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takyon writes:

Male Y Chromosomes Not "Genetic Wastelands"

When researchers say they have sequenced the human genome, there is a caveat to this statement: a lot of the human genome is sequenced and assembled, but there are regions that are full of repetitive elements, making them difficult to map. One piece that is notoriously difficult to sequence is the Y chromosome.

Now, researchers from the University of Rochester have found a way to sequence a large portion of the Y chromosome in the fruit fly Drosophila melanogaster—the most that the Y chromosome has been assembled in fruit flies. The research, published in the journal GENETICS [open, DOI: 10.1534/genetics.118.301765] [DX], provides new insights into the processes that shape the Y chromosome, "and adds to the evidence that, far from a genetic wasteland, Y chromosomes are highly dynamic and have mechanisms to acquire and maintain genes," says Amanda Larracuente, an assistant professor of biology at Rochester.

[...] Using sequence data generated by new technology that reads long strands of individual DNA molecules, [PhD student Ching-Ho] Chang and Larracuente developed a strategy to assemble a large part of the Y chromosome and other repeat-dense regions. By assembling a large portion of the Y chromosome, they discovered that the Y chromosome has a lot of duplicated sequences, where genes are present in multiple copies. They also discovered that although the Y chromosome does not experience crossing over, it undergoes a different type of recombination called gene conversion. While crossing over involves the shuffle and exchange of genes between two different chromosomes, gene conversion is not reciprocal, Larracuente says. "You don't have two chromosomes that exchange material, you have one chromosome that donates its sequence to the other part of the chromosome" and the sequences become identical.

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