Sampling Nucleotide Diversity in Cotton

Abstract Comparison of the levels of nucleotide diversity in humans and apes may provide much insight into the mechanisms of maintenance of DNA polymorphism and the demographic history of these organisms. In the past, abundant mitochondrial DNA (mtDNA) polymorphism data indicated that nucleotide diversity (π) is more than threefold higher in chimpanzees than in humans. Furthermore, it has recently been claimed, on the basis of limited data, that this is also true for nuclear DNA. In this study we sequenced 50 noncoding, nonrepetitive DNA segments randomly chosen from the nuclear genome in 9 bonobos and 17 chimpanzees. Surprisingly, the π value for bonobos is only 0.078%, even somewhat lower than that (0.088%) for humans for the same 50 segments. The π values are 0.092, 0.130, and 0.082% for East, Central, and West African chimpanzees, respectively, and 0.132% for all chimpanzees. These values are similar to or at most only 1.5 times higher than that for humans. The much larger difference in mtDNA diversity than in nuclear DNA diversity between humans and chimpanzees is puzzling. We speculate that it is due mainly to a reduction in effective population size (Ne) in the human lineage after the human-chimpanzee divergence, because a reduction in Ne has a stronger effect on mtDNA diversity than on nuclear DNA diversity.

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Sequence Variation and Haplotype Structure at the HumanHFELocus

Genetics ◽

10.1093/genetics/161.4.1609 ◽

2002 ◽

Vol 161 (4) ◽

pp. 1609-1623 ◽

Cited By ~ 4

Author(s):

Christopher Toomajian ◽

Martin Kreitman

Keyword(s):

High Frequency ◽

Nucleotide Diversity ◽

Sequence Variation ◽

Hla Class I ◽

Selective Advantage ◽

European Ancestry ◽

Iron Regulation ◽

Intragenic Recombination ◽

Nucleotide Variability ◽

Show Evidence

AbstractThe HFE locus encodes an HLA class-I-type protein important in iron regulation and segregates replacement mutations that give rise to the most common form of genetic hemochromatosis. The high frequency of one disease-associated mutation, C282Y, and the nature of this disease have led some to suggest a selective advantage for this mutation. To investigate the context in which this mutation arose and gain a better understanding of HFE genetic variation, we surveyed nucleotide variability in 11.2 kb encompassing the HFE locus and experimentally determined haplotypes. We fully resequenced 60 chromosomes of African, Asian, or European ancestry as well as one chimpanzee, revealing 41 variable sites and a nucleotide diversity of 0.08%. This indicates that linkage to the HLA region has not substantially increased the level of HFE variation. Although several haplotypes are shared between populations, one haplotype predominates in Asia but is nearly absent elsewhere, causing higher than average genetic differentiation among the three major populations. Our samples show evidence of intragenic recombination, so the scarcity of recombination events within the C282Y allele class is consistent with selection increasing the frequency of a young allele. Otherwise, the pattern of variability in this region does not clearly indicate the action of positive selection at this or linked loci.

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Insights into phylogenetic relationships and genome evolution of subfamily Commelinoideae (Commelinaceae Mirb.) inferred from complete chloroplast genomes

BMC Genomics ◽

10.1186/s12864-021-07541-1 ◽

2021 ◽

Vol 22 (1) ◽

Author(s):

Joonhyung Jung ◽

Changkyun Kim ◽

Joo-Hwan Kim

Keyword(s):

Nucleotide Diversity ◽

Structural Variations ◽

Protein Coding ◽

Protein Coding Genes ◽

Chloroplast Protein ◽

Genome Data ◽

Plastid Genomes ◽

Chloroplast Genomes ◽

Current Classification

Abstract Background Commelinaceae (Commelinales) comprise 41 genera and are widely distributed in both the Old and New Worlds, except in Europe. The relationships among genera in this family have been suggested in several morphological and molecular studies. However, it is difficult to explain their relationships due to high morphological variations and low support values. Currently, many researchers have been using complete chloroplast genome data for inferring the evolution of land plants. In this study, we completed 15 new plastid genome sequences of subfamily Commelinoideae using the Mi-seq platform. We utilized genome data to reveal the structural variations and reconstruct the problematic positions of genera for the first time. Results All examined species of Commelinoideae have three pseudogenes (accD, rpoA, and ycf15), and the former two might be a synapomorphy within Commelinales. Only four species in tribe Commelineae presented IR expansion, which affected duplication of the rpl22 gene. We identified inversions that range from approximately 3 to 15 kb in four taxa (Amischotolype, Belosynapsis, Murdannia, and Streptolirion). The phylogenetic analysis using 77 chloroplast protein-coding genes with maximum parsimony, maximum likelihood, and Bayesian inference suggests that Palisota is most closely related to tribe Commelineae, supported by high support values. This result differs significantly from the current classification of Commelinaceae. Also, we resolved the unclear position of Streptoliriinae and the monophyly of Dichorisandrinae. Among the ten CDS (ndhH, rpoC2, ndhA, rps3, ndhG, ndhD, ccsA, ndhF, matK, and ycf1), which have high nucleotide diversity values (Pi > 0.045) and over 500 bp length, four CDS (ndhH, rpoC2, matK, and ycf1) show that they are congruent with the topology derived from 77 chloroplast protein-coding genes. Conclusions In this study, we provide detailed information on the 15 complete plastid genomes of Commelinoideae taxa. We identified characteristic pseudogenes and nucleotide diversity, which can be used to infer the family evolutionary history. Also, further research is needed to revise the position of Palisota in the current classification of Commelinaceae.

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High Polymorphism at the Human Melanocortin 1 Receptor Locus

Genetics ◽

10.1093/genetics/151.4.1547 ◽

1999 ◽

Vol 151 (4) ◽

pp. 1547-1557 ◽

Cited By ~ 4

Author(s):

Brinda K Rana ◽

David Hewett-Emmett ◽

Li Jin ◽

Benny H-J Chang ◽

Naymkhishing Sambuughin ◽

...

Keyword(s):

Protein Sequence ◽

Nucleotide Diversity ◽

Coat Color ◽

Low Frequency ◽

Melanocortin Receptor ◽

Human Populations ◽

Melanocortin 1 Receptor ◽

Mc1r Gene ◽

Southeast Asians ◽

Color Changes

Abstract Variation in human skin/hair pigmentation is due to varied amounts of eumelanin (brown/black melanins) and phaeomelanin (red/yellow melanins) produced by the melanocytes. The melanocortin 1 receptor (MC1R) is a regulator of eu- and phaeomelanin production in the melanocytes, and MC1R mutations causing coat color changes are known in many mammals. We have sequenced the MC1R gene in 121 individuals sampled from world populations with an emphasis on Asian populations. We found variation at five nonsynonymous sites (resulting in the variants Arg67Gln, Asp84Glu, Val92Met, Arg151Cys, and Arg163Gln), but at only one synonymous site (A942G). Interestingly, the human consensus protein sequence is observed in all 25 African individuals studied, but at lower frequencies in the other populations examined, especially in East and Southeast Asians. The Arg163Gln variant is absent in the Africans studied, almost absent in Europeans, and at a low frequency (7%) in Indians, but is at an exceptionally high frequency (70%) in East and Southeast Asians. The MC1R gene in common and pygmy chimpanzees, gorilla, orangutan, and baboon was sequenced to study the evolution of MC1R. The ancestral human MC1R sequence is identical to the human consensus protein sequence, while MC1R varies considerably among higher primates. A comparison of the rates of substitution in genes in the melanocortin receptor family indicates that MC1R has evolved the fastest. In addition, the nucleotide diversity at the MC1R locus is shown to be several times higher than the average nucleotide diversity in human populations, possibly due to diversifying selection.

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Plasmodium vivax Cysteine-Rich Protective Antigen Polymorphism at Exon-1 Shows Recombination and Signatures of Balancing Selection

Genes ◽

10.3390/genes12010029 ◽

2020 ◽

Vol 12 (1) ◽

pp. 29

Author(s):

Lilia González-Cerón ◽

José Cebrián-Carmona ◽

Concepción M. Mesa-Valle ◽

Federico García-Maroto ◽

Frida Santillán-Valenzuela ◽

...

Keyword(s):

Amino Acid ◽

B Cell ◽

Plasmodium Vivax ◽

Nucleotide Diversity ◽

Protective Antigen ◽

Balancing Selection ◽

Southern Mexico ◽

Exon 2 ◽

Exon 1 ◽

Tajima’S D

Plasmodium vivax Cysteine-Rich Protective Antigen (CyRPA) is a merozoite protein participating in the parasite invasion of human reticulocytes. During natural P. vivax infection, antibody responses against PvCyRPA have been detected. In children, low anti-CyRPA antibody titers correlated with clinical protection, which suggests this protein as a potential vaccine candidate. This work analyzed the genetic and amino acid diversity of pvcyrpa in Mexican and global parasites. Consensus coding sequences of pvcyrpa were obtained from seven isolates. Other sequences were extracted from a repository. Maximum likelihood phylogenetic trees, genetic diversity parameters, linkage disequilibrium (LD), and neutrality tests were analyzed, and the potential amino acid polymorphism participation in B-cell epitopes was investigated. In 22 sequences from Southern Mexico, two synonymous and 21 nonsynonymous mutations defined nine private haplotypes. These parasites had the highest LD-R2 index and the lowest nucleotide diversity compared to isolates from South America or Asia. The nucleotide diversity and Tajima’s D values varied across the coding gene. The exon-1 sequence had greater diversity and Rm values than those of exon-2. Exon-1 had significant positive values for Tajima’s D, β-α values, and for the Z (HA: dN > dS) and MK tests. These patterns were similar for parasites of different origin. The polymorphic amino acid residues at PvCyRPA resembled the conformational B-cell peptides reported in PfCyRPA. Diversity at pvcyrpa exon-1 is caused by mutation and recombination. This seems to be maintained by balancing selection, likely due to selective immune pressure, all of which merit further study.

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Patterns of DNA Variability at X-Linked Loci in Mus domesticus

Genetics ◽

10.1093/genetics/147.3.1303 ◽

1997 ◽

Vol 147 (3) ◽

pp. 1303-1316

Author(s):

Michael W Nachman

Keyword(s):

Drosophila Melanogaster ◽

X Chromosome ◽

House Mouse ◽

Recombination Rate ◽

Nucleotide Diversity ◽

Mus Domesticus ◽

Substantial Variation ◽

Intraspecific Polymorphism ◽

Recombination Rates ◽

Interspecific Divergence

Introns of four X-linked genes (Hprt, Plp, Glra2, and Amg) were sequenced to provide an estimate of nucleotide diversity at nuclear genes within the house mouse and to test the neutral prediction that the ratio of intraspecific polymorphism to interspecific divergence is the same for different loci. Hprt and Plp lie in a region of the X chromosome that experiences relatively low recombination rates, while Glra2 and Amg lie near the telomere of the X chromosome, a region that experiences higher recombination rates. A total of 6022 bases were sequenced in each of 10 Mus domesticus and one M. caroli. Average nucleotide diversity (π) for introns within M. domesticus was quite low (π = 0.078%). However, there was substantial variation in the level of heterozygosity among loci. The two telomeric loci, Glra2 and Amg, had higher ratios of polymorphism to divergence than the two loci experiencing lower recombination rates. These results are consistent with the hypothesis that heterozygosity is reduced in regions with lower rates of recombination, although sampling of additional genes is needed to establish whether there is a general correlation between heterozygosity and recombination rate as in Drosophila melanogaster.

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Hierarchical Analysis of Nucleotide Diversity in Geographically Structured Populations

Genetics ◽

10.1093/genetics/142.2.629 ◽

1996 ◽

Vol 142 (2) ◽

pp. 629-639 ◽

Cited By ~ 4

Author(s):

Kent E Holsinger ◽

Roberta J Mason-Gamer

Keyword(s):

Nucleotide Diversity ◽

Restriction Site ◽

Rooted Tree ◽

Structured Populations ◽

Hierarchical Analysis ◽

Restriction Site Variation ◽

Hierarchical Levels ◽

Site Variation ◽

The Mean ◽

Mean Time

Abstract Existing methods for analyzing nucleotide diversity require investigators to identify relevant hierarchical levels before beginning the analysis. We describe a method that partitions diversity into hierarchical components while allowing any structure present in the data to emerge naturally. We present an unbiased version of Nei's nucleotide diversity statistics and show that our modification has the same properties as Wright's F ST. We compare its statistical properties with several other F ST estimators, and we describe how to use these statistics to produce a rooted tree of relationships among the sampled populations in which the mean time to coalescence of haplotypes drawn from populations belonging to the same node is smaller than the mean time to coalescence of haplotypes drawn from populations belonging to different nodes. We illustrate the method by applying it to data from a recent survey of restriction site variation in the chloroplast genome of Coreopsis grandiflora.

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