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Subtelomeric Regions
Subtelomeres are segments of DNA between telomeric caps and chromatin. Structure Telomeres are specialized protein–DNA constructs present at the ends of eukaryotic chromosomes, which prevent them from degradation and end-to-end chromosome, chromosomal fusion. Most vertebrate telomeric DNA consists of long (Thymine, TThymine, TAdenine, AGuanine, GGuanine, GGuanine, G)n repeats of variable length, often around 3-20kb. ''Subtelomeres'' are segments of DNA between telomeric caps and chromatin. In vertebrates, each chromosome has two subtelomeres immediately adjacent to the long (TTAGGG)n repeats. Subtelomeres are considered to be the most distal (farthest from the centromere) region of unique DNA on a chromosome, and they are unusually dynamic and variable mosaics of multichromosomal blocks of sequence. The subtelomeres of such diverse species as humans, ''Plasmodium falciparum'', ''Drosophila melanogaster'', and ''Saccharomyces cerevisiae'' are structurally similar in that they ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telomere
A telomere (; ) is a region of repetitive nucleotide sequences associated with specialized proteins at the ends of linear chromosomes. Although there are different architectures, telomeres, in a broad sense, are a widespread genetic feature most commonly found in eukaryotes. In most, if not all species possessing them, they protect the terminal regions of chromosomal DNA from progressive degradation and ensure the integrity of linear chromosomes by preventing DNA repair systems from mistaking the very ends of the DNA strand for a double-strand break. Discovery In the early 1970s, Soviet theorist Alexei Olovnikov first recognized that chromosomes could not completely replicate their ends; this is known as the "end replication problem". Building on this, and accommodating Leonard Hayflick's idea of limited somatic cell division, Olovnikov suggested that DNA sequences are lost every time a cell replicates until the loss reaches a critical level, at which point cell division end ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deletion (genetics)
In genetics, a deletion (also called gene deletion, deficiency, or deletion mutation) (sign: Δ) is a mutation (a genetic aberration) in which a part of a chromosome or a sequence of DNA is left out during DNA replication. Any number of nucleotides can be deleted, from a single base to an entire piece of chromosome. Some chromosomes have fragile spots where breaks occur which result in the deletion of a part of chromosome. The breaks can be induced by heat, viruses, radiations, chemicals. When a chromosome breaks, a part of it is deleted or lost, the missing piece of chromosome is referred to as deletion or a deficiency. For synapsis to occur between a chromosome with a large intercalary deficiency and a normal complete homolog, the unpaired region of the normal homolog must loop out of the linear structure into a deletion or compensation loop. The smallest single base deletion mutations occur by a single base flipping in the template DNA, followed by template DNA strand sli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Pore
A nuclear pore is a part of a large complex of proteins, known as a nuclear pore complex that spans the nuclear envelope, which is the double membrane surrounding the eukaryotic cell nucleus. There are approximately 1,000 nuclear pore complexes (NPCs) in the nuclear envelope of a vertebrate cell, but this number varies depending on cell type and the stage in the life cycle. The human nuclear pore complex (hNPC) is a 110 megadalton (MDa) structure. The proteins that make up the nuclear pore complex are known as nucleoporins; each NPC contains at least 456 individual protein molecules and is composed of 34 distinct nucleoporin proteins. About half of the nucleoporins typically contain solenoid protein domains—either an alpha solenoid or a beta-propeller fold, or in some cases both as separate structural domains. The other half show structural characteristics typical of "natively unfolded" or intrinsically disordered proteins, i.e. they are highly flexible proteins that lack ord ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antigen
In immunology, an antigen (Ag) is a molecule or molecular structure or any foreign particulate matter or a pollen grain that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response. The term ''antigen'' originally referred to a substance that is an antibody generator. Antigens can be proteins, peptides (amino acid chains), polysaccharides (chains of monosaccharides/simple sugars), lipids, or nucleic acids. Antigens are recognized by antigen receptors, including antibodies and T-cell receptors. Diverse antigen receptors are made by cells of the immune system so that each cell has a specificity for a single antigen. Upon exposure to an antigen, only the lymphocytes that recognize that antigen are activated and expanded, a process known as clonal selection. In most cases, an antibody can only react to and bind one specific antigen; in some instances, however, antibodies may cross-react and bind more than one antigen. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trypanosoma Brucei
''Trypanosoma brucei'' is a species of parasitic Kinetoplastida, kinetoplastid belonging to the genus ''Trypanosoma'' that is present in sub-Saharan Africa. Unlike other protozoan parasites that normally infect blood and tissue cells, it is exclusively extracellular and inhabits the blood plasma and body fluids. It causes deadly vector-borne diseases: African trypanosomiasis or sleeping sickness in humans, and animal trypanosomiasis or ''nagana'' in cattle and horses. It is a species complex grouped into three subspecies: ''T. b. brucei'', ''T. b. gambiense'' and ''T. b. rhodesiense''. The first is a parasite of non-human mammals and causes ''nagana'', while the latter two are zoonotic infecting both humans and animals and cause African trpanosomiasis. ''T. brucei'' is transmitted between mammal hosts by an insect Vector (epidemiology), vector belonging to different species of tsetse fly (''Glossina''). Transmission occurs by biting during the insect's blood meal. The parasites un ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plasmodium
''Plasmodium'' is a genus of unicellular eukaryotes that are obligate parasites of vertebrates and insects. The life cycles of ''Plasmodium'' species involve development in a blood-feeding insect host which then injects parasites into a vertebrate host during a blood meal. Parasites grow within a vertebrate body tissue (often the liver) before entering the bloodstream to infect red blood cells. The ensuing destruction of host red blood cells can result in malaria. During this infection, some parasites are picked up by a blood-feeding insect (mosquitoes in majority cases), continuing the life cycle. ''Plasmodium'' is a member of the phylum Apicomplexa, a large group of parasitic eukaryotes. Within Apicomplexa, ''Plasmodium'' is in the order Haemosporida and family Plasmodiidae. Over 200 species of ''Plasmodium'' have been described, many of which have been subdivided into 14 subgenera based on parasite morphology and host range. Evolutionary relationships among different ''Pl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zinc-finger Protein
A zinc finger is a small protein structural motif that is characterized by the coordination of one or more zinc ions (Zn2+) in order to stabilize the fold. It was originally coined to describe the finger-like appearance of a hypothesized structure from the African clawed frog (''Xenopus laevis'') transcription factor IIIA. However, it has been found to encompass a wide variety of differing protein structures in eukaryotic cells. ''Xenopus laevis'' TFIIIA was originally demonstrated to contain zinc and require the metal for function in 1983, the first such reported zinc requirement for a gene regulatory protein followed soon thereafter by the Krüppel factor in ''Drosophila''. It often appears as a metal-binding domain in multi-domain proteins. Proteins that contain zinc fingers (zinc finger proteins) are classified into several different structural families. Unlike many other clearly defined supersecondary structures such as Greek keys or β hairpins, there are a number of typ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Immunoglobulin Heavy Chain
The immunoglobulin heavy chain (IgH) is the large polypeptide subunit of an antibody (immunoglobulin). In human genome, the IgH gene loci are on chromosome 14. A typical antibody is composed of two immunoglobulin (Ig) heavy chains and two Ig light chains. Several different types of heavy chain exist that define the class or isotype of an antibody. These heavy chain types vary between different animals. All heavy chains contain a series of immunoglobulin domains, usually with one variable domain (VH) that is important for binding antigen and several constant domains (CH1, CH2, etc.). Production of a viable heavy chain is a key step in B cell maturation. If the heavy chain is able to bind to a surrogate light chain and move to the plasma membrane, then the developing B cell can begin producing its light chain. The heavy chain doesn't always have to bind to a light chain. Pre-B lymphocytes can synthesize heavy chain in the absence of light chain, which then can allow the heavy ch ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Olfactory Receptor
Olfactory receptors (ORs), also known as odorant receptors, are chemoreceptors expressed in the cell membranes of olfactory receptor neurons and are responsible for the detection of odorants (for example, compounds that have an odor) which give rise to the sense of smell. Activated olfactory receptors trigger nerve impulses which transmit information about odor to the brain. These receptors are members of the class A rhodopsin-like family of G protein-coupled receptors (GPCRs). The olfactory receptors form a multigene family consisting of around 800 genes in humans and 1400 genes in mice. Expression In vertebrates, the olfactory receptors are located in both the cilia and synapses of the olfactory sensory neurons and in the epithelium of the human airway. In insects, olfactory receptors are located on the antennae and other chemosensory organs. Sperm cells also express odor receptors, which are thought to be involved in chemotaxis to find the egg cell. Mechanism Rat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene Families
A gene family is a set of several similar genes, formed by duplication of a single original gene, and generally with similar biochemical functions. One such family are the genes for human hemoglobin subunits; the ten genes are in two clusters on different chromosomes, called the α-globin and β-globin loci. These two gene clusters are thought to have arisen as a result of a precursor gene being duplicated approximately 500 million years ago. Genes are categorized into families based on shared nucleotide or protein sequences. Phylogenetic techniques can be used as a more rigorous test. The positions of exons within the coding sequence can be used to infer common ancestry. Knowing the sequence of the protein encoded by a gene can allow researchers to apply methods that find similarities among protein sequences that provide more information than similarities or differences among DNA sequences. If the genes of a gene family encode proteins, the term '' protein family'' is often ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pseudogene
Pseudogenes are nonfunctional segments of DNA that resemble functional genes. Most arise as superfluous copies of functional genes, either directly by DNA duplication or indirectly by Reverse transcriptase, reverse transcription of an mRNA transcript. Pseudogenes are usually identified when genome sequence analysis finds gene-like sequences that lack regulatory sequences needed for Transcription (biology), transcription or Translation (biology), translation, or whose coding sequences are obviously defective due to Frameshift mutation, frameshifts or premature stop codons. Most non-bacterial genomes contain many pseudogenes, often as many as functional genes. This is not surprising, since various biological processes are expected to accidentally create pseudogenes, and there are no specialized mechanisms to remove them from genomes. Eventually pseudogenes may be deleted from their genomes by chance DNA replication or DNA repair errors, or they may accumulate so many mutational cha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Haplotype
A haplotype ( haploid genotype) is a group of alleles in an organism that are inherited together from a single parent. Many organisms contain genetic material ( DNA) which is inherited from two parents. Normally these organisms have their DNA organized in two sets of pairwise similar chromosomes. The offspring gets one chromosome in each pair from each parent. A set of pairs of chromosomes is called diploid and a set of only one half of each pair is called haploid. The haploid genotype (haplotype) is a genotype that considers the singular chromosomes rather than the pairs of chromosomes. It can be all the chromosomes from one of the parents or a minor part of a chromosome, for example a sequence of 9000 base pairs. However, there are other uses of this term. First, it is used to mean a collection of specific alleles (that is, specific DNA sequences) in a cluster of tightly linked genes on a chromosome that are likely to be inherited together—that is, they are likely to be con ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
