Chromatid - wikipedia Chromatid This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. ( April 2018 ) In the diagram, ( 1 ) refers to a chromatid : one - half of two identical threadlike strands of a replicated chromosome. During cell division, the identical copies ( called a `` sister chromatid pair '' ) are joined at the region called the centromere ( 2 ). Once the paired sister chromatids have separated from one another ( in the anaphase of DJ mitosis ) each is known as a daughter chromosome. The short arm of the right chromatid ( 3 ), and the long arm of the right chromatid ( 4 ), are also marked. A chromatid ( Greek khrōmat - ' color ' + - id ) is one copy of a newly copied chromosome which is still joined to the original chromosome by a single centromere. Before replication, one chromosome is composed of one DNA molecule. Following replication, each chromosome is composed of two DNA molecules ; in other words, DNA replication itself increases the amount of DNA but does not increase the number of chromosomes. The two identical copies -- each forming one half of the replicated chromosome -- are called chromatids. During the later stages of cell division these chromatids separate longitudinally to become individual chromosomes. Chromatid pairs are normally genetically identical, and said to be homozygous ; however, if mutation ( s ) occur, they will present slight differences, in which case they are heterozygous. The pairing of chromatids should not be confused with the ploidy of an organism, which is the number of homologous versions of a chromosome. Chromonema is the fibre - like structure in prophase in the primary stage of DNA condensation. In metaphase, they are called chromatids. Sister chromatids Main article : Sister chromatids Chromatids may be sister or non-sister chromatids. A sister chromatid is either one of the two chromatids of the same chromosome joined together by a common centromere. A pair of sister chromatids is called a dyad. Once sister chromatids have separated ( during the anaphase of mitosis or the anaphase II of meiosis during sexual reproduction ), they are again called chromosomes. Although having the same genetic mass as the individual chromatids that made up its parent, the daughter `` molecules '' are called chromosomes in a similar way that one child of a pair of twins is not referred to as a single twin. The DNA sequence of two sister chromatids is completely identical ( apart from very rare DNA copying errors ). Sister chromatid exchange ( SCE ) is the exchange of genetic information between two sister chromatids. SCEs can occur during mitosis or meiosis. SCEs appear to primarily reflect DNA recombinational repair processes responding to DNA damage ( see articles Sister chromatids and Sister chromatid exchange ). Non-sister chromatids, on the other hand, refers to either of the two chromatids of paired homologous chromosomes, that is, the pairing of a paternal chromosome and a maternal chromosome. In chromosomal crossovers, non-sister ( homologous ) chromatids form chiasmata to exchange genetic material during the prophase I of meiosis ( See Homologous recombination ). References Look up chromatid in Wiktionary, the free dictionary. Jump up ^ `` What is a Chromatid ? ''. About.com. Retrieved 18 July 2017. Jump up ^ `` Definition of CHROMATID ''. www.Merriam-Webster.com. Retrieved 18 July 2017. Cytogenetics : chromosomes Basic concepts Karyotype Ploidy Genetic material / Genome Chromatin Euchromatin Heterochromatin Chromosome Chromatid Nucleosome Nuclear organization Types Autosome / Sex chromosome ( or allosome or heterosome ) Macrochromosome / Microchromosome Circular chromosome / Linear chromosome Extra chromosome ( or accessory chromosome ) Supernumerary chromosome A chromosome / B chromosome Lampbrush chromosome Polytene chromosome Dinoflagellate chromosomes Homologous chromosome Isochromosome Satellite chromosome Centromere position Metacentric Submetacentric Telocentric Acrocentric Holocentric Centromere number Acentric Monocentric Dicentric Polycentric Processes and evolution Mitosis Meiosis Structural alterations Chromosomal inversion Chromosomal translocation Numerical alterations Aneuploidy Euploidy Polyploidy Paleopolyploidy Polyploidization Structures Telomere : Telomere - binding protein ( TINF2 ) Protamine Histone H1 H2A H2B H3 H4 Centromere C1 C2 Q See also Extrachromosomal DNA Plasmid List of organisms by chromosome count List of chromosome lengths for various organisms List of sequenced genomes International System for Human Cytogenetic Nomenclature Retrieved from `` https://en.wikipedia.org/w/index.php?title=Chromatid&oldid=833861936 '' Categories : Chromosomes Molecular genetics Cell biology Mitosis Telomeres Hidden categories : Articles needing additional references from April 2018 All articles needing additional references Talk About Wikipedia Afrikaans Català Čeština Dansk Deutsch Español Euskara فارسی Français Gaeilge Galego 한국어 Հայերեն Hrvatski Italiano עברית ქართული Қазақша Kurdî Кыргызча Nederlands 日本 語 Occitan Polski Português Русский Simple English Српски / srpski Srpskohrvatski / српскохрватски Svenska Türkçe 中文 24 more Edit links This page was last edited on 2 April 2018, at 19 : 29. 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Question: before prophase i chromatid arms in a chromosome are
Answer: chiasmata