Open Access. Powered by Scholars. Published by Universities.®

Genetics Commons™

Open Access. Powered by Scholars. Published by Universities.®

University of Arkansas, Fayetteville

Discipline
Keyword
Publication Year
Publication
Publication Type

Articles 61 - 90 of 90

Full-Text Articles in Genetics

Identification Of Biomarkers Associated With Rous Sarcoma Virus-Induced Tumors In Two Divergently Selected Chicken Lines, Ashley Hayden Aug 2016

Identification Of Biomarkers Associated With Rous Sarcoma Virus-Induced Tumors In Two Divergently Selected Chicken Lines, Ashley Hayden

Graduate Theses and Dissertations

Poultry has become especially important to genetic research due to breeding feasibility, short generation turnover, and ease of maintaining large populations. The discovery of virus induced cancer has paved the way for further genetic studies. Rous Sarcoma Virus (RSV) is a tumor-causing virus that infects poultry. While not prevalent today, it can serve as a model for virus-induced cancer in humans and create additional insight to marker assisted selection in poultry. Genetically selected Arkansas Progressor (AP) and Arkansas Regressor (AR) chicken lines have been established and maintained at the Arkansas Experimental Station (AES) in Fayetteville, AR. Previous research has investigated …


Characterization Of Broiler Lines Divergently Selected For Breast Muscle Color, Sara Katherine Orlowski Aug 2016

Characterization Of Broiler Lines Divergently Selected For Breast Muscle Color, Sara Katherine Orlowski

Graduate Theses and Dissertations

An increase in the consumption of poultry has generated an increase in demand for higher yielding broilers. This has led to an increase in atypical meat and issues with appearance. Color is a direct result of a pH decline as meat goes through rigor mortis with meat generally becoming lighter. If the pH declines too rapidly or too slowly, meat quality can suffer. Physical properties of meat can be altered by pH. A fast pH decline results in pale meat with decreased tenderness. A slow pH decline can result in darker meat with a reduced shelf-life. With a known relationship …


Associations Of Single Nucleotide Polymorphisms In The Bovine Prolactin, Melatonin Receptor 1a, And Dopamine Receptor D2 Genes With Hair Coat Shedding Scores And Productivity Traits In Beef Cattle, Laura R. Meyer Aug 2016

Associations Of Single Nucleotide Polymorphisms In The Bovine Prolactin, Melatonin Receptor 1a, And Dopamine Receptor D2 Genes With Hair Coat Shedding Scores And Productivity Traits In Beef Cattle, Laura R. Meyer

Graduate Theses and Dissertations

Calving rate is a qualitative trait regulated by several genes and is strongly affected by the environment. With the development of biotechnology and gene identification, scientists are able to determine which genes affect these productivity traits to improve accurate selection decisions. Prolactin (PRL) has been associated with reproductive traits, melatonin receptor 1a (MTNR1A) has been associated with meat quality traits, and the dopamine receptor D2 (DRD2) gene has been associated with hair coat score (HCS) in cattle. Our objective was to determine associations between mutations in the PRL, MTNR1A, and DRD2 genes and cow-calf profitability traits. Genomic DNA was extracted …


Identification Of Biomarkers For The Overall Survival Of Ovarian Cancer Patients, Kristi Mai May 2016

Identification Of Biomarkers For The Overall Survival Of Ovarian Cancer Patients, Kristi Mai

Graduate Theses and Dissertations

Rapid advance in sequencing technology has led to genome-wide analysis of genetic and epigenetic features simultaneously, making it possible to understand the biological mechanisms underlying cancer initiation and progression. However, how to identify important prognostic features poses a great challenge for both statistical modeling and computing. In this thesis, a network-based approach is applied to the Cancer Genome Atlas (TCGA) ovarian cancer data to identify important genes related to the overall survival of ovarian cancer patients. In the first step, a stepwise correlation-based selector is used to reduce the dimensionality of TCGA data, by filtering out a large number of …


Genetic Variation And Species Distribution Of Subterranean Termites In The Southeastern U.S. Focusing On Family Structure And The Invasive Formosan Subterranean Termite, Mark Allan Janowiecki Jul 2015

Genetic Variation And Species Distribution Of Subterranean Termites In The Southeastern U.S. Focusing On Family Structure And The Invasive Formosan Subterranean Termite, Mark Allan Janowiecki

Graduate Theses and Dissertations

This work applies molecular genetic tools to distinguish the identity and understand the biology of termites, particularly Reticulitermes Holmgren and Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae) in the southeastern U.S. Termites are important economic pests costing billions of dollars annually to Americans but also are important wood decomposers in natural settings. Molecular tools are essential for species identification because of the morphological ambiguities among species. The cryptic nest structure of subterranean termites which prevents adequate sampling makes molecular genetic tools essential to examine an entire colony.

A molecular diagnostic technique was created to differentiate Coptotermes formosanus, an invasive species in the …


Population Structure Of Central Stoneroller (Campostoma Anomalum) On The Ozark Plateau In Arkansas And Missouri, Mallory Jane Jeffers Jul 2015

Population Structure Of Central Stoneroller (Campostoma Anomalum) On The Ozark Plateau In Arkansas And Missouri, Mallory Jane Jeffers

Graduate Theses and Dissertations

Stream fishes on the Ozark Plateau have been influenced both by historic events (i.e. vicariance versus dispersal) and ecological forces (i.e. flow regime). To examine the role of these processes, genetic structure of Central Stoneroller (Campostoma anomalum), an ecologically important omnivorous minnow with a broad distribution and elevated abundance, was evaluated across populations in the White River drainage of the Ozark Plateau in Arkansas and Missouri. Fin clips of five to eight individuals were taken at each of 20 sites (N=138 individuals; average=6.9), selected so as to represent two different flow regimes: intermittently flashy (N=10 sites; N=73 individuals; average=7.3/ site) …


A Phylogenetic Analysis Of Dictyostelium Purpureum Based On Nuclear Rdna Sequences, Mahmoud Suliman May 2015

A Phylogenetic Analysis Of Dictyostelium Purpureum Based On Nuclear Rdna Sequences, Mahmoud Suliman

Graduate Theses and Dissertations

Dictyostelids (cellular slime molds) are eukaryotic microorganisms that have both unicellular and multicellular stages during their life cycle. In this study, a molecular phylogenetic analysis was conducted for isolates of one species (Dictyostelium purpureum) based DNA sequences of the ITS, 5.8S and SSU regions of nuclear rDNA. Moreover, a detailed morphological study was carried out using images obtained with both dissecting and compound microscopes. Mating experiments were carried out to assess macrocysts formation between each pair of isolates. The constructed molecular phylogenetic trees indicate that (1) D. purpureum isolates are more closely related to each other than to other species …


Divergent Selection For Four-Day Relative Breast Yield And The Effect Of Thermal Manipulations On Growth Characteristics On Lines Selected For Different Processing Dates., James Grant Mason May 2015

Divergent Selection For Four-Day Relative Breast Yield And The Effect Of Thermal Manipulations On Growth Characteristics On Lines Selected For Different Processing Dates., James Grant Mason

Graduate Theses and Dissertations

Genetic selections currently utilized in the poultry industry have been highly successful in promoting broiler growth rate and yield. However, these selections may have come at the expense of broiler physiology, as evidenced by an increase in physiological disorders. To address this experimentation was undergone to develop a novel method of selection to promote growth with minimal physiological impact and to assess how a new embryonic technique affects growth in broiler lines exhibiting different growth rates.

In the first experiment, a random bred control (RAN) broiler line was divergently selected for four-day relative breast yield (BY4) resulting in the high …


Construction Of 3d Biomimetic Tissue Niches For Directing Pancreatic Lineage Differentiation Of Human Embryonic Stem Cells, Weiwei Wang Aug 2014

Construction Of 3d Biomimetic Tissue Niches For Directing Pancreatic Lineage Differentiation Of Human Embryonic Stem Cells, Weiwei Wang

Graduate Theses and Dissertations

The potential of human embryonic stem cells (hESCs) to differentiate into insulin producing beta cells offers great hope for cell-based therapy for diabetes treatment. However, in vitro pancreatic differentiation of hESCs remains challenging. In the past decade, most protocols for differentiating pancreatic cells have been focused on the use of signaling molecule cocktails on 2D substrates. Studies on embryonic development biology strongly suggest that extracellular matrix (ECM) plays a critical role on hESCs behavior. In this work, we first established a 3D collagen scaffold culture system for hESCs differentiating into definitive endoderm (DE), which is the first and most important …


The Role Of Histone H3 And H4 In Centromere Function And Genome Integrity, Payel Chaudhuri Dec 2013

The Role Of Histone H3 And H4 In Centromere Function And Genome Integrity, Payel Chaudhuri

Graduate Theses and Dissertations

Histone H2A plays an important role in chromosomal segregation among parent and daughter cells during mitosis. While it is established that this histone is important in maintaining chromosome number in cell, further work is carried out to explore the role of other histones like H3 and H4 for similar effects. A systematic study is initiated by screening a library based on mutation of different amino acid residues in these histones. This detailed screening identified specific regions within H3 and H4, which are critically important for centromeric function. These histones residing near the DNA entry/exit region of nucleosome effects the functionality …


Effects Of Ergot Alkaloids And Bovine Bodily Fluids On Cytochrome P450 Activity, Nicholas Scott Ezell May 2013

Effects Of Ergot Alkaloids And Bovine Bodily Fluids On Cytochrome P450 Activity, Nicholas Scott Ezell

Graduate Theses and Dissertations

This thesis evaluates the PromegaTM P450-Glo assay (PromegaTM V9800) as a tool for quantifying ergot alkaloid concentration. Current techniques used for detection of ergot alkaloids are slow and expensive, do not detect all ergot alkaloids, or are not effective on bovine bodily fluids. The first study was conducted to determine effects of commercial ergot alkaloids (n = 6; 0 - 400 μM) on the PromegaTM P450-Glo assay. Cytochrome P450 (CYP450) activity in assay had a differential response to each ergot alkaloid and concentration. As concentrations of ergotamine, dihydroergotamine, ergocornine, and ergocryptine increased CYP450 activity was inhibited (P …


Diversity, Identification, Mapping And Pyramiding Of Genes For Resistance To Soybean Mosaic Virus [Glycine Max (L.) Merr.], Innan Gloria Cervantes Martinez May 2012

Diversity, Identification, Mapping And Pyramiding Of Genes For Resistance To Soybean Mosaic Virus [Glycine Max (L.) Merr.], Innan Gloria Cervantes Martinez

Graduate Theses and Dissertations

Soybean Mosaic Virus (SMV) is a prevalent viral pathogen transmitted by aphids and via seed, causing significant yield loss and quality reduction. There are seven SMV strain groups (G1 to G7) and three resistance loci( Rsv1, Rsv3, and Rsv4) reported in soybean. New sources of SMV resistance would be valuable for breeding cultivars with durable resistance to multiple strains. The objectives of this research were to analyze genetic diversity of SMV-resistant soybean germplasm at the molecular level; to pyramid three genes from different sources for durable SMV resistance; and to identify and map new genes/alleles for differential reactions to SMV …


The Incidence Of Plexiform Lesion Formation In Lines Divergently Selected For Ascites, James Grant Mason Dec 2011

The Incidence Of Plexiform Lesion Formation In Lines Divergently Selected For Ascites, James Grant Mason

Graduate Theses and Dissertations

Complex Vascular Lesions, (CVL) are a common vascular change associated with idiopathicpulmonary arterial hypertension (IPAH). CVL have been characterized in studies using animal models involving, but not limited to, Sprague-Dawley rats and poultry (Abe et al., 2010; Wideman et al., 2011).IPAH has been documented in poultry although no connection has been made with CVLs. The current study characterizes CVL in the lungs from broilers derived from lines divergently selected for 15 generations for ascites susceptibility under conditions of simulated high altitude. The ascites RES and SUS lines were sampled for CVL incidence over time. Both lines were reared in a …


Effects Of Osteopontin Single Nucleotide Polymorphisms On Bull Semen Quality, Chance L. Williams Aug 2011

Effects Of Osteopontin Single Nucleotide Polymorphisms On Bull Semen Quality, Chance L. Williams

Graduate Theses and Dissertations

Two groups of bulls were utilized to evaluate if single nucleotide polymorphisms (SNP) in the Bos taurus OPN gene (GenBank accession # AY878328.1) promoter region were related to bull semen quality variables as evaluated by computer assisted semen analysis (CASA). Group 1 consisted of 19 Angus and Balancer bulls, ranging in age from 5 to 8 years, which were collected weekly during a 2-month period (July 15, 2010 through September 19, 2010). Group 2 consisted of 16 Brahman influenced (1/8 to 3/16 Brahman) bulls, mean age = 1.1 ± 0.1 year, that were collected monthly for a 7 month period …


A Novel Gene Silencing Vector For Plant Genomics And Biotechnology, Dustin Hoover, Scott Nicholson, Vibha Srivastava Jan 2011

A Novel Gene Silencing Vector For Plant Genomics And Biotechnology, Dustin Hoover, Scott Nicholson, Vibha Srivastava

Discovery, The Student Journal of Dale Bumpers College of Agricultural, Food and Life Sciences

Gene silencing is a process of suppressing activity of specific genes by producing “interfering” RNA encoded by foreign genes. This process serves as the principle of genetic modification in plants and animals, which is an important tool in genomics and biotechnology, allowing scientists to manipulate organisms to better meet human demands. New approaches of gene silencing may enable improvements on current practices of genetic modification, and broaden the application and impact of gene silencing in biotechnology. Recently, a novel vector design consisting of the transcription of short gene fragments lacking transcription termination signals was demonstrated to be effective in partial …


Applications Of Variable Number Tandem Repeat Genotyping In The Validation Of An Animal Medical Model And Gene Flow Studies In Threatened Populations Of Reptiles, Candace D. Smith Dec 2009

Applications Of Variable Number Tandem Repeat Genotyping In The Validation Of An Animal Medical Model And Gene Flow Studies In Threatened Populations Of Reptiles, Candace D. Smith

Graduate Theses and Dissertations

We used variable number tandem repeats (VNTR) to validate the chicken as a human medical model for Pulmonary Arterial Hypertension. We identified seven regions on four chromosomes and interrogated for VNTR markers that significantly associate with Pulmonary Hypertension Syndrome/ascites. In those regions, we identified 7 candidate genes; AGTR1, ACE, p38MAPK, SST, 5HT2B, NET1, and CALM3 for further analysis as significantly contributing QTL for ascites/PHS. We also used variable number tandem repeats to measure gene flow and gather evidence for multiple paternity in a population of Timber rattlesnakes, Crotalus horridus. We were able to verify 1 VNTR that can be used …


Letter From The Dean, Lalit Verma Jan 2009

Letter From The Dean, Lalit Verma

Discovery, The Student Journal of Dale Bumpers College of Agricultural, Food and Life Sciences

No abstract provided.


Dna Sequence Of Melanocortin 1-Receptor Gene In Coturnix Japonica: Correlation With Three E Locus Alleles, E, E+, Erh, Rupali B. Ugrankar Jan 2003

Dna Sequence Of Melanocortin 1-Receptor Gene In Coturnix Japonica: Correlation With Three E Locus Alleles, E, E+, Erh, Rupali B. Ugrankar

Inquiry: The University of Arkansas Undergraduate Research Journal

The melanocortin 1-receptor (MC1-R) gene plays a key role in the expression of fur and feather color in mammals and birds by regulating the distribution of two melanin pigments: eumelanin (black/brown) and pheomelanin (red/yellow). MC1-R corresponds to the classical Extension (E) locus in mice, pigs, dogs, horses, and chickens. Three E locus alleles, the wild-type (e + ), brown (E), and redhead (e rh) have been identified in Japanese quail (Coturnix japonica). To determine if the quail E locus phenotypes were due to variation in the MC1-R gene, the coding region of the MC1-R gene was PCR amplified and DNA …


Dna Sequence Of Melanocortin 1-Receptor Gene In Coturnix Japonica: Correlation With Three E Locus Alleles—E,E+, And Erh, Rupali Ugrankar, Kim Cheng, Ronald Okimoto Jan 2003

Dna Sequence Of Melanocortin 1-Receptor Gene In Coturnix Japonica: Correlation With Three E Locus Alleles—E,E+, And Erh, Rupali Ugrankar, Kim Cheng, Ronald Okimoto

Discovery, The Student Journal of Dale Bumpers College of Agricultural, Food and Life Sciences

The melanocortin 1-receptor (MC1-R) gene plays a key role in the expression of fur and feather color in mammals and birds by regulating the distribution of two melanin pigments: eumelanin (black/brown) and pheomelanin (red/yellow). MC1-R corresponds to the classical Extension (E) locus in mice, pigs, dogs, horses, and chickens. Three E locus alleles, the wild-type (e+), brown (E), and redhead (erh) have been identified in Japanese quail (Coturnix japonica). To determine if the quail E locus phenotypes were due to variation in the MC1-R gene, the coding region of the MC1-R gene was PCR amplified and DNA sequenced using genomic …


Photoreactivation Of Lethal Damage Induced In Hamster X Xenopus Hybrid Cells And Their Parentals By Uv Light, David Bohlender, Stuart Williams, Emir Cruz, H. Gaston Griggs Jan 1987

Photoreactivation Of Lethal Damage Induced In Hamster X Xenopus Hybrid Cells And Their Parentals By Uv Light, David Bohlender, Stuart Williams, Emir Cruz, H. Gaston Griggs

Journal of the Arkansas Academy of Science

A85 Xenopus cells that exhibited a high level of photoreactivation (PR) and V79B2 hamster cells that exhibited little PR were fused to produce the V79B2 x A85 cell line — a hybrid line which possessed a relatively stable karyotype, with most cells containing the entire V79B2 and A85 genomes. UV and UV plus PR fluence-survival relations were then determined and compared for the hybrid and parental lines in a first attempt to elucidate interactions of the parental PR mechanisms in the hybrid. It was anticipated that the A85 genome in the hybrid would produce PR enzyme in sufficient concentration and …


Ultraviolet Light Reactivation Of Gamma-Ray Induces Chromosome Aberrations In G1 Phase Xenopus Cells, Susan Kulp, Linda Rogers, H. Gaston Griggs Jan 1984

Ultraviolet Light Reactivation Of Gamma-Ray Induces Chromosome Aberrations In G1 Phase Xenopus Cells, Susan Kulp, Linda Rogers, H. Gaston Griggs

Journal of the Arkansas Academy of Science

No abstract provided.


Heterochromatic Patterns In Drosophila Virilis Interphase Nuclei, William C. Guest Jan 1980

Heterochromatic Patterns In Drosophila Virilis Interphase Nuclei, William C. Guest

Journal of the Arkansas Academy of Science

No abstract provided.


Some Effects Of Methyl Green On Expression Of Damage Induced In G1 Xenopus Cells By Ultraviolet Light, Keith E. Mathias, H. Gaston Griggs Jan 1980

Some Effects Of Methyl Green On Expression Of Damage Induced In G1 Xenopus Cells By Ultraviolet Light, Keith E. Mathias, H. Gaston Griggs

Journal of the Arkansas Academy of Science

No abstract provided.


Electrophoretic Analysis Of Blood Serum Proteins In Three Species Of Water Snakes (Genus Nerodia), Phyllis J. Garnett Jan 1979

Electrophoretic Analysis Of Blood Serum Proteins In Three Species Of Water Snakes (Genus Nerodia), Phyllis J. Garnett

Journal of the Arkansas Academy of Science

Serum from three species of water snakes (Nerodia rhombifera, N. erythrogaster and N. fasciata) from one geographic region was analyzed electrophoretically on cellulose acetate, and anodic mobility and relative concentration of the fractions were determined by a recording densitometer with an automatic integrator. Classification of fractions was based on mobility (Rf, values), and for identification purposes, bands were labeled in order of decreasing mobility (albumin and alpha₁, alpha₂, alpha₃, beta₁, beta₂, gamma₁, and gamma₂ globulins). Seven fractions were identified in each species with alpha₃ being absent from N. rhombifera and N. erythrogaster, and only one gamma fraction was observed in …


Genic Variation In White-Tailed Deer From Arkansas, Phyllis K. Price, Michael E. Cartwright, Mitchell J. Rogers Jan 1979

Genic Variation In White-Tailed Deer From Arkansas, Phyllis K. Price, Michael E. Cartwright, Mitchell J. Rogers

Journal of the Arkansas Academy of Science

Liver and kidney samples of 33 white-tailed deer (Odocoileus virginianus) representing three populations in Arkansas were examined with horizontal starch gel electrophoresis. Of 17 loci examined, only PGM-1 and ES-2 exhibited polymorphism. Average individual heterozygosity, ranging from 2.3% to 4.7% with a mean of 3.1 %, was much lower than that reported for white-tailed deer in other parts of its range. The three populations examined in this study were highly similar based on Rogers' genetic similarity coefficient.


Time Course Of Pr Of Uv-Induced Chromosomal Aberrations And Lethal Damage In G1 Xenopus Cells, Jan Payne, H. Gaston Griggs Jan 1977

Time Course Of Pr Of Uv-Induced Chromosomal Aberrations And Lethal Damage In G1 Xenopus Cells, Jan Payne, H. Gaston Griggs

Journal of the Arkansas Academy of Science

Synchronous cultures of early G1 cells were exposed to UV and their ability to photoreactivate lethal and aberrational damage was determined as a function of time following UV exposure. Lesions leading to cell death were converted to a non-photoreactivable state before cells entered S phase, while lesions leading to chromosomal aberrations were converted to a non-photoreactivable state as the cells entered S phase. These results indicate that the intracellular mechanism which expresses photoreactivable UV-induced lesions in G1 cells as cell death is not identical to the mechanism which expresses such lesions as chromosomal aberrations, and the two mechanisms operate primarily …


Study Of Ultraviolet-Induces Chromatid And Chromosome Aberrations As A Function Of Dose In G1 Phase Vertebrate Tissue Cultures, Troy V. Orr, H. Gaston Griggs Jan 1976

Study Of Ultraviolet-Induces Chromatid And Chromosome Aberrations As A Function Of Dose In G1 Phase Vertebrate Tissue Cultures, Troy V. Orr, H. Gaston Griggs

Journal of the Arkansas Academy of Science

G1 phase A8 Xenopus laevis (toad) and V79B Cricetulus griseus (hamster) tissue cultures were used to observe the frequency of ultraviolet-induced chromosomal aberrations as a function of dose. When cultures are irradiated with ultraviolet light, visible aberrations are virtually absent until a threshold of approximately 80 ergs mm⁻¹ is reached. Aberrations then occur as a nonlinear function of dose. Chromatid aberrations are by far the most prevalent until doses in excess of 200 ergs mm⁻¹ are administered, at which point chromosome aberrations become common.


Metaphase Configurations In Drosophila: A Comparison Of Endemic Hawaiian Species And Non-Endemic Species, Frances E. Clayton Jan 1976

Metaphase Configurations In Drosophila: A Comparison Of Endemic Hawaiian Species And Non-Endemic Species, Frances E. Clayton

Journal of the Arkansas Academy of Science

The metaphase configurations of 400 strains from 63 species of Hawaiian Drosophila were determined from squash preparations of larval brain tissue or spermatogenic cells from adult testes. These karyotypes include configurations from seven species not previously described. Metaphases of 148 Hawaiian species have been recorded, including species of the "picture-wing" group, the "modified mouthpart" group, and the "bristle-foot" group. A comparison between Hawaiian species and non-endemic species was made on the basis of chromosome numbers and configurations. Among the Hawaiian species, 85.8% have retained the primitive haploid configuration of five rods and one dot compared with only 34.8% of species …


Electrophoretic Patterns Of Serum Proteins In Two Subspecies Of Odocoileus Virginianus, Greg S. Jackman, Phyllis J. Garnett Jan 1976

Electrophoretic Patterns Of Serum Proteins In Two Subspecies Of Odocoileus Virginianus, Greg S. Jackman, Phyllis J. Garnett

Journal of the Arkansas Academy of Science

Cellulose acetate electrophoresis revealed six monomorphic forms of serum protein in natural populations of two subspecies of white-tailed deer, Odocoileus virginianus virginianus from Tennessee and Odocoileus virginianus macroura from Arkansas. The fixed pattern of serum proteins in the two populations indicates a lack of genetic variation in the loci controlling these proteins. However, electrophoresis revealed different hemoglobin phenotypes in the two subspecies. This finding indicates that further study is needed to determine whether or not there are genetic differences in the hemoglobin forms


Somatic Pairing In Drosophila Virilis Mitosis, William C. Guest Jan 1975

Somatic Pairing In Drosophila Virilis Mitosis, William C. Guest

Journal of the Arkansas Academy of Science

In neuroblast cells homologous chromosomes tend to pair during prophase of mitosis. Heterochromatic elements of homologous chromosomes are widely separated in very early prophase, at which time the euchromatin is poorly stained. Pairing is intimate for euchromatic portions of chromosomes in early and middle prophase with chiasmata frequently present. Homologous chromosomes most commonly lie side-by-side in late prophase and metaphase. Statistical data are presented to show the frequency of intimate pairing in prophase and side by side pairing in metaphase.