THE ORIGIN OF SEX CHROMOSOMES IN HUMANS Miguel Ángel Rosales Motos Master in Advanced Genetics Genomics 11 th of December, 2019
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THE ORIGIN OF SEX
CHROMOSOMES IN
HUMANS
Miguel Ángel Rosales Motos
Master in Advanced Genetics
Genomics
11th of December, 2019
INDEX
1. Introduction
2. Origin of human sex chromosomes
3. Organization of human sex chromosomes
4. Conclusions
5. References
INTRODUCTIONSEX DETERMINATION
ENVIRONMENTAL SEX DETERMINATION GENETICALLY CONTROLLED SEX DETERMINATION
INTRODUCTIONSEX DETERMINATION
ENVIRONMENTAL SEX DETERMINATION GENETICALLY CONTROLLED SEX DETERMINATION
Sexual determination based on the
temperature
INTRODUCTIONSEX DETERMINATION
ENVIRONMENTAL SEX DETERMINATION
GENETICALLY CONTROLLED SEX DETERMINATION
XY/XX
Sexual determination based on the
temperature
INTRODUCTIONSEX DETERMINATION
ENVIRONMENTAL SEX DETERMINATION
GENETICALLY CONTROLLED SEX DETERMINATION
XY/XX ZW/ZZ
Sexual determination based on the
temperature
INTRODUCTIONSEX DETERMINATION
ENVIRONMENTAL SEX DETERMINATION
GENETICALLY CONTROLLED SEX DETERMINATION
XY/XX ZW/ZZ
X0/XX or Z0/ZZ
Sexual determination based on the
temperature
INTRODUCTIONSEX DETERMINATION
ENVIRONMENTAL SEX DETERMINATION
GENETICALLY CONTROLLED SEX DETERMINATION
XY/XX ZW/ZZ
X0/XX or Z0/ZZ Neo-sex chromosomes
Sexual determination based on the
temperature
INTRODUCTIONSEX DETERMINATION
ENVIRONMENTAL SEX DETERMINATION
GENETICALLY CONTROLLED SEX DETERMINATION
XY/XX ZW/ZZ
X0/XX or Z0/ZZ Neo-sex chromosomes
Ring / chain systemSexual determination based on the
temperature
INTRODUCTIONSEX DETERMINATION
Graves et al., 2015
Vertebrates sex
chromosomes and
phylogeny
SEX CHROMOSOMES IN HUMANS
➢ Testis-determining factor in
the proto-Y; beneficial
genes around it
➢ Recombination is
suppressed
➢ The two X chromosomes
recombine normally
Livernois et al., 2012
SEX CHROMOSOMES IN HUMANS
➢ Recombination is further
suppressed
➢ Proto-Y degrades; loss of
function of some genes
➢ Upregulation in males and
females
Livernois et al., 2012
SEX CHROMOSOMES IN HUMANS
➢ More upregulation in males
➢ Upregulation and
downregulation in females
➢ Genes with male-specific
function
Livernois et al., 2012
SEX CHROMOSOMES IN HUMANS
➢ Restriction of recombination
➢ Degeneration of the Y
➢ Male-specific role
➢ Overexpression and
inactivation of homologous
regions in females
Livernois et al., 2012
SEX CHROMOSOMES IN HUMANS
➢ Addition of an autosomal
segment
Livernois et al., 2012
SEX CHROMOSOMES IN HUMANS
➢ Differentiation/loss of
genes on Y
➢ Upregulation of the X copy
➢ Suppression of
recombination into the
added segment
Livernois et al., 2012
ORGANIZATION OF HUMAN SEX CHROMOSOMES
➢X-conserved region (XCR)
➢X-added region (XAR)
➢Pseudoautosomal region (PAR)
➢S1-S5: strata
X CHROMOSOME
Ellegreen et al., 2011
ORGANIZATION OF HUMAN SEX CHROMOSOMES
➢Pseudoautosomal regions
➢Male-specific region on Y (MRY):
➢Ampliconic regions
➢X-degenerated regions
➢X-transposed region
Y CHROMOSOME
Ellegreen et al., 2011
CONCLUSIONS
➢ Sex chromosomes originated from a pair of autosomes.
➢ Sex chromosomes have evolved independently many times in different lineages,they show common features (evolutionary convergence).
➢ In vertebrates, sex chromosome differentiation has followed the same path.
➢ The presence of a heterogametic sex leads to degeneration of one of the sexchromosomes.
➢Sex chromosome differentiation can be used in the phylogeny.
REFERENCES
Ellegren, H. (2011, March). Sex-chromosome evolution: Recent progress and the influence of male and female heterogamety. Nature Reviews Genetics, Vol. 12, pp. 157–166. https://doi.org/10.1038/nrg2948
Graves, J. A. M. (2016, January 1). Evolution of vertebrate sex chromosomes and dosage compensation. Nature Reviews Genetics, Vol. 17, pp. 33–46. https://doi.org/10.1038/nrg.2015.2
Hughes, J. F., & Rozen, S. (2012). Genomics and Genetics of Human and Primate Y Chromosomes. Annual Review of Genomics and Human Genetics, 13(1), 83–108. https://doi.org/10.1146/annurev-genom-090711-163855
Livernois, A. M., M Graves, J. A., & Waters, P. D. (2011). The origin and evolution of vertebrate sex chromosomes and dosage compensation AM Livernois, JAM Graves and PD Waters. 108. https://doi.org/10.1038/hdy.2011.106
Soh, Y. Q. S., Alföldi, J., Pyntikova, T., Brown, L. G., Graves, T., Minx, P. J., Page, D. C. (2014). Sequencing the mouse y chromosome reveals convergent gene acquisition and amplification on both sex chromosomes. Cell, 159(4), 800–813. https://doi.org/10.1016/j.cell.2014.09.052
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