Life Sciences Commons^™

Cytogenetical Studies In Range Grasses Of Iran, M Sheidai, A Tavasoli, P Derakhshandeh

IGC Proceedings (1997-2023)

Cytogenetical and breeding studies of range grasses are in hand. Present article describes preliminary cytogenetical analysis of wheatgrass (Agropyron) and bromegrass (Bromus) taxa (Agropyron trichophorum n = 21, A. pectinoforome n = 21), two different populations of A. repens (n = 28) and Bromus stenostachyus (n = 14). The species varied with regard to chiasma number and distribution. The highest value occurred in A. repens (Mako population). Heterogenity test for the paired samples showed lack of heterogenity for chiasmata indicating homogenity of Agropyron taxa. However a test for ring and rod bivalents showed significant differences …

Meiosis In Budding Yeast, G. Valentin Borner, Andreas Hochwagen, Amy J. Macqueen

Biological, Geological, and Environmental Faculty Publications

Meiosis is a specialized cell division program that is essential for sexual reproduction. The two meiotic divisions reduce chromosome number by half, typically generating haploid genomes that are packaged into gametes. To achieve this ploidy reduction, meiosis relies on highly unusual chromosomal processes including the pairing of homologous chromosomes, assembly of the synaptonemal complex, programmed formation of DNA breaks followed by their processing into crossovers, and the segregation of homologous chromosomes during the first meiotic division. These processes are embedded in a carefully orchestrated cell differentiation program with multiple interdependencies between DNA metabolism, chromosome morphogenesis, and waves of gene expression …

Characterization Of The Immune Deficiency Pathway During Female Meiosis In Drosophila Melanogaster, Sarah Mashburn

College of Science and Health Theses and Dissertations

Organisms can defend against pathogens by significantly increasing the diversity of their progeny, so that some progeny are more likely to survive infection. This led to the prediction that infection should cause an increase in recombination rates which was seen in a previous study. However, the mechanism that regulates recombination rates in response to infection is not understood and in that study they did not provide a mechanism for how that can occur. In an RNAi screen, our lab found the gene mustard (mtd) is required for normal recombination rates. This gene was previously shown to be part of the …

Understanding The Relationship Between B Chromosomes And Nondisjunction In Drosophila Melanogaster, Ayushi Patel

Honors Scholar Theses

B chromosomes are supernumerary, heterochromatic genetic elements that are found in hundreds of different plant and animal species. Recently, B chromosomes were discovered in a stock of Drosophila melanogaster and are carried at a high copy number of 10-12 B chromosomes per cell. B chromosomes are not known to carry any active genes, but when placed in a wild-type genetic background, they cause a significant increase in the frequency of chromosome 4 missegregation during meiosis. This project aimed to understand the relationship between a female’s B chromosome copy number and how often she passes on too many (or too few) …

Estimation Of The Coefficient Of Double-Reduction In Autotetraploid Lucerne, R. Ayadi, P. Barre, Christian Huyghe, B. Julier

IGC Proceedings (1997-2023)

Polyploidy plays an important role in the evolution of species and many cultivated species, particularly in angiosperms, are polyploids (Bever and Felber, 1992; Gallais, 2003). Autopolyploid species that show a tetrasomic inheritance have complex genetics. However, some theoretical models were built for: (1) genetic mapping (Hackett et al., 1998), (2) quantitative genetics (Gallais, 2003) and (3) population genetics (Ronfort et al., 1998). But in practice, most data analyses ignore one essential feature of tetrasomic inheritance that is double-reduction. Indeed, in an autotetraploid species, homologous chromosomes can form tetravalents at meiosis. In this case, a double-reduction is observed if …

Unusual Chromosome Configurations: Evaluation Of Sex Univalent And Trivalent Chromosome Models, Ashley B. Borseth

Master’s Theses

Aneuploidy, or abnormal number of chromosomes in a haploid set, in XY/XX organisms has consequences that can impede physical and cognitive development. To prevent aneuploidy, cellular division relies on the correct position of paired chromosomes and subsequent segregation in the meiotic program. If connections between paired chromosomes sever or errors in chromosome contraction towards spindle poles arise, aneuploidy occurs. Many arthropod species have chromosomes that naturally do not pair, or that pair differently than typical autosomes. Through the evaluation of such systems, novel insights into chromosomal coordination and positioning may be revealed. The objective of this study is twofold: (1) …

The Role Of Cort And Anaphase Promoting Complex/Cyclosome (Apc/C) In Drosophila Sex Determination And Meiosis, Abuzar Sikander Malik

Electronic Theses and Dissertations

The E3 ubiquitin ligase, APC/C, is essential for the completion cell cycle; along with its co-activators it allows mitotic exit and maintenance of G1. APC/C marks various substrates with ubiquitin chains; marked substrates are subsequently destroyed via the 26S proteasome pathway. Cort is a Drosophila female meiosis specific activator of APC/C. Cort works within meiosis in conjunction with Fzy to mediate Securin and cyclin destruction. A C-terminal IR-tail motif and a N-terminal C-box support Cort-APC/C interaction, whereas short motifs like D-box and KEN-box on the target protein impart substrate recognition to Cort. Cort expression is tightly controlled in the female …

Mutations In The N-Terminus Of The Mod(Mdg4) Btb Domain Reveal An Unexpected Role Of Mod(Mdg4) In Chromosome Segregation In Female Meiosis, Gwyneth D E Walker, Bruce D. Mckee

Chancellor’s Honors Program Projects

No abstract provided.

Understanding The Novel Role Of Checkpoint Protein Rough Deal In Homolog Orientation And Centromeric Cohesion In Drosophila Male Meiosis, Qiutao He

Doctoral Dissertations

Meiosis is a central mechanism in sexual reproduction, through which the diploid precursor cells in the germline produce haploid gametes. After fertilization, a new set of diploid genome forms in the offspring with the characteristics of mother and father. The faithful transmission of genetic material to next generation relies on the fidelity of chromosome segregation during meiosis. A variety of mechanisms regulate the chromosome segregations in meiosis, including homolog interaction, chromosome cohesion, and sister-chromatid orientation. In most eukaryotic organisms, homolog interactions are built by the formation of chiasmata resulted from crossovers, but it is absent in male Drosophila in which …

Investigating The Effect Of The Wee-1.3 And Pam-1 Mutations On Meiosis After The Fertilization Of Oocytes In C. Elegans, Sophie Lear, Alex Bender

Biology Presentations

Currently, we are working with two genes: pam-1, which functions in the asymmetric division in meiosis and corresponding polarity, and wee-1.3, which functions in oocyte maturation. The mutation pam-1 is known to disturb embryo viability and reduces the hatch rate to 2% in the worms. However, a rescue mutation, wee-1.3, is known to bring the hatch rate up to 42% because polarity and asymmetry defects are suppressed. From previous research we know that during meiosis, the pam-1 mutation results in meiotic exit delays and other mutant phenotypes such as failure of meiosis II. Currently, we are imaging …

Opinion: Genetic Conflict With Mobile Elements Drives Eukaryotic Genome Evolution, And Perhaps Also Eukaryogenesis, Adena B. Collens, Laura A. Katz

Biological Sciences: Faculty Publications

Through analyses of diverse microeukaryotes, we have previously argued that eukaryotic genomes are dynamic systems that rely on epigenetic mechanisms to distinguish germline (i.e., DNA to be inherited) from soma (i.e., DNA that undergoes polyploidization, genome rearrangement, etc.), even in the context of a single nucleus. Here, we extend these arguments by including two well-documented observations: (1) eukaryotic genomes interact frequently with mobile genetic elements (MGEs) like viruses and transposable elements (TEs), creating genetic conflict, and (2) epigenetic mechanisms regulate MGEs. Synthesis of these ideas leads to the hypothesis that genetic conflict with MGEs contributed to the evolution of a …

Effects Of Aurora Kinase C Expression On Retina Pigmented Epithelial Cell Migration, Proliferation, And Anchorage Independent Growth, Justin Bejar

Seton Hall University Dissertations and Theses (ETDs)

Cancer is a common and deadly disease in the United States with 1,806,590 new cancer cases in 2019 and 606,520 cancer deaths projected in 2020. These deaths are primarily due to the uncontrolled cell proliferation and migratory nature of the disease. Many cancer cells express genes normally restricted to meiotic cells. For example, Aurora Kinase C (AURKC) is known to regulate chromosome segregation in meiotic cells yet it is expressed in many different types of cancer, such as breast, prostate, colorectal, liver, cervical, thyroid, and testicular cancers. As a means to study the function of AURKC, an …

Seasonal Expression Of Apospory In Bahiagrass, Esteban F. Rios, Ann R. Blount, Kevin E. Kenworthy, Carlos A. Acuña, Kenneth H. Quesenberry

IGC Proceedings (1997-2023)

Flowering plants can reproduce sexually (outcrossing and/or selfing) and/or asexually. Sexual reproduction implies the successful completion of meiosis and double fertilisation for the formation of both the embryo and the endosperm. In contrast, gametophytic apomixis is an asexual mode of reproduction through seeds that involves parthenogenetic embryo development from a cytologically unreduced egg cell (2n). Apospory is the process by which unreduced gametophytes are formed after a series of mitotic divisions of somatic cells (2n) in the ovary. This occurs independently from the sexual meiotic process; and therefore, both sexual and apomictic pathways may coexist simultaneously. Apospory is inherited in …

Ywha (14-3-3) Protein Isoforms And Their Interactions With Cdc25b Phosphatase In Mouse Oogenesis And Oocyte Maturation, Alaa A. Eisa, Santanu De, Ariana Detwiler, Eva Gilker, Alexander C. Ignatious, Srinivasan Vijayaraghavan, Douglas Kline

Biology Faculty Articles

Background

Immature mammalian oocytes are held arrested at prophase I of meiosis by an inhibitory phosphorylation of cyclin-dependent kinase 1 (CDK1). Release from this meiotic arrest and germinal vesicle breakdown is dependent on dephosphorylation of CDK1 by the protein, cell cycle division 25B (CDC25B). Evidence suggests that phosphorylated CDC25B is bound to YWHA (14-3-3) proteins in the cytoplasm of immature oocytes and is thus maintained in an inactive form. The importance of YWHA in meiosis demands additional studies.

Results

Messenger RNA for multiple isoforms of the YWHA protein family was detected in mouse oocytes and eggs. All seven mammalian YWHA …

From Single Cells To Human Disease: High-Resolution Phenotyping Of Male Infertility Models Using Single-Cell Rna Sequencing, Min Jung

Arts & Sciences Electronic Theses and Dissertations

Male infertility is a complex disease that can result in significant emotional distress and treatment costs. Globally, male infertility affects 7% of males, and while its incidence is rising, its etiology remains elusive. In order to improve patient care, it is critical to identify the nature of spermatogenic failure in as many men as possible. The extensive cellular heterogeneity of testis has limited the application of bulk expression measurements to capture crucial information to dissect molecular mechanisms of defects in the infertile patients. Thus, the application of single-cell RNA-sequencing on male germ cells provides an amazing new set of scientific …

Higher Order Chromosome Organization And Recombination Dynamics Of Meiotic Prophase I In Mouse Spermatocytes, Rhea Kang

Dissertations & Theses (Open Access)

Meiotic recombination is required for parental chromosomes to find each other (pairing/synapsis) and to exchange genetic information thus allowing faithful segregation of chromosomes and the production of haploid gametes. At the start of meiotic prophase I, meiotic chromosomes organize into loop arrays that extrude out of the chromosome axis. Then, a large number of programmed double-strand breaks (DSBs) are formed at specific chromosomal locations or “hotspots” on parental chromosomes, which are repaired by homologous recombination (HR). HR produces either crossovers, which result in the exchange of flanking markers between homologs, or noncrossovers, which are short regions ofgene conversion to the …

The Roles Of Tid1, Ndj1, And Spo16 In Distributive Segregation During Saccharomyces Cerevisiae Meiosis, Ethan Atticus Shaw

Master's Theses

Meiosis is a specialized form of cell division in sexually reproducing eukaryotes. Crossovers are physical connections formed between homologous chromosomes during meiosis; these connections help ensure normal segregation of homologous chromosomes at meiosis I. However, the yeast Saccharomyces cerevisiae and other eukaryotes can still segregate homologs properly even in the absence of some crossovers. This is due to a backup mechanism known as distributive segregation, which correctly segregates non-crossover chromosomes at a higher rate than if segregation were completely random. To study distributive segregation, we have generated diploid yeast with one homeologous chromosome pair consisting of a Saccharomyces cerevisiae chromosome …

Computational Insights Into The Generation Of Chromosomal Copy Number Changes, Yihua Liu

Dissertations & Theses (Open Access)

Deviations from a diploid configuration of the human genome, spanning single genes or entire chromosomes, can have wide-ranging impacts on the variation of human phenotypes, including Mendelian and complex forms of diseases. These chromosomal alterations — such as duplications, deletions or copy-neutral loss-of-heterozygosity — are thus important forms of genetic variation for phenotyping populations of individuals as well as populations of cells. Indeed, copy number variants (CNVs) serve as hallmarks of critical changes in the development of particular diseases such as cancer and thus may be used as biomarkers. These CNVs may be either inherited (transmitted by germ cells, originating …

Comparative Meiotic Cytology Among Drosophila Species, Ahmed Folademi Majekodunmi

College of Science and Health Theses and Dissertations

Physical connections established by homologous recombination are normally sufficient to establish proper co-orientation of chromosomes during prometaphase of female meiosis I. Nonexchange chromosomes can still segregate because they are connected by heterochromatic threads, which are thought to connect homologous chromosomes and ensure co-orientation in the absence of a chiasma. In Drosophila, the nonexchange chromosomes (such as the Muller F element, also called the “dot chromosome,” which never undergoes recombination) move out on the spindle during prometaphase I, and can be found positioned between the spindle poles and the exchange chromosomes at the metaphase plate. By metaphase I arrest, these …

Elucidating The Molecular Parameters And Mechanism Of Homology Searching During Meiosis In Neurospora Crassa, Nicholas Adam Rhoades

Theses and Dissertations

Integration of foreign DNA into a host genome is often detrimental to the host organism, as the DNA is often of viral or transposon origin. Many organisms have established DNA surveillance and genome integrity mechanisms to defend against these harmful DNA insertions. Neurospora crassa, a filamentous fungus belonging to the Ascomycota group, has several DNA defense mechanisms to combat foreign DNA integration to its genome. One such mechanism is Meiotic Silencing of Unpaired DNA (MSUD). During meiosis, this remarkable system can detect unpaired genes on homologous chromosomes during sexual reproduction and silence their expression throughout meiosis. In order for the …

A Linkage Map For The Newt Notophthalmus Viridescens: Insights In Vertebrate Genome And Chromosome Evolution, Melissa C. Keinath, S. Randal Voss, Panagiotis A. Tsonis, Jeramiah J. Smith

Biology Faculty Publications

Genetic linkage maps are fundamental resources that enable diverse genetic and genomic approaches, including quantitative trait locus (QTL) analyses and comparative studies of genome evolution. It is straightforward to build linkage maps for species that are amenable to laboratory culture and genetic crossing designs, and that have relatively small genomes and few chromosomes. It is more difficult to generate linkage maps for species that do not meet these criteria. Here, we introduce a method to rapidly build linkage maps for salamanders, which are known for their enormous genome sizes. As proof of principle, we developed a linkage map with thousands …

Cellular/Molecular Analysis Of Interspecies Sterile Male Hybrids In Drosophila, Rachelle L. Kanippayoor

Electronic Thesis and Dissertation Repository

Over time, genetic differences can accumulate between populations that are geographically separated. This genetic divergence can lead to the evolution of reproductive isolating mechanisms that reduce gene flow between the populations and, upon secondary contact, result in distinct species. The process of speciation is, thus, what accounts for the multitude of species that contribute to the rich biodiversity on Earth. Interspecies hybrid sterility is a postzygotic isolating mechanism that affects the development of hybrids, rendering them sterile. A notable trend, known as Haldane's Rule, describes that heterogametic individual (e.g. males in Drosophila) are more susceptible to sterility than homogametic …

Identification Of Novel Nuclear Proteins Required For Meiotic Silencing By Unpaired Dna In Neurospora Crassa, Dilini Ralalage

Theses and Dissertations

A fundamental step that occurs during sexual reproduction is meiosis, which is a specialized type of cell division. During meiosis, pairs of chromosomes exchange genetic information via recombination. At this point, the genome is particularly susceptible to viruses and other foreign genetic invasions. Therefore, it is important to protect the genome to prevent the transmission of foreign genetic materials to the offspring. There are several mechanisms work together to protect host genome from foreign genetic materials. These are known as “genome defense mechanisms”.

The fungus Neurospora crassa is one of the best organisms for genome defense studies due to the …

Amoebozoans Are Secretly But Ancestrally Sexual: Evidence For Sex Genes And Potential Novel Crossover Pathways In Diverse Groups Of Amoebae, Yonas I. Tekle, Fiona C. Wood, Laura A. Katz, Mario A. Cero ́ N-Romero, Lydia A. Gorfu

Biological Sciences: Faculty Publications

Sex is beneficial in eukaryotes as it can increase genetic diversity, reshuffle their genomes, and purge deleterious mutations. Yet, its evolution remains a mystery. The eukaryotic clade supergroup Amoebozoa encompasses diverse lineages of polymorphic amoeboid forms, including both free-living and parasitic lineages. The group is generally believed to be asexual, though recent studies show that some of its members are implicated in cryptic forms of sexual cycles. In this study, we conduct a comprehensive inventory and analysis of genes involved in meiosis and related processes, in order to investigate the evolutionary history of sex in the clade. We analyzed genomic …

Pollen Viability And Meiotic Abnormalities In Brome Grasses(Bromus L., Section Ceratochloa) From Argentina, Gabriela Leofanti, Elsa Lucila Camadro

Turkish Journal of Botany

Bromus Section Ceratochloa includes temperate forage species. South American species form a morphologically very variable hexaploid complex (2n = 6x = 42), with a controversial taxonomic classification. Reproductive biology has been studied in several of them, but the number of analyzed plants has seldom been reported. Further investigations might clarify breeding relations and the adequacy of current classifications. Pollen viability and size, which can provide evidence of spontaneous hybridization, were studied in seven accessions (six plants/accession) classified as B. catharticus var. catharticus, var. elata, and var. rupestris; B. parodii; B. bonariensis; B. lithobius; and B. coloratus. Variability was detected among …

Functions Of Atr/Mec1 In Meiosis And The Cell Cycle, Layne Weatherford

Wayne State University Dissertations

Mec1 is a protein kinase in S. cerevisiae that is critical for the DNA damage checkpoint response, and is the yeast orthologue of the human ATR protein. Cancer cells rely on ATR to arrest the cell cycle and allow sufficient time to repair DNA damage before proceeding through the cell cycle, and ATR inhibitors have been developed as possible anti-cancer agents. DBF4 is the regulatory subunit of DBF4-dependent kinase (DDK) that regulates initiation of DNA replication and is overexpressed in a number of different cancer types. To better understand ATR and DBF4 function, we took advantage of yeast genetics to …

Patchiness Of Ciliate Communities Sampled At Varying Spatial Scales Along The New England Shelf, Jean-David Grattepanche, George B. Mcmanus, Laura A. Katz

Biological Sciences: Faculty Publications

Although protists (microbial eukaryotes) provide an important link between bacteria and Metazoa in food webs, we do not yet have a clear understanding of the spatial scales on which protist diversity varies. Here, we use a combination of DNA fingerprinting (denaturant gradient gel electrophoresis or DGGE) and high-throughput sequencing (HTS) to assess the ciliate community in the class Spirotrichea at varying scales of 1–3 km sampled in three locations separated by at least 25 km—offshore, midshelf and inshore—along the New England shelf. Analyses of both abundant community (DGGE) and the total community (HTS) members reveal that: 1) ciliate communities are …

Cohesion Without Cohesins In Drosophila Meiosis, Avik Mukherjee

Doctoral Dissertations

Meiosis is essential for sexual reproduction. The proper segregation of chromosomes in meiosis requires multiple functions of a multi-subunit protein complex known as cohesin. Cohesin forms a ring around duplicated sister chromatids and prevents them from separating prematurely. In Drosophila, mitotic cohesin is composed of four subunits: SMC1 and SMC3 and SCC1/RAD21 and SCC3/SA and are required for mitotic cohesion. However, RAD21 is dispensable for meiotic cohesion and although SMC1 and SMC3 are present on meiotic centromeres and on synapsed chromosome arms, as expected, their functions in meiosis remain poorly characterized. Moreover, unlike in other eukaryotes in which screens for …

Oxidative Stress In Oocytes During Midprophase Induces Premature Loss Of Cohesion And Chromosome Segregation Errors, Adrienne T. Perkins, Thomas M. Das, Lauren C. Panzera, Sharon E. Bickel

Dartmouth Scholarship

In humans, errors in meiotic chromosome segregation that produce aneuploid gametes increase dramatically as women age, a phenomenon termed the "maternal age effect." During meiosis, cohesion between sister chromatids keeps recombinant homologs physically attached and premature loss of cohesion can lead to missegregation of homologs during meiosis I. A growing body of evidence suggests that meiotic cohesion deteriorates as oocytes age and contributes to the maternal age effect. One hallmark of aging cells is an increase in oxidative damage caused by reactive oxygen species (ROS). Therefore, increased oxidative damage in older oocytes may be one of the factors that leads …

The Fast-Evolving Phy-2 Gene Modulates Sexual Development In Response To Light In The Model Fungus Neurospora Crassa, Zheng Wang, Ning Li, Jigang Li, Jay C. Dunlap, Frances Trail, Jeffrey P. Townsend

Dartmouth Scholarship

Rapid responses to changes in incident light are critical to the guidance of behavior and development in most species. Phytochrome light receptors in particular play key roles in bacterial physiology and plant development, but their functions and regulation are less well understood in fungi. Nevertheless, genome-wide expression measurements provide key information that can guide experiments that reveal how genes respond to environmental signals and clarify their role in development. We performed functional genomic and phenotypic analyses of the two phytochromes in Neurospora crassa, a fungal model adapted to a postfire environment that experiences dramatically variable light conditions. Expression of phy-1 …