Sequence of the chicken sex chromosomes
Name
654107223-MIT.pdf
Description
Full printable version
Size
20.94 MB
Format
Adobe PDF
Checksum (MD5)
722e027114546b4c416fb00d5a9011c4
Author(s)
Bellott, Daniel Winston
Advisor(s)
David C. Page.
Date Issued
2010
Publisher
Massachusetts Institute of Technology
Abstract
In birds, as in mammals, the chromosome complement determines sex. Male birds are designated ZZ, female ZW. Mammals have the opposite system; males are XY and females XX. Both the avian ZW and mammalian XY pair are believed to have evolved from autosomes, with dramatic changes, both gene loss as well as gene acquisition and amplification occurring on the sex-specific W and Y chromosomes. In contrast, Z and X chromosomes are assumed to have diverged little from their autosomal progenitors. The Z and W sex chromosomes of the chicken provide a unique opportunity to study the evolution of sex chromosomes in a second lineage with an alternate system of heterogamety. We produced the finished sequence of the chicken Z chromosome and generated female-specific markers necessary to produce a complete sequence of the chicken W chromosome. Already our analysis of the Z chromosome has revealed that the sex chromosomes of birds evolved independently of the sex chromosomes of mammals. Despite this independence, the chicken Z chromosome converged on a suite of features analogous to those of the human X chromosome: low gene density, an enrichment for interspersed repeats, and large multi-copy gene families expressed in the testis. These features arose during the evolution of the Z and X chromosomes as sex chromosomes, overturning the notion that Z and X chromosomes are evolutionarily stable. Our preliminary efforts on the W chromosome have provided insights into its structure and underscore the ubiquity of gene acquisition and amplification on vertebrate sex chromosomes. As we accumulate genomic data from additional sex chromosomes, explaining the evolutionary forces that result in gene acquisition and amplification will remain a major challenge.
Description
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biology, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references.
Subjects
Biology.
MIT Department
Massachusetts Institute of Technology. Department of Biology
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