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Pre-Columbian America
In the history of the Americas, the pre-Columbian era, also known as the pre-contact era, or as the pre-Cabraline era specifically in Brazil, spans from the initial peopling of the Americas in the Upper Paleolithic to the onset of European colonization, which began with Christopher Columbus's voyage in 1492. This era encompasses the history of Indigenous cultures prior to significant European influence, which in some cases did not occur until decades or even centuries after Columbus's arrival. During the pre-Columbian era, many civilizations developed permanent settlements, cities, agricultural practices, civic and monumental architecture, major earthworks, and complex societal hierarchies. Some of these civilizations had declined by the time of the establishment of the first permanent European colonies, around the late 16th to early 17th centuries, and are known primarily through archaeological research of the Americas and oral histories. Other civilizations, contemporan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Temple Of Kukulcán
El Castillo (, 'the Castle'), also known as the Temple of Kukulcan is a Mesoamerican pyramids, Mesoamerican step-pyramid that dominates the center of the Chichen Itza archaeological site in the Mexican state of Yucatán (state), Yucatán. The temple building is more formally designated by archaeologists as Chichen Itza Structure 5B18. Built by the pre-Columbian Maya civilization sometime between the 8th and 12th centuries AD, the building served as a temple to the deity Kukulcán, the Yucatec Maya Feathered Serpent (deity), Feathered Serpent deity closely related to Quetzalcoatl, a deity known to the Aztecs and other central Mexican cultures of the Postclassic period. It has a substructure that likely was constructed several centuries earlier for the same purpose. The temple consists of a series of square terraces with stairways up each of the four sides to the temple on top. Sculptures of plumed serpents run down the sides of the northern balustrade. Around the spring equinox (N ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
John Lloyd Stephens
John Lloyd Stephens (November 28, 1805October 13, 1852) was an American explorer, writer, and diplomat. He was a pivotal figure in the rediscovery of Maya civilization throughout Middle America (Americas), Middle America and in the planning of the Panama railway, Panama railroad. Early life John Lloyd Stephens was born November 28, 1805, in the township of Shrewsbury, New Jersey. He was the second son of Benjamin Stephens, a successful New Jersey merchant, and Clemence Lloyd, daughter of an eminent local judge. The following year the family moved to New York City. There Stephens received an education in the Classics at two privately tutored schools. At the age of 13, he enrolled at Columbia College of Columbia University, Columbia College, graduating at the top of his class four years later in 1822. After studying law with an attorney for a year, he attended the Litchfield Law School. He passed the bar exam after completing his course of study and practiced in New York City. St ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Mutations
In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, mitosis, or meiosis or other types of damage to DNA (such as pyrimidine dimers caused by exposure to ultraviolet radiation), which then may undergo error-prone repair (especially microhomology-mediated end joining), cause an error during other forms of repair, or cause an error during replication ( translesion synthesis). Mutations may also result from substitution, insertion or deletion of segments of DNA due to mobile genetic elements. Mutations may or may not produce detectable changes in the observable characteristics (phenotype) of an organism. Mutations play a part in both normal and abnormal biological processes including: evolution, cancer, and the development of the immune system, including junctional diversity. Mutation is the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Meiosis
Meiosis () is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, the sperm or egg cells. It involves two rounds of division that ultimately result in four cells, each with only one copy of each chromosome (haploid). Additionally, prior to the division, genetic material from the paternal and maternal copies of each chromosome is crossed over, creating new combinations of code on each chromosome. Later on, during fertilisation, the haploid cells produced by meiosis from a male and a female will fuse to create a zygote, a cell with two copies of each chromosome. Errors in meiosis resulting in aneuploidy (an abnormal number of chromosomes) are the leading known cause of miscarriage and the most frequent genetic cause of developmental disabilities. In meiosis, DNA replication is followed by two rounds of cell division to produce four daughter cells, each with half the number of chromosomes as the original parent cell. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Chromosome
A chromosome is a package of DNA containing part or all of the genetic material of an organism. In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells, the most important of these proteins are the histones. Aided by chaperone proteins, the histones bind to and condense the DNA molecule to maintain its integrity. These eukaryotic chromosomes display a complex three-dimensional structure that has a significant role in transcriptional regulation. Normally, chromosomes are visible under a light microscope only during the metaphase of cell division, where all chromosomes are aligned in the center of the cell in their condensed form. Before this stage occurs, each chromosome is duplicated ( S phase), and the two copies are joined by a centromere—resulting in either an X-shaped structure if the centromere is located equatorially, or a two-armed structure if the centromere is located distally; the jo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Mitochondrial DNA
Mitochondrial DNA (mtDNA and mDNA) is the DNA located in the mitochondrion, mitochondria organelles in a eukaryotic cell that converts chemical energy from food into adenosine triphosphate (ATP). Mitochondrial DNA is a small portion of the DNA contained in a eukaryotic cell; most of the DNA is in the cell nucleus, and, in plants and algae, the DNA also is found in plastids, such as chloroplasts. Mitochondrial DNA is responsible for coding of 13 essential subunits of the complex oxidative phosphorylation (OXPHOS) system which has a role in cellular energy conversion. Human mitochondrial DNA was the first significant part of the human genome to be sequenced. This sequencing revealed that human mtDNA has 16,569 base pairs and encodes 13 proteins. As in other vertebrates, the human mitochondrial genetic code differs slightly from nuclear DNA. Since animal mtDNA evolves faster than nuclear genetic markers, it represents a mainstay of phylogenetics and evolutionary biology. It als ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Y-chromosome DNA
In human genetics, a human Y-chromosome DNA haplogroup is a haplogroup defined by specific mutations in the non- recombining portions of DNA on the male-specific Y chromosome (Y-DNA). Individuals within a haplogroup share similar numbers of short tandem repeats (STRs) and single-nucleotide polymorphisms (SNPs). The Y-chromosome accumulates approximately two mutations per generation, "one mutation in every 30 million base pairs" and Y-DNA haplogroups represent significant branches of the Y-chromosome phylogenetic tree, each characterized by hundreds or even thousands of unique mutations. The Y-chromosomal most recent common ancestor (Y-MRCA), often referred to as Y-chromosomal Adam, is the most recent common ancestor from whom all currently living humans are descended patrilineally. Y-chromosomal Adam is estimated to have lived around 236,000 years ago in Africa. By examining other population bottlenecks, most Eurasian men trace their descent from a man who lived in Af ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Haplogroup Q1a3a (Y-DNA)
Haplogroup Q-M3 (Y-DNA) is a Y-chromosome DNA haplogroup. Haplogroup Q-M3 is a subclade of Haplogroup Q-L54. Haplogroup Q-M3 was previously known as Haplogroup Q3; currently Q-M3 is Q1b1a1a below Q1b-M346. In 1996 the research group at Stanford University headed by Dr. Peter Underhill first discovered the SNP that was to become known as M3. At the time, it was called DYS191. Later studies completed the genetic bridge by determining that Q-M3 was related to Q-M242-bearing populations who traveled through Central Asia to East Asia. Origin and distribution Haplogroup Q-M3 is one of the Y-Chromosome haplogroups linked to the indigenous peoples of the Americas (over 90% of indigenous people in Meso & South America). Today, such lineages also include other Q-M242 branches ( Q-M346, Q-L54, Q-P89.1, Q-NWT01, and Q-Z780), haplogroup C-M130 branches ( C-M217 and C-P39), and R-M207, which are almost exclusively found in North America. Haplogroup Q-M3 is defined by the presence of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
