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Population analysis of an unusual NOR-site polymorphism in brown trout (Salmo trutta L.)

Population analysis of an unusual NOR-site polymorphism in brown trout (Salmo trutta L.)
Population analysis of an unusual NOR-site polymorphism in brown trout (Salmo trutta L.)
A population analysis of an unusual NOR-site polymorphism previouslydetected in brown trout (Salmo trutta L.) from North-western Spain wascarried out in 225 individuals from 20 native populations from this area. Theanalysis performed has permitted us to reveal: (i) the ubiquity of thisphenomenon in most river basins from NW Spain, 13 extra-NORs not observed instandard trout being detected; (ii) the rDNA constitution of all extra-NORs, asconfirmed by CMA3-staining and rDNA-FISH, and their capability to constitutetheir own nucleolus; (iii) the constant location of extra-NORs withinindividuals and their stable transmission across generations; and (iv) thetelomeric location of Ag-NORs, which were randomly distributed in the karyotypeof S. trutta, mostly in the heterozygous condition. Repetitivesequences in the IGS or scattered along rDNA units, rather than chromosomerearrangements, could play an important role in the dispersion of NORs. Thepolymorphism described seems to have a single geographical origin, since apositive correlation was demonstrated between the degree of polymorphism andgeographical distance to a central point of the river basin where thephenomenon showed a higher intensity. The distribution of NOR-site variation ascompared with allozyme variation in the populations studied, showed significantstatistical differences. Selection against high copy number, or mutation due tochanges in NOR location, could be acting on this polymorphism to explain theobserved distribution. The high dispersion of NOR-site variants within andamong populations suggests the transposition phenomenon responsible for NORjumping could be still active.
allozyme variation, gene diversity, NOR dispersion, NOR-site polymorphism, population analysis, Salmo trutta
0018-067X
291 - 302
Castro, J.
7b4efc25-3334-4c07-8255-41be390b919b
Rodriguez, S.
b047a823-28c8-4043-8d4f-dc6b23f52e4e
Pardo, B. G.
d3906b59-3e1f-45ed-9764-56382cbbc806
Sanchez, L.
a83e68dd-8360-461d-a1f6-2de5615ada18
Martinez, P.
e7b48137-e01d-47cb-851c-c40b4a980562
Castro, J.
7b4efc25-3334-4c07-8255-41be390b919b
Rodriguez, S.
b047a823-28c8-4043-8d4f-dc6b23f52e4e
Pardo, B. G.
d3906b59-3e1f-45ed-9764-56382cbbc806
Sanchez, L.
a83e68dd-8360-461d-a1f6-2de5615ada18
Martinez, P.
e7b48137-e01d-47cb-851c-c40b4a980562

Castro, J., Rodriguez, S., Pardo, B. G., Sanchez, L. and Martinez, P. (2001) Population analysis of an unusual NOR-site polymorphism in brown trout (Salmo trutta L.). Heredity, 86 (3), 291 - 302.

Record type: Article

Abstract

A population analysis of an unusual NOR-site polymorphism previouslydetected in brown trout (Salmo trutta L.) from North-western Spain wascarried out in 225 individuals from 20 native populations from this area. Theanalysis performed has permitted us to reveal: (i) the ubiquity of thisphenomenon in most river basins from NW Spain, 13 extra-NORs not observed instandard trout being detected; (ii) the rDNA constitution of all extra-NORs, asconfirmed by CMA3-staining and rDNA-FISH, and their capability to constitutetheir own nucleolus; (iii) the constant location of extra-NORs withinindividuals and their stable transmission across generations; and (iv) thetelomeric location of Ag-NORs, which were randomly distributed in the karyotypeof S. trutta, mostly in the heterozygous condition. Repetitivesequences in the IGS or scattered along rDNA units, rather than chromosomerearrangements, could play an important role in the dispersion of NORs. Thepolymorphism described seems to have a single geographical origin, since apositive correlation was demonstrated between the degree of polymorphism andgeographical distance to a central point of the river basin where thephenomenon showed a higher intensity. The distribution of NOR-site variation ascompared with allozyme variation in the populations studied, showed significantstatistical differences. Selection against high copy number, or mutation due tochanges in NOR location, could be acting on this polymorphism to explain theobserved distribution. The high dispersion of NOR-site variants within andamong populations suggests the transposition phenomenon responsible for NORjumping could be still active.

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More information

Published date: 2001
Keywords: allozyme variation, gene diversity, NOR dispersion, NOR-site polymorphism, population analysis, Salmo trutta

Identifiers

Local EPrints ID: 24647
URI: https://eprints.soton.ac.uk/id/eprint/24647
ISSN: 0018-067X
PURE UUID: 9480a9d7-f819-40e5-bdca-d0c36bbba2c3

Catalogue record

Date deposited: 06 Apr 2006
Last modified: 17 Jul 2017 16:13

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