Karyotype, nucleolus organiser regions and constitutive heterochromatin in Ostrea angasi (Molluscae: Bivalvia): evidence of taxonomic relationships within the Ostreidae

1997 ◽  
Vol 127 (3) ◽  
pp. 443-448 ◽  
Author(s):  
X. X. Li ◽  
J. N. Havenhand
Keyword(s):  
Constitutive Heterochromatin ◽  
Taxonomic Relationships ◽  
Nucleolus Organiser

The deer of the island of Lampedusa (Pelagian Archipelago, Italy): literary references and osteological evidence

2002 ◽  
Vol 29 (1) ◽  
pp. 51-66 ◽  
Author(s):  
MARCO MASSETP ◽  
BRUNO ZAVA
Keyword(s):  
Nineteenth Century ◽  
Cervus Elaphus ◽  
Red Deer ◽  
Scientific Literature ◽  
Taxonomic Relationships

During the nineteenth century, scientific literature and official reports recorded the occurrence of a population of red deer, Cervus elaphus, on the island of Lampedusa (Pelagian Archipelago, Italy). Osteological specimens collected by the zoologist Enrico Hillier Giglioli towards the end of the century confirmed these references. Since cervids are not found among the fossil fauna of the island, the red deer must have been introduced by man although we do not yet know precisely when. The former existence of the species on Lampedusa is discussed by comparison of literary material and bone evidence. The population's probable origins and its taxonomic relationships with other Mediterranean red deer populations are also analysed.

Sex determination and Y chromosome constitutive heterochromatin

2019 ◽  
Vol 1 (1) ◽  
pp. 1-5
Author(s):  
Abyt Ibraimov
Keyword(s):  
Sex Determination ◽  
Y Chromosome ◽  
Constitutive Heterochromatin ◽  
Sex Differentiation ◽  
Secondary Sexual Characteristics ◽  
Biological Meaning ◽  
Heterochromatin Block ◽  
Sexual Characteristics ◽  
Open Question ◽  
Efficient Elimination

In many animals, including us, the genetic sex is determined at fertilization by sex chromosomes. Seemingly, the sex determination (SD) in human and animals is determined by the amount of constitutive heterochromatin on Y chromosome via cell thermoregulation. It is assumed the medulla and cortex tissue cells in the undifferentiated embryonic gonads (UEG) differ in vulnerability to the increase of the intracellular temperature. If the amount of the Y chromosome constitutive heterochromatin is enough for efficient elimination of heat difference between the nucleus and cytoplasm in rapidly growing UEG cells the medulla tissue survives. Otherwise it doomed to degeneration and a cortex tissue will remain in the UEG. Regardless of whether our assumption is true or not, it remains an open question why on Y chromosome there is a large constitutive heterochromatin block? What is its biological meaning? Does it relate to sex determination, sex differentiation and development of secondary sexual characteristics? If so, what is its mechanism: chemical or physical? There is no scientifically sound answer to these questions.

Cytogenetic and Taxonomic Relationships among Three Diploid Crested Wheatgrasses 1

Crop Science ◽  
1982 ◽  
Vol 22 (3) ◽  
pp. 645-650 ◽  
Author(s):  
D. R. Dewey ◽  
K. H. Asay
Keyword(s):  
Taxonomic Relationships

Radial Growth Responses to Temperature by 58ChaetomiumSpecies, and Some Taxonomic Relationships

Mycologia ◽  
1977 ◽  
Vol 69 (3) ◽  
pp. 492-502 ◽  
Author(s):  
P. D. Millner
Keyword(s):  
Radial Growth ◽  
Growth Responses ◽  
Taxonomic Relationships

Structure and variability of nucleolar organizer regions in Parodontidae fish

1984 ◽  
Vol 26 (5) ◽  
pp. 564-568 ◽  
Author(s):  
Orlando Moreira-Filho ◽  
Luiz Antonio Carlos Bertollo ◽  
Pedro Manoel Galetti Jr.
Keyword(s):  
Chromosome Pair ◽  
Constitutive Heterochromatin ◽  
Nucleolar Organizer ◽  
Nucleolar Organizer Regions ◽  
Mitotic Chromosomes ◽  
Homozygous Condition ◽  
Nucleolar Organizing Regions ◽  
Nucleolar Chromosome

Nucleolar organizer regions (NORs) were studied in mitotic chromosomes of four species of fish of family Parodontidae: Parodon tortuosus, Apareiodon affinis, Apareiodon ibitiensis, and Apareiodon piracicabae. All four species exhibited only a single nucleolar chromosome pair in their karyotypes. Intraspecific differences were observed in the size of these chromosomes; however, these were not very clear for A. affinis and A. piracicabae, Apareiodon piracicabae exhibited two clearly visible NORs in each of the nucleolar chromosomes, which was the only configuration practically found in this species. This trait therefore predominates in a homozygous condition in the population investigated. Regions of constitutive heterochromatin adjacent to the two NORs were detected. Possible mechanisms that may have originated the two NORs are discussed.Key words: nucleolar organizing regions, fish.

Two new species of Amphinemura (Plecoptera: Nemouridae) from China

Zootaxa ◽  
2011 ◽  
Vol 2975 (1) ◽  
pp. 29 ◽  
Author(s):  
WEIHAI LI ◽  
DING YANG
Keyword(s):  
New Species ◽  
Related Species ◽  
Taxonomic Relationships ◽  
Two New Species

Two new species of the genus Amphinemura from Ningxia and Zhejiang, China are described: A. ningxiana sp. n. and A. tianmushana sp. n. Their taxonomic relationships with related species are discussed.

Constitutive heterochromatin in Microtus agrestis: binding of actinomycin-D and transcriptional inactivity

Chromosoma ◽  
1971 ◽  
Vol 35 (1) ◽  
pp. 84-98 ◽  
Author(s):  
M. Sieger ◽  
G. Garweg ◽  
H. G. Schwarzacher
Keyword(s):  
Actinomycin D ◽  
Constitutive Heterochromatin ◽  
Microtus Agrestis

CHROMOSOME STRUCTURE IN CHILOCORUS (COLEOPTERA: COCCINELLIDAE). II. THE ASYNCHRONOUS REPLICATION OF CONSTITUTIVE HETEROCHROMATIN

1976 ◽  
Vol 18 (1) ◽  
pp. 85-91 ◽  
Author(s):  
T. J. Ennis
Keyword(s):  
Chromosome Banding ◽  
Chromosome Structure ◽  
Constitutive Heterochromatin ◽  
Chromosome Replication ◽  
Data Models ◽  
Late Replication ◽  
Banding Patterns ◽  
Asynchronous Replication ◽  
Chilocorus Stigma

Chromosome replication has been analysed in four species of Chilocorus. In C. orbus Csy., C. tricyclus Smith, and C. hexacyclus Smith, centric regions of all chromosomes are last to replicate, preceded in order by heterochromatic arms and euchromatic arms. In C. stigma Say, very late replication of centric regions can be detected only in otherwise wholly euchromatic chromosomes (= monophasics); in chromosomes with one arm heterochromatic (= diphasics), these arms are last to replicate. Based on pachytene bivalent morphology and chromosome banding patterns, and supported by autoradiographic data, models are presented for the general organisation of Chilocorus chromosomes. All chromosomes in the first three species are subdivided into euchromatic arm, centric heterochromatin, and either a second euchromatic arm (monophasics) or a heterochromatic arm (diphasics). Chilocorus stigma diphasics apparently lack distinct centric organisation, and are therefore divided into euchromatic and heterochromatic arms only.

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