scholarly journals Positive and Purifying Selection on the Drosophila Y Chromosome

2014 ◽  
Vol 31 (10) ◽  
pp. 2612-2623 ◽  
Author(s):  
Nadia D. Singh ◽  
Leonardo B. Koerich ◽  
Antonio Bernardo Carvalho ◽  
Andrew G. Clark
Keyword(s):  
Y Chromosome ◽  
Purifying Selection

scholarly journals Inefficient purifying selection: the mammalian Y chromosome in the rodent genus Mus

2006 ◽  
Vol 17 (1) ◽  
pp. 14-21
Author(s):  
Sara A. Sandstedt ◽  
Priscilla K. Tucker
Keyword(s):  
Y Chromosome ◽  
Purifying Selection

scholarly journals Plant Y Chromosome Degeneration Is Retarded by Haploid Purifying Selection

2011 ◽  
Vol 21 (17) ◽  
pp. 1475-1479 ◽  
Author(s):  
Margarita V. Chibalina ◽  
Dmitry A. Filatov
Keyword(s):  
Y Chromosome ◽  
Purifying Selection ◽  
Y Chromosome Degeneration

scholarly journals Why Chromosome Palindromes?

2012 ◽  
Vol 2012 ◽  
pp. 1-14 ◽  
Author(s):  
Esther Betrán ◽  
Jeffery P. Demuth ◽  
Anna Williford
Keyword(s):  
Gene Conversion ◽  
Y Chromosome ◽  
Adaptive Evolution ◽  
Purifying Selection ◽  
Duplicate Gene ◽  
Adaptive Significance ◽  
Deleterious Mutations ◽  
Initial Fixation ◽  
Selection For ◽  
Y Degeneration

We look at sex-limited chromosome (Y or W) evolution with particular emphasis on the importance of palindromes. Y chromosome palindromes consist of inverted duplicates that allow for local recombination in an otherwise nonrecombining chromosome. Since palindromes enable intrachromosomal gene conversion that can help eliminate deleterious mutations, they are often highlighted as mechanisms to protect against Y degeneration. However, the adaptive significance of recombination resides in its ability to decouple the evolutionary fates of linked mutations, leading to both a decrease in degeneration rate and an increase in adaptation rate. Our paper emphasizes the latter, that palindromes may exist to accelerate adaptation by increasing the potential targets and fixation rates of incoming beneficial mutations. This hypothesis helps reconcile two enigmatic features of the “palindromes as protectors” view: (1) genes that are not located in palindromes have been retained under purifying selection for tens of millions of years, and (2) under models that only consider deleterious mutations, gene conversion benefits duplicate gene maintenance but not initial fixation. We conclude by looking at ways to test the hypothesis that palindromes enhance the rate of adaptive evolution of Y-linked genes and whether this effect can be extended to palindromes on other chromosomes.

scholarly journals High rate of translocation-based gene birth on the Drosophila Y chromosome

2017 ◽  
Vol 114 (44) ◽  
pp. 11721-11726 ◽  
Author(s):  
Ray Tobler ◽  
Viola Nolte ◽  
Christian Schlötterer
Keyword(s):  
Y Chromosome ◽  
Molecular Mechanisms ◽  
Evolutionary Dynamics ◽  
Purifying Selection ◽  
High Rate ◽  
Linked Gene ◽  
The Past ◽  
New Genes ◽  
Gene Acquisition ◽  
Next Generation Sequencing Ngs

The Y chromosome is a unique genetic environment defined by a lack of recombination and male-limited inheritance. The Drosophila Y chromosome has been gradually acquiring genes from the rest of the genome, with only seven Y-linked genes being gained over the past 63 million years (0.12 gene gains per million years). Using a next-generation sequencing (NGS)-powered genomic scan, we show that gene transfers to the Y chromosome are much more common than previously suspected: at least 25 have arisen across three Drosophila species over the past 5.4 million years (1.67 per million years for each lineage). The gene transfer rate is significantly lower in Drosophila melanogaster than in the Drosophila simulans clade, primarily due to Y-linked retrotranspositions being significantly more common in the latter. Despite all Y-linked gene transfers being evolutionarily recent (<1 million years old), only three showed evidence for purifying selection (ω ≤ 0.14). Thus, although the resulting Y-linked functional gene acquisition rate (0.25 new genes per million years) is double the longer-term estimate, the fate of most new Y-linked genes is defined by rapid degeneration and pseudogenization. Our results show that Y-linked gene traffic, and the molecular mechanisms governing these transfers, can diverge rapidly between species, revealing the Drosophila Y chromosome to be more dynamic than previously appreciated. Our analytical method provides a powerful means to identify Y-linked gene transfers and will help illuminate the evolutionary dynamics of the Y chromosome in Drosophila and other species.

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.

Detection Y Chromosome Microdeletions Among Iraq Population in Infertile Patients with Azoospermia and Severe Oligospermia

2019 ◽  
Vol 9 (02) ◽  
Author(s):  
Samah A Hammood ◽  
Alaauldeen S M AL-Sallami ◽  
Saleh M Al-Khafaji
Keyword(s):  
Y Chromosome ◽  
Karyotype Analysis ◽  
Semen Analysis ◽  
Obstructive Azoospermia ◽  
Severe Oligozoospermia ◽  
Infertile Men ◽  
Y Chromosome Microdeletions ◽  
Detailed Evaluation ◽  
Health Organization ◽  
Infertile Patients

Objective: To detection of microdeletions of Y chromosome and study the frequency of microdeletions in infertile men with non-obstructive azoospermia or severe oligozoospermia(Middle Euphrates center)in Iraq population. Material and methods: 153 males were included in the study, the casesweredivided into groups according to the infertility etiology and semen analysis according to Word health organization, the frequencies and the characteristicsof Y chromosome microdeletions were investigated in groups. Multiplex PCR was applied to detect the microdeletions. Results:Y chromosome microdeletion was detected in 42 (40.7%) of 153 cases ,Microdeletions in azoospermia showed more frequently detected 28 (52.8%), followed by severe oligospermia 14 (28 %),Microdeletions in the AZFc region were the most common 12 (22.64%), followed by AZFb 11(20.75%) and AZFa 5(9.43%) in azoospermia compared to severe oligospermisAZFc 6 (12%) AZFb 4 (8 %) and AZFa 4 (8%). Conclusion: Y chromosome microdeletions were detected quite frequently in certain infertility subgroups. Therefore, detailed evaluation of an infertile man by physical examination, semen analysis, hormonal evaluationsand when required, karyotype analysis may predict the patients for whom Y chromosome microdeletionanalysis is necessary and also prevent cost increases. Recommendation: This study emphasizes that analysis of microdeletions should be carried out for all patients with idiopathic azoospermia and severe oligospermia who are candidates for intracytoplasmic sperm injection

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