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More About The Y Chromosome
The Y chromosome has been likened to a hall of mirrors because its sequence contains many sections that appear to be palindromes. These palindromes provide a clue to some interesting events in that may have occurred during the course of its evolution. Ordinary chromosomes have the ability to recombine with their paired partners as illustrated in the first section of this animation. The X and Y chromosomes are not able to recombine along their entire length. During the course of its evolution, the Y chromosome lost its ability to recombine with the X in its midsection ( illustrated in more detail in the evolution of the Y chromosome animation). The modern X and Y chromosomes recombine only at the tips. For years researchers consider the midsection of the Y to be a ìwastelandî populated largely by useless sequences. With the recent announcement of the completed Y chromosome sequence their came some suprising details about how the Y may be able to recombine with itself. The palindromic sequences suggest that the Y preserves the integrity of its genes by actually storing backup copies within itself. The animation shows that the Y chromosome may repair mutated genes by forming a loop and copying the gene from one arm to the other. There is also the likeliehood that a mutation could be copied in the same manner.
Web Resources
"The Book of Y: An Unfinished Story About Maleness"
Describes the research of David Page and other members of his lab.
http://www.hhmi.org/bulletin/bookofy/
Related HHMI Resources on BioInteractive.org
Meiosis Animation (Sex Determination)
http://www.hhmi.org/biointeractive/animations/
The Meaning of Sex: Genes and Gender
Lecture Four presented by David Page: "Sexual Evolution: From X to Y"
http://www.hhmi.org/biointeractive/gender/lectures.html
"Gender Testing of Female Athletes"
http://www.hhmi.org/biointeractive/gendertest/gendertest.html
References Used in Developing the Animation
Jegalian, K., and Lahn, B.T. 2001. Why the Y is so weird. Scientific American 284(2): 56–61.
Kuroda-Kawaguchi, T., Skaletsky, H., Brown, L.G., Minx, P.J., Cordum, H.S., Waterston, R.H., Wilson, R.K., Silber, S., Oates, R., Rozen, S., and Page D.C. 2001. The AZFc region of the Y chromosome features massive palindromes and uniform recurrent deletions in infertile men. Nature Genetics 29(3): 279–86.
Lahn, B.T., and Page, D.C. 1999. Four evolutionary strata on the human X chromosome. Science 286(5441): 964–7.
Lahn, B.T., Pearson, N.M., and Jegalian, K. 2001. The human Y chromosome, in the light of evolution. Nature Reviews Genetics 2(3): 207–16.
Credits
Director: Dennis Liu, Ph.D.
Scientific Direction: David Page, M.D.
Scientific Content: Donna Messersmith, Ph.D.
Animators: Chris Vargas, Eric Keller
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