What Can the Y Chromosome Tell Us about the Origin of Modern Humans?

2004 ◽  
Author(s):  
Chris Tyler-Smith
Keyword(s):  
Y Chromosome ◽  
Common Ancestor ◽  
Population Characteristics ◽  
Pseudoautosomal Region ◽  
Modern Humans ◽  
Homology Region ◽  
Genetic History ◽  
Trace Back ◽  
Origin Of Modern Humans

This chapter outlines the peculiar genetic history and population characteristics of the Y chromosome, including the interaction with the X. The small size of the Y and its sex-limited transmission make it at first sight an unlikely vehicle for the determining characteristic of the species. Human and ape Y lineages are generally believed to have split about 5–7 million years ago, while extant human Y lineages trace back to a common ancestor that probably lived between 40 and 200 thousand years ago. Between these dates, two substantial segments of DNA on the Y chromosome were duplicated on the Y: the Yq pseudoautosomal region and the Xq/Yp homology region. The former does not contain any good candidate speciation genes but the latter may. The Xq-Yp transposition probably occurred soon after the ape-human split and, at the same time or subsequently, was divided in two by an inversion.

scholarly journals Meiotic Behavior of Achiasmate Sex Chromosomes in the African Pygmy Mouse Mus mattheyi Offers New Insights into the Evolution of Sex Chromosome Pairing and Segregation in Mammals

Genes ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1434
Author(s):  
Ana Gil-Fernández ◽  
Marta Ribagorda ◽  
Marta Martín-Ruiz ◽  
Pablo López-Jiménez ◽  
Tamara Laguna ◽  
...  
Keyword(s):  
Dna Repair ◽  
Y Chromosome ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Mammalian Species ◽  
Evolutionary Process ◽  
Small Region ◽  
Pseudoautosomal Region ◽  
Evolution Of Sex ◽  
African Pygmy Mouse

X and Y chromosomes in mammals are different in size and gene content due to an evolutionary process of differentiation and degeneration of the Y chromosome. Nevertheless, these chromosomes usually share a small region of homology, the pseudoautosomal region (PAR), which allows them to perform a partial synapsis and undergo reciprocal recombination during meiosis, which ensures their segregation. However, in some mammalian species the PAR has been lost, which challenges the pairing and segregation of sex chromosomes in meiosis. The African pygmy mouse Mus mattheyi shows completely differentiated sex chromosomes, representing an uncommon evolutionary situation among mouse species. We have performed a detailed analysis of the location of proteins involved in synaptonemal complex assembly (SYCP3), recombination (RPA, RAD51 and MLH1) and sex chromosome inactivation (γH2AX) in this species. We found that neither synapsis nor chiasmata are found between sex chromosomes and their pairing is notably delayed compared to autosomes. Interestingly, the Y chromosome only incorporates RPA and RAD51 in a reduced fraction of spermatocytes, indicating a particular DNA repair dynamic on this chromosome. The analysis of segregation revealed that sex chromosomes are associated until metaphase-I just by a chromatin contact. Unexpectedly, both sex chromosomes remain labelled with γH2AX during first meiotic division. This chromatin contact is probably enough to maintain sex chromosome association up to anaphase-I and, therefore, could be relevant to ensure their reductional segregation. The results presented suggest that the regulation of both DNA repair and epigenetic modifications in the sex chromosomes can have a great impact on the divergence of sex chromosomes and their proper transmission, widening our understanding on the relationship between meiosis and the evolution of sex chromosomes in mammals.

scholarly journals A Middle Palaeolithic burial of a modern human at Taramsa Hill, Egypt

Antiquity ◽  
1998 ◽  
Vol 72 (277) ◽  
pp. 475-484 ◽  
Author(s):  
P. M. Vermeersch ◽  
E. Paulissen ◽  
P. Van Peer ◽  
S. Stokes ◽  
C. Charlier ◽  
...  
Keyword(s):  
East Africa ◽  
Late Pleistocene ◽  
Modern Human ◽  
Nile Valley ◽  
Middle Palaeolithic ◽  
African Origin ◽  
Modern Humans ◽  
Origin Of Modern Humans ◽  
Clear Relation ◽  
Aeolian Sands

Discussion about a possible African origin of modern humans is hampered by the lack of Late Pleistocene skeletal material from the Nile valley, the likely passage-way from East Africa to Asia and Europe. Here we report the discovery of a burial of an anatomically modern child from southern Egypt. Its clear relation with Middle Palaeolithic chert extraction activities and a series of OSL dates, from correlative aeolian sands, suggests an age between 49,800 and 80,400 years ago, with a mean age of 55,000.

Energetics and the Origin of Modern Humans

2013 ◽  
pp. 285-320 ◽  
Author(s):  
Andrew W. Froehle ◽  
Todd R. Yokley ◽  
Steven E. Churchill
Keyword(s):  
Modern Humans ◽  
Origin Of Modern Humans

scholarly journals Y-Chromosome Evidence for a Northward Migration of Modern Humans into Eastern Asia during the Last Ice Age

1999 ◽  
Vol 65 (6) ◽  
pp. 1718-1724 ◽  
Author(s):  
Bing Su ◽  
Junhua Xiao ◽  
Peter Underhill ◽  
Ranjan Deka ◽  
Weiling Zhang ◽  
...  
Keyword(s):  
Y Chromosome ◽  
Ice Age ◽  
Eastern Asia ◽  
Modern Humans ◽  
Last Ice Age

Genetic Content of the Neo-Sex Chromosomes in Ctenonotus and Norops (Squamata, Dactyloidae) and Degeneration of the Y Chromosome as Revealed by High-Throughput Sequencing of Individual Chromosomes

2019 ◽  
Vol 157 (1-2) ◽  
pp. 115-122 ◽  
Author(s):  
Artem P. Lisachov ◽  
Alexey I. Makunin ◽  
Massimo Giovannotti ◽  
Jorge C. Pereira ◽  
Anna S. Druzhkova ◽  
...  
Keyword(s):  
Y Chromosome ◽  
X Chromosome ◽  
High Throughput ◽  
Sex Chromosomes ◽  
High Throughput Sequencing ◽  
Anolis Carolinensis ◽  
Pseudoautosomal Region ◽  
Central Component ◽  
Similar System ◽  
Divergence Estimates

Pleurodont lizards are characterized by an ancient system of sex chromosomes. Along with stability of the central component of the system (homologous to the X chromosome of Anolis carolinensis [Dactyloidae], ACAX), in some genera the ancestral sex chromosomes are fused with microautosomes, forming neo-sex chromosomes. The genus Ctenonotus (Dactyloidae) is characterized by multiple X1X1X2X2/X1X2Y sex chromosomes. According to cytogenetic data, the large neo-Y chromosome is formed by fusion of the ancestral Y chromosome with 2 microautosomes (homologous to ACA10 or ACA11 and ACA12), the X1 chromosome is formed by fusion of the ancestral X chromosome with the autosome homologous to ACA10 or ACA11, and the X2 chromosome is homologous to autosome ACA12. To determine more precisely the content and evolution of the Ctenonotus sex chromosomes, we sequenced flow-sorted chromosomes (both sex chromosomes and microautosomes as control) of 2 species with a similar system: C. pogus and C. sabanus. Our results indicate that the translocated part of the X1 is homologous to ACA11, X2 is homologous to ACA12, and the Y contains segments homologous to both ACA11 and ACA12. Molecular divergence estimates suggest that the ancestral X-derived part has completely degenerated in the Y of Ctenonotus, similar to the degeneration of the Norops sagrei Y chromosome (Dactyloidae). The newly added regions show loss of DNA content, but without degeneration of the conserved regions. We hypothesize that the translocation of autosomal blocks onto sex chromosomes facilitated rapid degeneration of the pseudoautosomal region on the ancestral Y.

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