part_of genome
An information ___MASK65___ ( IS ) is any organized ___MASK65___ for the collection , organization , storage and communication of information . More specifically , it is the study of complementary networks that people and organizations use to collect , filter , process , create and distribute data . A ___MASK68___ is an electrically neutral group of two or more atoms held together by chemical bonds . Molecules are distinguished from ions by their lack of electrical charge . However , in quantum physics , organic chemistry , and biochemistry , the term " ___MASK68___ " is often used less strictly , also being applied to polyatomic ions . ___MASK83___ is a natural science concerned with the study of life and living organisms , including their structure , function , growth , ___MASK2___ , distribution , identification and taxonomy . Modern biology is a vast and eclectic field , composed of many branches and subdisciplines . However , despite the broad scope of biology , there are certain general and unifying concepts within it that govern all study and research , consolidating it into single , coherent field . In general , biology recognizes the cell as the basic unit of life , genes as the basic unit of heredity , and ___MASK2___ as the engine that propels the synthesis and creation of new ___MASK82___ . It is also understood today that all the organisms survive by consuming and transforming energy and by regulating their internal environment to maintain a stable and vital condition known as homeostasis . Ribonucleic acid ( ___MASK10___ ) is a polymeric ___MASK68___ essential in various biological roles in coding , decoding , regulation , and expression of genes . ___MASK10___ and DNA are nucleic acids , and , along with proteins and carbohydrates , constitute the four major macromolecules essential for all known forms of life . Like DNA , ___MASK10___ is assembled as a chain of nucleotides , but unlike DNA it is more often found in nature as a single - strand folded onto itself , rather than a paired double - strand . Cellular organisms use messenger ___MASK10___ ( mRNA ) to convey genetic information ( using the letters G , U , A , and C to denote the nitrogenous bases guanine , uracil , adenine , and cytosine ) that directs synthesis of specific proteins . Many viruses encode their genetic information using an ___MASK10___ genome . ___MASK34___ is the study of genes , genetic variation , and heredity in living organisms . It is generally considered a field of biology , but intersects frequently with many other life sciences and is strongly linked with the study of information systems . William Thomas Astbury FRS ( also Bill Astbury ; ___MASK4___ February 1898 , Longton  4 ___MASK42___ 1961 , Leeds ) was an English physicist and molecular biologist who made pioneering X - ray diffraction studies of biological molecules . His work on keratin provided the foundation for Linus Pauling ' s discovery of the alpha helix . He also studied the structure for DNA in 1937 and made the first step in the elucidation of its structure . Messenger ___MASK10___ ( mRNA ) is a large family of ___MASK10___ molecules that convey genetic information from DNA to the ribosome , where they specify the amino acid sequence of the protein products of ___MASK47___ expression . Following transcription of primary transcript mRNA ( known as pre - mRNA ) by ___MASK10___ polymerase , processed , mature mRNA is translated into a polymer of amino acids : a protein , as summarized in the central dogma of molecular biology . A ___MASK65___ is a set of interacting or interdependent component parts forming a complex or intricate whole . Every ___MASK65___ is delineated by its spatial and temporal boundaries , surrounded and influenced by its environment , described by its structure and purpose and expressed in its functioning . A ___MASK47___ is a locus ( or region ) of DNA which is made up of nucleotides and is the molecular unit of heredity . The transmission of genes to an ___MASK14___ ' s offspring is the basis of the inheritance of phenotypic traits . Most biological traits are under the influence of polygenes ( many different genes ) as well as ___MASK47___  environment interactions . Some genetic traits are instantly visible , such as eye colour or number of limbs , and some are not , such as blood type , risk for specific diseases , or the thousands of basic biochemical processes that comprise life . ___MASK67___ is a characteristic distinguishing physical entities having biological processes , such as signaling and self - sustaining processes , from those that do not , either because such functions have ceased , or because they never had such functions and are classified as inanimate . Various forms of ___MASK67___ exist , such as plants , ___MASK44___ , fungi , protists , archaea , and bacteria . The criteria can at times be ambiguous and ___MASK29___ or ___MASK29___ not define viruses , viroids , or potential artificial ___MASK67___ as " living ". Biology is the primary science concerned with the study of ___MASK67___ , although many other sciences are involved . An ion is an ___MASK17___ or a ___MASK68___ in which the total number of electrons is not equal to the total number of protons , giving the ___MASK17___ or ___MASK68___ a net positive or negative electrical charge . Ions can be created , by either chemical or physical means , via ionization . A unicellular ___MASK14___ , also known as a single - celled ___MASK14___ , is an ___MASK14___ that consists of only one cell , unlike a multicellular ___MASK14___ that consists of more than one cell . Historically , simple unicellular organisms have been referred to as monads , though this term is also used more specifically to describe organisms of the genus " Monas " and similar flagellate ameboids . The main groups of unicellular organisms are bacteria , archaea , protozoa , unicellular algae , and unicellular fungi . Unicellular organisms fall into two general categories : prokaryotic organisms and eukaryotic organisms . Unicellular organisms are thought to be the oldest form of life , with early protocells possibly emerging 3 . 8  4 billion years ago . A carbohydrate is a biological ___MASK68___ consisting of carbon ( C ), hydrogen ( H ) and oxygen ( O ) atoms , usually with a hydrogen  oxygen atom ratio of 2 : 1 ( as in water ); in other words , with the empirical formula ( where " m " could be different from " n "). Some exceptions exist ; for example , deoxyribose , a sugar component of DNA , has the empirical formula CHO . Carbohydrates are technically hydrates of carbon ; structurally it is more accurate to view them as polyhydroxy aldehydes and ketones . A biomolecule or biological ___MASK68___ is ___MASK68___ that is present in living organisms , including large macromolecules such as proteins , carbohydrates , lipids , and nucleic acids , as well as small molecules such as primary metabolites , secondary metabolites , and natural products . A more general name for this class of material is biological materials . Biomolecules are usually endogenous but ___MASK29___ also be exogenous . For example , pharmaceutical drugs ___MASK29___ be natural products or semisynthetic ( biopharmaceuticals ) or they ___MASK29___ be totally synthetic . Multicellular organisms are organisms that consist of more than one ___MASK6___ , in contrast to unicellular organisms . Cytosine ( ___MASK20___ ) is one of the four main bases found in DNA and RNA , along with adenine , guanine , and thymine ( uracil in RNA ). It is a pyrimidine derivative , with a heterocyclic aromatic ring and two substituents attached ( an amine group at position 4 and a keto group at position 2 ). The nucleoside of cytosine is cytidine . In Watson - Crick base pairing , it forms three hydrogen bonds with guanine . In modern ___MASK25___ and ___MASK34___ , the genome is the genetic material of an ___MASK14___ . It consists of DNA ( or RNA in RNA viruses ) . The genome includes both the genes and the non - coding sequences of the DNA / RNA . A fungus ( plural : fungi or funguses ) is any member of the group of eukaryotic organisms that includes unicellular microorganisms such as yeasts and molds , as well as multicellular fungi that produce familiar fruiting forms such as mushrooms and bracket fungi . These organisms are classified as a kingdom , Fungi , which is separate from the other eukaryotic ___MASK67___ kingdoms of plants and ___MASK44___ . Nucleotides are organic molecules that serve as the monomers , or subunits , of nucleic acids like ___MASK89___ ( deoxyribonucleic acid ) and ___MASK10___ ( ribonucleic acid ). The building blocks of nucleic acids , nucleotides are composed of a nitrogenous base , a five - carbon sugar ( ribose or deoxyribose ), and at least one phosphate group . A nucleoside is a nitrogenuous base and a 5 - carbon sugar . Thus a nucleoside plus a phosphate group yields a nucleotide . Nucleotides are also known as phosphate nucleotides . Biopolymers are polymers produced by living organisms ; in other words , they are polymeric biomolecules . Since they are polymers , biopolymers contain monomeric units that are covalently bonded to form larger structures . There are three main classes of biopolymers , classified according to the monomeric units used and the structure of the biopolymer formed : polynucleotides ( ___MASK10___ and DNA ), which are long polymers composed of 13 or more nucleotide monomers ; polypeptides , which are short polymers of amino acids ; and polysaccharides , which are often linear bonded polymeric carbohydrate structures . Cellulose is the most common organic compound and biopolymer on ___MASK35___ . About 33 percent of all plant matter is cellulose . The cellulose content of cotton is 90 percent , for wood is 50 percent . The microscopic scale ( from , " mikrós ", " small " and  , " skopé " " look ") is the scale of objects and events smaller than those that can easily be seen by the naked ___MASK18___ , requiring a lens or microscope to see them clearly . In physics , the microscopic scale is sometimes considered the scale between the macroscopic and the quantum regime . ___MASK47___  environment interaction ( or ___MASK94___  environment interaction or G × E ) is when two different genotypes respond to environmental variation in different ways . A norm of reaction is a graph that shows the relationship between genes and environmental factors when phenotypic differences are continuous . They can help illustrate GxE interactions . When the norm of reaction is not parallel , as shown in the figure below , there is a gene by environment interaction . This indicates that each ___MASK94___ responds to environmental variation in a different way . Proteins ( or ) are large biomolecules , or macromolecules , consisting of one or more long chains of amino acid residues . Proteins perform a vast array of functions within organisms , including catalysing metabolic reactions , ___MASK89___ replication , responding to stimuli , and transporting molecules from one location to another . Proteins differ from one another primarily in their sequence of amino acids , which is dictated by the nucleotide sequence of their genes , and which usually results in protein folding into a specific three - dimensional structure that determines its activity . Homeostasis or homoeostasis is the property of a ___MASK65___ in which a variable ( for example , the concentration of a substance in solution , or its temperature ) is actively regulated to remain very nearly constant . This regulation occurs inside a defined environment ( mostly within a living ___MASK14___ ' s body ). Examples of homeostasis include the regulation of the body temperature of an animal , the pH of its extracellular fluids , or the concentrations of sodium ( Na ) and calcium ( Ca ) ions or of glucose in the blood plasma , despite changes in the animal  s environment , or what it has eaten , or what it is doing ( for example , resting or exercising ). Each of these variables is controlled by a separate  homeostat  ( or regulator ), which , together , maintain life . Homeostats are energy - consuming physiological mechanisms . Reproduction ( or procreation or breeding ) is the biological ___MASK76___ by which new individual organisms  " offspring "  are produced from their " parents ". Reproduction is a fundamental feature of all known ___MASK67___ ; each individual ___MASK14___ exists as the result of reproduction . There are two forms of reproduction : asexual and sexual . Adenine ( A , Ade ) is a nucleobase ( a purine derivative ). Its derivatives have a ___MASK24___ of roles in biochemistry including cellular respiration , in the form of both the energy - rich adenosine triphosphate ( ATP ) and the cofactors nicotinamide adenine dinucleotide ( NAD ) and flavin adenine dinucleotide ( FAD ). It also has functions in protein synthesis and as a chemical component of DNA and RNA . The shape of adenine is complementary to either thymine in DNA or uracil in RNA . Guanine ( or G , Gua ) is one of the four main nucleobases found in the nucleic acids ___MASK89___ and ___MASK10___ , the others being adenine , cytosine , and thymine ( uracil in ___MASK10___ ). In ___MASK89___ , guanine is paired with cytosine . The guanine nucleoside is called guanosine . Genetic variation means that biological systems  individuals and populations  are different over space . Each ___MASK47___ pool includes various alleles of genes . The variation occurs both within and among populations , supported by individual carriers of the variant genes . Nucleic acids are biopolymers , or large biomolecules , essential to all known forms of ___MASK67___ . They are composed of monomers , which are nucleotides made of three components : a 5 - carbon ___MASK57___ , a phosphate group , and a nitrogenous base . If the ___MASK57___ is a simple ribose , the polymer is ___MASK10___ ( ribonucleic acid ); if the ___MASK57___ is derived from ribose as deoxyribose , the polymer is DNA ( deoxyribonucleic acid ). ___MASK44___ are multicellular , eukaryotic organisms of the kingdom Animalia ( also called Metazoa ). The animal kingdom emerged as a basal clade within Apoikozoa as a sister of the choanoflagellates . Sponges are the most basal clade of ___MASK44___ . ___MASK44___ are motile , meaning they can move spontaneously and independently at some point in their lives . Their body plan eventually becomes fixed as they develop , although some undergo a process of metamorphosis later in their lives . All ___MASK44___ are heterotrophs : they must ingest other organisms or their products for sustenance . A macromolecule is a very large ___MASK68___ , such as protein , commonly created by polymerization of smaller subunits ( monomers ). They are typically composed of thousands of atoms or more . The most common macromolecules in biochemistry are biopolymers ( nucleic acids , proteins , carbohydrates and polyphenols ) and large non - polymeric molecules ( such as lipids and macrocycles ). Synthetic macromolecules include common plastics and synthetic fibres as well as experimental materials such as carbon nanotubes . A virus is a small infectious agent that replicates only inside the living cells of other organisms . Viruses can infect all types of ___MASK67___ forms , from ___MASK44___ and plants to microorganisms , including bacteria and archaea . Uracil ( U ) is one of the four nucleobases in the nucleic acid of ___MASK10___ that are represented by the letters A , G , ___MASK20___ and U . The others are adenine ( A ), cytosine ( ___MASK20___ ), and guanine ( G ). In ___MASK10___ , uracil binds to adenine via two hydrogen bonds . In DNA , the uracil nucleobase is replaced by thymine . Uracil is a demethylated form of thymine . ___MASK25___ concerns the molecular basis of biological activity between biomolecules in the various systems of a cell , including the interactions between DNA , ___MASK10___ , and proteins and their biosynthesis , as well as the regulation of these interactions . Writing in " Nature " in 1961 , William Astbury described molecular biology as : A polymer ( Greek " poly -", " many " + "- mer ", " parts ") is a large ___MASK68___ , or macromolecule , composed of many repeated subunits . Because of their broad range of properties , both synthetic and natural polymers play an essential and ubiquitous role in everyday life . Polymers range from familiar synthetic plastics such as polystyrene to natural biopolymers such as DNA and proteins that are fundamental to biological structure and function . Polymers , both natural and synthetic , are created via polymerization of many small molecules , known as monomers . Their consequently large molecular mass relative to small ___MASK68___ compounds produces unique physical properties , including toughness , viscoelasticity , and a tendency to form glasses and semicrystalline structures rather than crystals . In ___MASK83___ , an ___MASK14___ is any contiguous living system , such as an animal , plant , fungus , archaeon , or bacterium . All known types of organisms are capable of some degree of response to stimuli , reproduction , growth and development and homeostasis . An ___MASK14___ consists of one or more cells ; when it has one cell it is known as a unicellular ___MASK14___ ; and when it has more than one it is known as a multicellular ___MASK14___ . Most unicellular organisms are of microscopic scale and are thus loosely described as microorganisms . Humans are multicellular organisms composed of many trillions of cells grouped into specialized tissues and organs . Deoxyribonucleic acid ( ___MASK89___ ) is a ___MASK68___ that carries the genetic instructions used in the growth , development , functioning and reproduction of all known living organisms and many viruses . ___MASK89___ and RNA are nucleic acids ; alongside proteins , lipids and complex carbohydrates ( polysaccharides ), they are one of the four major types of macromolecules that are essential for all known forms of life . Most ___MASK89___ molecules consist of two biopolymer strands coiled around each other to form a double helix . Heredity is the genetic information passing for traits from parents to their offspring , either through asexual reproduction or ___MASK73___ . This is the process by which an offspring cell or ___MASK14___ acquires or becomes predisposed to the characteristics of its parent cell or ___MASK14___ . Through heredity , variations exhibited by individuals can accumulate and cause some ___MASK82___ to evolve through the natural selection of specific phenotype traits . The study of heredity in biology is called genetics , which includes the field of epigenetics .