Research reveals role of gene in i...( s produces the cells of sexual reproduc...)

s produces the cells of sexual reproduction, such as sperm cells and egg cells, which contain only a single strand of each of the organism's characteristic number of chromosomes. Later, when the mature sperm and egg cells combine, the new individual will have its full complement of DNA--half from the mother and half from the father. Much of the team's research is focused on the reshuffling of genetic material between two similar chromosomes, which occurs during meiosis when the double-stranded chromosomes in the cell's nucleus are pulled apart and brought together again twice by a team of proteins, resulting in four new male or female reproductive cells.

The researchers conduct their studies with a mutant strain of the model laboratory plant, Arabidopsis, in which the RAD51 gene is unable to function because a piece of foreign DNA is inserted in the middle of the gene. Ma's team dissected the plant's tiny flower buds before they had a chance to develop, when they were only about 0.3 or 0.4 millimeters in diameter. "It is important to look at the cells from the tiny flower buds before they open because meiosis is an event that occurs before pollen development starts," Ma explains. "We then treat the cells with chemicals that protect their structure from damage and then stain them with a chemical that allows us to see the DNA much more clearly than any other part of the cell.

The researchers' microscopic images of meiosis in their mutant plants revealed not neat chromosome packages but a chaos of many broken sections of chromosomes. "We found that plants in which the RAD51 gene does not function are not able to recombine the sections of their chromosomes that are broken during meiosis," Ma says. The researchers additionally tested this finding by introducing into the plants a mutation in a gene, named SPO-11, that disables the protein system that cuts chromosomes. "In plants that are defective in both SPO-11 and RAD51, we find intact chromo
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Contact: Barbara K. Kennedy
science@psu.edu
814-863-4682
Penn State
21-Jul-2004

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