had delay in healing of wounds and …

Employing Limited Next Generation Sequence Data For The Development Of Genetic Loci Of Phylogenetic And Population Genetic Utility, Lauren Evenstone

FIU Electronic Theses and Dissertations

Massively parallel high throughput sequencers are transforming the scientific research by reducing the cost and time necessary to sequence entire genomes. The goal of this project is to produce preliminary genome assemblies of calliphorid flies using Life Technologies’ Ion Torrent sequencing and Illumina’s MiSeq sequencing. I located, assembled, and annotated a novel mitochondrial genome for one such fly, the little studied Chrysomya pacifica that is central to one hypothesis about blow fly evolution. With sequencing data from Chrysomya megacephala, its forensically relevant sister species, much insight can be gained by alignments, sequence and protein analysis, and many more tools …

Childhood Obesity And Familial Hypercholesterolemia: Genetic Diseases That Contribute To Cardiovascular Disease, Alyssa Caudle

Senior Honors Theses

Childhood obesity occurs as the result of an imbalance between caloric intake and energy expenditure. Genetic risk factors for obesity have become an area of research due to its permanency. Mutated genes such as Fat Mass and Obesity Associated (FTO), Leptin (LEP), Leptin Receptor (LEPR), Melanocortin 4 Receptor (MC4R), Adiponectin C1Q and Collagen Domain Containing (ADIPOQ), Proprotein Convertase Subtilisin/Kexin Type 1 (PCSK1), and Peroxisome Proliferator-Activated Receptor Gamma (PPARG) all contribute to the development of childhood obesity. In the presence of high cholesterol caused by obesity, the genetic condition known as familial hypercholesterolemia is exacerbated. Familial hypercholesterolemia is caused by a …

Exploration Of The Genetic Epidemiology Of Asthma: A Review, With A Focus On Prevalence In Children And Adolescents In The Caribbean, A. Mohan, A. J. Roberto, B. C. Whitehill, A. Mohan, A. Kumar

Biological Sciences Faculty Publications

Asthma is a chronic disease caused by the inflammation of the main air passages of the lungs. This paper outlines a review of the published literature on asthma. While a few studies show a trend of rising asthma cases in the Caribbean region, even fewer have explored the genetic epidemiological factors of asthma. This is a literature review that seeks to sum the body of knowledge on the epidemiology of asthma. Specifically, the major objective of the literature review is to provide a unified information base on the current state of factors involved in the genetic epidemiology of asthma. The …

An Intergenic Region Shared By At4g35985 And At4g35987 In Arabidopsis Thaliana Is A Tissue Specific And Stress Inducible Bidirectional Promoter Analyzed In Transgenic Arabidopsis And Tobacco Plants, Joydeep Banerjee, Dipak K. Sahoo, Nrisingha Dey, Robert Houtz, Indu B. Maiti

Kentucky Tobacco Research and Development Center Faculty Publications

On chromosome 4 in the Arabidopsis genome, two neighboring genes (calmodulin methyl transferase At4g35987 and senescence associated gene At4g35985) are located in a head-to-head divergent orientation sharing a putative bidirectional promoter. This 1258 bp intergenic region contains a number of environmental stress responsive and tissue specific cis-regulatory elements. Transcript analysis of At4g35985 and At4g35987 genes by quantitative real time PCR showed tissue specific and stress inducible expression profiles. We tested the bidirectional promoter-function of the intergenic region shared by the divergent genes At4g35985 and At4g35987 using two reporter genes (GFP and GUS) in both orientations in transient tobacco protoplast and …

Differential Regulation Of White-Opaque Switching By Individual Subunits Of Candida Albicans Mediator, Anda Zhang, Zhongle Liu, Lawrence C. Myers

Dartmouth Scholarship

The multisubunit eukaryotic Mediator complex integrates diverse positive and negative gene regulatory signals and transmits them to the core transcription machinery. Mutations in individual subunits within the complex can lead to decreased or increased transcription of certain subsets of genes, which are highly specific to the mutated subunit. Recent studies suggest a role for Mediator in epigenetic silencing. Using white-opaque morphological switching in Candida albicans as a model, we have shown that Mediator is required for the stability of both the epigenetic silenced (white) and active (opaque) states of the bistable transcription circuit driven by the master regulator Wor1. Individual …

Farnesol And Cyclic Amp Signaling Effects On The Hypha-To-Yeast Transition In Candida Albicans, Allia K. Lindsay, Aurélie Deveau, Amy E. Piispanen, Deborah A. Hogan

Dartmouth Scholarship

Candida albicans, a fungal pathogen of humans, regulates its morphology in response to many environmental cues and this morphological plasticity contributes to virulence. Farnesol, an autoregulatory molecule produced by C. albicans, inhibits the induction of hyphal growth by inhibiting adenylate cyclase (Cyr1). The role of farnesol and Cyr1 in controlling the maintenance of hyphal growth has been less clear. Here, we demonstrate that preformed hyphae transition to growth as yeast in response to farnesol and that strains with increased cyclic AMP (cAMP) signaling exhibit more resistance to farnesol. Exogenous farnesol did not induce the hypha-to-yeast transition in mutants …

Dna Methylation Arrays As Surrogate Measures Of Cell Mixture Distribution, Eugene Houseman, William P. Accomando, Devin C. Koestler, Brock C. Christensen, Carmen J. Marsit

Dartmouth Scholarship

There has been a long-standing need in biomedical research for a method that quantifies the normally mixed composition of leukocytes beyond what is possible by simple histological or flow cytometric assessments. The latter is restricted by the labile nature of protein epitopes, requirements for cell processing, and timely cell analysis. In a diverse array of diseases and following numerous immune-toxic exposures, leukocyte composition will critically inform the underlying immuno-biology to most chronic medical conditions. Emerging research demonstrates that DNA methylation is responsible for cellular differentiation, and when measured in whole peripheral blood, serves to distinguish cancer cases from controls.

High Ethanol Titers From Cellulose By Using Metabolically Engineered Thermophilic, Anaerobic Microbes, D. Aaron Argyros, Shital A. Tripathi, Trisha F. Barrett, Stephen R. Rogers, Lawrence F. Feinberg, Daniel G. Olson, Justin M. Foden, Bethany B. Miller, Lee R. Lynd, David A. Hogsett, Nicky C. Caiazza

Dartmouth Scholarship

This work describes novel genetic tools for use in Clostridium thermocellum that allow creation of unmarked mutations while using a replicating plasmid. The strategy employed counter-selections developed from the native C. thermocellum hpt gene and the Thermoanaerobacterium saccharolyticum tdk gene and was used to delete the genes for both lactate dehydrogenase (Ldh) and phosphotransacetylase (Pta). The Δldh Δpta mutant was evolved for 2,000 h, resulting in a stable strain with 40:1 ethanol selectivity and a 4.2-fold increase in ethanol yield over the wild-type strain. Ethanol production from cellulose was investigated with an engineered coculture of organic acid-deficient engineered strains of …

Ecology And Genetic Structure Of A Northern Temperate Vibrio Cholerae Population Related To Toxigenic Isolates, Brian M. Schuster, Anna L. Tyzik, Rachel A. Donner, Megan J. Striplin, Salvador Almagro-Moreno

Dartmouth Scholarship

Although Vibrio cholerae is an important human pathogen, little is known about its populations in regions where the organism is endemic but where cholera disease is rare. A total of 31 independent isolates confirmed as V. cholerae were collected from water, sediment, and oysters in 2008 and 2009 from the Great Bay Estuary (GBE) in New Hampshire, a location where the organism has never been detected. Environmental analyses suggested that abundance correlates most strongly with rainfall events, as determined from data averaged over several days prior to collection. Phenotyping, genotyping, and multilocus sequence analysis (MLSA) revealed a highly diverse endemic …

Excision Dynamics Of Vibrio Pathogenicity Island-2 From Vibrio Cholerae: Role Of A Recombination Directionality Factor Vefa, Salvador Almagro-Moreno, Michael G. Napolitano, E. Fidelma Boyd

Dartmouth Scholarship

Vibrio Pathogenicity Island-2 (VPI-2) is a 57 kb region present in choleragenic V. cholerae isolates that is required for growth on sialic acid as a sole carbon source. V. cholerae non-O1/O139 pathogenic strains also contain VPI-2, which in addition to sialic acid catabolism genes also encodes a type 3 secretion system in these strains. VPI-2 integrates into chromosome 1 at a tRNA-serine site and encodes an integrase intV2 (VC1758) that belongs to the tyrosine recombinase family. ntV2 is required for VPI-2 excision from chromosome 1, which occurs at very low levels, and formation of a non-replicative circular intermediate.

Physical Interaction Between Vivid And White Collar Complex Regulates Photoadaptation In Neurospora, Chen-Hui H. Chen, Bradley S. Demay, Amy S. Gladfelter, Jay Dunlap, Jennifer J. Loros

Dartmouth Scholarship

Photoadaptation, the ability to attenuate a light response on prolonged light exposure while remaining sensitive to escalating changes in light intensity, is essential for organisms to decipher time information appropriately, yet the underlying molecular mechanisms are poorly understood. In Neurospora crassa, VIVID (VVD), a small LOV domain containing blue-light photoreceptor protein, affects photoadaptation for most if not all light-responsive genes. We report that there is a physical interaction between VVD and the white collar complex (WCC), the primary blue-light photoreceptor and the transcription factor complex that initiates light-regulated transcriptional responses in Neurospora. Using two previously characterized VVD mutants, we show …

Quantifying And Resolving Multiple Vector Transformants In S. Cerevisiae Plasmid Libraries, Thomas C. Scanlon, Elizabeth C. Gray, Karl E. Griswold

Dartmouth Scholarship

In addition to providing the molecular machinery for transcription and translation, recombinant microbial expression hosts maintain the critical genotype-phenotype link that is essential for high throughput screening and recovery of proteins encoded by plasmid libraries. It is known that Escherichia coli cells can be simultaneously transformed with multiple unique plasmids and thusly complicate recombinant library screening experiments. As a result of their potential to yield misleading results, bacterial multiple vector transformants have been thoroughly characterized in previous model studies. In contrast to bacterial systems, there is little quantitative information available regarding multiple vector transformants in yeast. Saccharomyces cerevisiae is the …

Constructing And Using Case Studies In Genetics To Engage Students In Active Learning, Sue Styer

Faculty Publications & Research

One of the national goals in science education is to teach science in a way that mirrors the process of science as inquiry, described by the National Science Education Standards (NSES) Science Teaching Standard B and Content Standard A (NRC, 1996). Inquiry-based learning, including the use of case studies, is one of several types of active learning that allows students to experience critical thinking skills inherent in the science process (Handelsman et al., 2007). Using case studies also develops skills in group learning and personalizes and humanizes science, making it more relevant to students (National Center for Case Study Teaching …

Efficient Gene Replacements In Toxoplasma Gondii Strains Deficient For Nonhomologous End Joining, Barbara A. Fox, Jessica G. Ristuccia, Jason P. Gigley, David J. Bzik

Dartmouth Scholarship

A high frequency of nonhomologous recombination has hampered gene targeting approaches in the model apicomplexan parasite Toxoplasma gondii. To address whether the nonhomologous end-joining (NHEJ) DNA repair pathway could be disrupted in this obligate intracellular parasite, putative KU proteins were identified and a predicted KU80 gene was deleted. The efficiency of gene targeting via double-crossover homologous recombination at several genetic loci was found to be greater than 97% of the total transformants in KU80 knockouts. Gene replacement efficiency was markedly increased (300- to 400-fold) in KU80 knockouts compared to wild-type strains. Target DNA flanks of only approximately 500 bp were …

Evolution Acts On Enhancer Organization To Fine-Tune Gradient Threshold Readouts, Justin Crocker, Yoichiro Tamori, Albert Erives

Dartmouth Scholarship

The elucidation of principles governing evolution of gene regulatory sequence is critical to the study of metazoan diversification. We are therefore exploring the structure and organizational constraints of regulatory sequences by studying functionally equivalent cis-regulatory modules (CRMs) that have been evolving in parallel across several loci. Such an independent dataset allows a multi-locus study that is not hampered by nonfunctional or constrained homology. The neurogenic ectoderm enhancers (NEEs) of Drosophila melanogaster are one such class of coordinately regulated CRMs. The NEEs share a common organization of binding sites and as a set would be useful to study the relationship …

Ovarian Development In Mice Requires The Gata4-Fog2 Transcription Complex, Nikolay L. Manuylov, Fatima O. Smagulova, Lyndsay Leach, Sergei G. Tevosian

Dartmouth Scholarship

We have demonstrated previously that mammalian sexual differentiation requires both the GATA4 and FOG2 transcriptional regulators to assemble the functioning testis. Here we have determined that the sexual development of female mice is profoundly affected by the loss of GATA4-FOG2 interaction. We have also identified the Dkk1 gene, which encodes a secreted inhibitor of canonical beta-catenin signaling, as a target of GATA4-FOG2 repression in the developing ovary. The tissue-specific ablation of the beta-catenin gene in the gonads disrupts female development. In Gata4(ki/ki); Dkk1(-/-) or Fog2(-/-); Dkk1(-/-) embryos, the normal ovarian gene expression pattern is partially restored. Control of ovarian development …

Systems Approach Identifies An Organic Nitrogen-Responsive Gene Network That Is Regulated By The Master Clock Control Gene Cca1, Rodrigo A. Gutierrez, Trevor L. Stokes, Karen Thum, Xiaodong Xu, Mariana Obertello, Manpreet S. Katari, Milos Tanurdzic, Alexis Dean, Damion C. Nero, C Robertson Mcclung, Gloria M. Coruzzi

Dartmouth Scholarship

Understanding how nutrients affect gene expression will help us to understand the mechanisms controlling plant growth and development as a function of nutrient availability. Nitrate has been shown to serve as a signal for the control of gene expression in Arabidopsis. There is also evidence, on a gene-by-gene basis, that downstream products of nitrogen (N) assimilation such as glutamate (Glu) or glutamine (Gln) might serve as signals of organic N status that in turn regulate gene expression. To identify genome-wide responses to such organic N signals, Arabidopsis seedlings were transiently treated with ammonium nitrate in the presence or absence of …

Variation In Molybdenum Content Across Broadly Distributed Populations Of Arabidopsis Thaliana Is Controlled By A Mitochondrial Molybdenum Transporter (Mot1), Ivan Baxter, Balasubramaniam Muthukumar, Hyeong Cheol Park, Peter Buchner, Brett Lahner, John Danku, Keyan Zhao, Joohyun Lee, Malcolm J. Hawkesford, Mary Lou Guerinot, David E. Salt

Dartmouth Scholarship

Molybdenum (Mo) is an essential micronutrient for plants, serving as a cofactor for enzymes involved in nitrate assimilation, sulfite detoxification, abscisic acid biosynthesis, and purine degradation. Here we show that natural variation in shoot Mo content across 92 Arabidopsis thaliana accessions is controlled by variation in a mitochondrially localized transporter (Molybdenum Transporter 1 - MOT1) that belongs to the sulfate transporter superfamily. A deletion in the MOT1 promoter is strongly associated with low shoot Mo, occurring in seven of the accessions with the lowest shoot content of Mo. Consistent with the low Mo phenotype, MOT1 expression in low Mo accessions …

Fully Codon-Optimized Luciferase Uncovers Novel Temperature Characteristics Of The Neurospora Clock, Van D. Gooch, Arun Mehra, Luis F. Larrondo, Julie Fox, Melissa Touroutoutoudis, Jennifer J. Loros, Jay C. Dunlap

Dartmouth Scholarship

We report the complete reconstruction of the firefly luciferase gene, fully codon optimized for expression in Neurospora crassa. This reporter enhances light output by approximately 4 log orders over that with previously available versions, now producing light that is visible to the naked eye and sufficient for monitoring the activities of many poorly expressed genes. Time lapse photography of strains growing in race tubes, in which the frq or eas/ccg-2 promoter is used to drive luciferase, shows the highest levels of luciferase activity near the growth front and newly formed conidial bands. Further, we have established a sorbose medium colony …

Single-Stranded Dna-Binding Proteins Regulate The Abundance Of Lim Domain And Lim Domain-Binding Proteins, Zhixiong Xu, Xianzhang Meng, Ying Cai, Hong Liang, Lalitha Nagarajan, Stephen J Brandt

Student and Faculty Publications

The LIM domain-binding protein Ldb1 is an essential cofactor of LIM-homeodomain (LIM-HD) and LIM-only (LMO) proteins in development. The stoichiometry of Ldb1, LIM-HD, and LMO proteins is tightly controlled in the cell and is likely a critical determinant of their biological actions. Single-stranded DNA-binding proteins (SSBPs) were recently shown to interact with Ldb1 and are also important in developmental programs. We establish here that two mammalian SSBPs, SSBP2 and SSBP3, contribute to an erythroid DNA-binding complex that contains the transcription factors Tal1 and GATA-1, the LIM domain protein Lmo2, and Ldb1 and binds a bipartite E-box-GATA DNA sequence motif. In …

Similar Levels Of X-Linked And Autosomal Nucleotide Variation In African And Non-African Populations Of Drosophila Melanogaster, Nadia D. Singh, J. Michael Macpherson, Jeffrey D. Jensen, Dmitri A. Petrov

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Background: Levels of molecular diversity in Drosophila have repeatedly been shown to be higher in ancestral, African populations than in derived, non-African populations. This pattern holds for both coding and noncoding regions for a variety of molecular markers including single nucleotide polymorphisms and microsatellites. Comparisons of X-linked and autosomal diversity have yielded results largely dependent on population of origin.

Results: In an attempt to further elucidate patterns of sequence diversity in Drosophila melanogaster, we studied nucleotide variation at putatively nonfunctional X-linked and autosomal loci in sub-Saharan African and North American strains of D. melanogaster. We combine our experimental …

A Subset Of Arabidopsis Ap2 Transcription Factors Mediates Cytokinin Responses In Concert With A Two-Component Pathway, Aaron M. Rashotte, Michael G. Mason, Claire E. Hutchison, Fernando J. Ferreira, G. Eric Schaller, Joseph J. Kieber

Dartmouth Scholarship

The plant hormone cytokinin regulates numerous growth and developmental processes. A signal transduction pathway for cytokinin has been elucidated that is similar to bacterial two-component phosphorelays. In Arabidopsis, this pathway is comprised of receptors that are similar to sensor histidine kinases, histidine-containing phosphotransfer proteins, and response regulators (ARRs). There are two classes of response regulators, the type-A ARRs, which act as negative regulators of cytokinin responses, and the type-B ARRs, which are transcription factors that play a positive role in mediating cytokinin-regulated gene expression. Here we show that several closely related members of the Arabidopsis AP2 gene family of …

Saccharomyces Cerevisiae-Based Molecular Tool Kit For Manipulation Of Genes From Gram-Negative Bacteria, Robert M. Q. Shanks, Nicky C. Caiazza, Shannon M. Hinsa, Christine M. Toutain, George A. O'Toole

Dartmouth Scholarship

A tool kit of vectors was designed to manipulate and express genes from a wide range of gram-negative species by using in vivo recombination. Saccharomyces cerevisiae can use its native recombination proteins to combine several amplicons in a single transformation step with high efficiency. We show that this technology is particularly useful for vector design. Shuttle, suicide, and expression vectors useful in a diverse group of bacteria are described and utilized. This report describes the use of these vectors to mutate clpX and clpP of the opportunistic pathogen Pseudomonas aeruginosa and to explore their roles in biofilm formation and surface …