Can You Identify the Structures of a Chromosome?
chromosome, the microscopic threadlike part of the jail cell that carries hereditary information in the course of genes. A defining feature of any chromosome is its compactness. For instance, the 46 chromosomes constitute in man cells have a combined length of 200 nm (1 nm = 10− 9 metre); if the chromosomes were to be unraveled, the genetic material they contain would measure roughly two metres (about half-dozen.5 feet) in length. The compactness of chromosomes plays an of import role in helping to organize genetic material during cell segmentation and enabling it to fit within structures such as the nucleus of a cell, the average diameter of which is about 5 to x μm (ane μm = 0.00l mm, or 0.000039 inch), or the polygonal caput of a virus particle, which may exist in the range of just xx to 30 nm in diameter.
The construction and location of chromosomes are among the principal differences between viruses, prokaryotes, and eukaryotes. The nonliving viruses have chromosomes consisting of either Dna (deoxyribonucleic acid) or RNA (ribonucleic acid); this material is very tightly packed into the viral head. Among organisms with prokaryotic cells (i.e., bacteria and blueish-green algae), chromosomes consist entirely of DNA. The unmarried chromosome of a prokaryotic prison cell is not enclosed inside a nuclear membrane. Amongst eukaryotes, the chromosomes are independent in a membrane-bound cell nucleus. The chromosomes of a eukaryotic prison cell consist primarily of Dna attached to a protein core. They also incorporate RNA. The balance of this commodity pertains to eukaryotic chromosomes.
Deoxyribonucleic acid wraps around proteins called histones to class units known every bit nucleosomes. These units condense into a chromatin fibre, which condenses further to form a chromosome.
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Every eukaryotic species has a characteristic number of chromosomes (chromosome number). In species that reproduce asexually, the chromosome number is the same in all the cells of the organism. Among sexually reproducing organisms, the number of chromosomes in the body (somatic) cells is diploid (2n; a pair of each chromosome), twice the haploid (onen) number establish in the sex cells, or gametes. The haploid number is produced during meiosis. During fertilization, 2 gametes combine to produce a zygote, a single cell with a diploid set of chromosomes. See also polyploidy.
Somatic cells reproduce by dividing, a process called mitosis. Between jail cell divisions the chromosomes exist in an uncoiled state, producing a lengthened mass of genetic material known as chromatin. The uncoiling of chromosomes enables Dna synthesis to brainstorm. During this phase, Deoxyribonucleic acid duplicates itself in grooming for prison cell division.
Following replication, the Dna condenses into chromosomes. At this point, each chromosome actually consists of a set of duplicate chromatids that are held together by the centromere. The centromere is the point of attachment of the kinetochore, a protein structure that is connected to the spindle fibres (part of a structure that pulls the chromatids to reverse ends of the jail cell). During the middle phase in jail cell division, the centromere duplicates, and the chromatid pair separates; each chromatid becomes a separate chromosome at this point. The cell divides, and both of the daughter cells accept a consummate (diploid) prepare of chromosomes. The chromosomes uncoil in the new cells, once again forming the diffuse network of chromatin.
Among many organisms that take separate sexes, in that location are two basic types of chromosomes: sex chromosomes and autosomes. Autosomes control the inheritance of all the characteristics except the sex activity-linked ones, which are controlled by the sex chromosomes. Humans have 22 pairs of autosomes and i pair of sex activity chromosomes. All human action in the same mode during cell division. For information on sex-linked characteristics, see linkage group.
Chromosome breakage is the physical breakage of subunits of a chromosome. Information technology is usually followed by reunion (frequently at a strange site, resulting in a chromosome unlike the original). Breakage and reunion of homologous chromosomes during meiosis are the basis for the classical model of crossing over, which results in unexpected types of offspring of a mating.
This article was most recently revised and updated by Adam Augustyn.
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Source: https://www.britannica.com/science/chromosome
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