Related Experiment Video
Updated: Dec 21, 2025
08:46
Preparation of Meiotic Chromosome Spreads from Zebrafish Spermatocytes
Published on: March 3, 2020
8.4K
Guppy Y Chromosome Integrity Maintained by Incomplete Recombination Suppression
Iulia Darolti1, Alison E Wright2, Judith E Mank1,3
1Biodiversity Research Centre and Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada.
Genome Biology and Evolution
|May 20, 2020
Summary
In livebearers like Poecilia reticulata and Poecilia wingei, incomplete recombination suppression between sex chromosomes maintains their similarity. This ongoing recombination hinders rapid sex chromosome divergence and degeneration.
Area of Science:
- Evolutionary genetics
- Comparative genomics
- Sex chromosome evolution
Background:
- Sex chromosome systems evolve through recombination suppression, leading to divergence and degeneration.
- The genus Poecilia exhibits a 20-million-year-old male-heterogametic system with varying Y chromosome divergence.
- Poecilia reticulata and Poecilia wingei show low X-Y divergence despite recombination restriction, offering a model for studying divergence forces.
Purpose of the Study:
- To investigate the evolutionary forces shaping sex chromosome divergence in Poecilia reticulata and Poecilia wingei.
- To understand the role of recombination suppression in maintaining sex chromosome homomorphy.
- To analyze the historical patterns of recombination arrest and its relationship with sex-determining loci.
Main Methods:
- RNA sequencing (RNA-seq) data from multiple families of P. reticulata and P. wingei.
- Differentiation of X and Y coding sequences using sex-limited single nucleotide polymorphism (SNP) inheritance.
- Phylogenetic tree analyses of X-Y orthologs.
Main Results:
- Phylogenetic analyses indicate persistent, albeit occasional, recombination across much of the Poecilia sex chromosomes.
- X- and Y-linked sequences cluster by species, not by gametolog, due to ongoing recombination.
- Incomplete recombination suppression maintains sex chromosome homomorphy in these species.
- Older strata, associated with the sex-determining locus, show distinct phylogenetic clustering of X-Y orthologs compared to younger strata.
- Recombination arrest appears to have expanded gradually, not via discrete inversion-driven steps.
Conclusions:
- Incomplete recombination suppression is a key factor maintaining sex chromosome similarity in Poecilia reticulata and Poecilia wingei.
- The gradual expansion of recombination arrest, rather than stepwise inversions, characterizes the evolution of these sex chromosomes.
- Understanding these mechanisms provides insights into the diverse evolutionary trajectories of sex chromosomes across species.
Related Concept Videos
03:17Inheritance of Chromatin Structures
7.2K
Epigenetics is the study of inherited changes in a cell's phenotype without changing the DNA sequences. It provides a form of memory for the differential gene expression pattern to maintain cell lineage, position-effect variegation, dosage compensation, and maintenance of chromatin structures such as telomeres and centromeres. For example, the structure and location of the centromere on chromosomes are epigenetically inherited. Its functionality is not dictated or ensured by the underlying...
7.2K
02:08Gene Conversion
10.5K
Other than maintaining genome stability via DNA repair, homologous recombination plays an important role in diversifying the genome. In fact, the recombination of sequences forms the molecular basis of genomic evolution. Random and non-random permutations of genomic sequences create a library of new amalgamated sequences. These newly formed genomes can determine the fitness and survival of cells. In bacteria, homologous and non-homologous types of recombination lead to the evolution of new...
10.5K
02:53Conservative Site-specific Recombination and Phase Variation
6.5K
Because the DNA segments are cut and reorganized in a direction-specific manner, site-specific recombination has emerged as an efficient genetic engineering technique. Flippase and Cyclization recombinases or Flp and Cre, respectively, are two members of the tyrosine recombinase family derived from bacteriophages, that are used to mediate site-specific DNA insertions, deletions, and targeted expression of proteins in mammalian cell lines.
The recognition sites for Cre recombinase called LoxP...
The recognition sites for Cre recombinase called LoxP...
6.5K
01:58X-Inactivation
41.1K
The human X chromosome contains over ten times the number of genes as in the Y chromosome. Since males have only one X chromosome, and females have two, one might expect females to produce twice as many of the proteins, with undesirable results.
41.1K
02:32X and Y Chromosomes
29.1K
Among mammals, the gender of an organism is determined by the sex chromosomes. Humans have two sex chromosomes, X and Y. Every human diploid cell has 22 pairs of autosomes and one pair of sex chromosomes. A human female has two X chromosomes, while a male has one X chromosome and one Y chromosome.
The germline cells such as egg and sperm cells carry only half the number of chromosomes, i.e., 22 autosomes and one sex chromosome. All eggs have an X chromosome, while sperm cells can carry an X or...
The germline cells such as egg and sperm cells carry only half the number of chromosomes, i.e., 22 autosomes and one sex chromosome. All eggs have an X chromosome, while sperm cells can carry an X or...
29.1K
01:30Crossing Over
5.9K
Crossing over is the exchange of genetic information between homologous chromosomes during prophase I of meiosis I. Genetic recombination gives rise to allelic diversity in the newly formed daughter cells. In humans, crossing over produces genetically distinct haploid egg and sperm cells that undergo fertilization to produce unique offspring. Before cell division starts, the germ cell’s chromosome(s) undergo duplication in the S phase of the cell cycle. As the cells enter prophase I,...
5.9K