Image of chicken chromosomes featuring the many microchromosomes (appearing as dots). The arrows indicate a stained gene locus on homologous macrochromosomes.
A microchromosome is a chromosome defined for its relatively small size. They are typical components of the karyotype of birds, some reptiles, fish, amphibians, and monotremes.[1] As many bird genomes have chromosomes of widely different lengths, the name was meant to distinguish them from the comparatively large macrochromosomes.[2] The distinction referred to the measured size of the chromosome while staining for karyotype, and while there is not a strict definition, chromosomes resembling the large chromosomes of mammals were called macrochromosomes (roughly 3 to 6 μm), while the much smaller ones of less than around 0.5 μm were called microchromosomes.[3] In terms of base pairs, by convention, those of less than 20Mb were called microchromosomes, those between 20 and 40 Mb are classified as intermediate chromosomes, and those larger than 40Mb are macrochromosomes.[4] By this definition, all normal chromosomes in organisms with relatively small genomes (less than 100-200Mb) would be considered microchromosomes.
^Hillier, LaDeana W.; International Chicken Genome Sequencing Consortium (December 2004). "Sequence and comparative analysis of the chicken genome provide unique perspectives on vertebrate evolution". Nature. 432 (7018): 695–716. Bibcode:2004Natur.432..695C. doi:10.1038/nature03154. PMID 15592404.
^Cite error: The named reference Waters21 was invoked but never defined (see the help page).
^Axelsson, Erik; Webster, Matthew T.; Smith, Nick G. C.; Burt, David W.; Ellegren, Hans (2005). "Comparison of the chicken and turkey genomes reveals a higher rate of nucleotide divergence on microchromosomes than macrochromosomes". Genome Research. 15 (1): 120–5. doi:10.1101/gr.3021305. PMC 540272. PMID 15590944.
A microchromosome is a chromosome defined for its relatively small size. They are typical components of the karyotype of birds, some reptiles, fish, amphibians...
of most turtles, Trionychids have ZZ/ZW genetic sex determination; microchromosomes play a role in determining sex. Softshell turtles are eaten as a delicacy...
Roscoe; Engstrom, Tag; Valenzuela, Nicole (2013-04-01). "A ZZ/ZW microchromosome system in the spiny softshell turtle, Apalone spinifera, reveals an...
A human artificial chromosome (HAC) is a microchromosome that can act as a new chromosome in a population of human cells. That is, instead of 46 chromosomes...
regulated by a common subset of genes. Their genome has a large number of microchromosomes which are lost during the animal's development, leaving only the reproductive...
is 2n=80, consisting of four pairs of macrochromosomes, 35 pairs of microchromosomes, and a pair of sex chromosomes. The two largest macrochromosome pairs...
Roscoe; Engstrom, Tag; Valenzuela, Nicole (2013-04-01). "A ZZ/ZW microchromosome system in the spiny softshell turtle, Apalone spinifera, reveals an...
Roscoe; Engstrom, Tag; Valenzuela, Nicole (2013-04-01). "A ZZ/ZW microchromosome system in the spiny softshell turtle, Apalone spinifera, reveals an...
has microchromosomes. It is also hypothesized that this turtle's sex chromosomes were formed from the translocation of an ancestral Y microchromosome onto...
2n=80, consisting of three pairs of macrochromosomes, 36 pairs of microchromosomes, and a pair of sex chromosomes. The two largest macrochromosome pairs...
Roscoe; Engstrom, Tag; Valenzuela, Nicole (2013-04-01). "A ZZ/ZW microchromosome system in the spiny softshell turtle, Apalone spinifera, reveals an...
most birds consist of a small number of macrochromosomes and numerous microchromosomes. Intriguingly, most accipitrids which include hawks, eagles, kites...
Roscoe; Engstrom, Tag; Valenzuela, Nicole (2013-03-20). "A ZZ/ZW microchromosome system in the spiny softshell turtle, Apalone spinifera, reveals an...
the in vivo micronucleus test. Macronucleus Cancerous micronuclei Microchromosome "Micronucleus". ntp.niehs.nih.gov. Archived from the original on 2016-10-18...
specifically populations in the Amazon region, is the presence of a B microchromosome, a particularly small type of chromosome present in some birds, reptiles...
Roscoe; Engstrom, Tag; Valenzuela, Nicole (2013-03-20). "A ZZ/ZW microchromosome system in the spiny softshell turtle, Apalone spinifera, reveals an...
effects than the monkeys. Induced genetic abnormality assays including microchromosome reverse mutation and E. coli mutagenicity assays were completed using...
constructed using the de novo approach. Minichromosome maintenance proteins Microchromosome Y chromosome, §Degeneration Xu, Chunhui; Yu, Weichang (2009). "Engineered...
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