According to a new study, papaya may contain the secret of sexual chromosome evolution. "This is the first time we have recorded the differentiation to the XY chromosome system at the initial stage. Molecular biologist Ray Ming said papaya capapaya is an unusual plant because it has three sexes - male, female and hermaphrodites. Each individual's flowering is different. Over the past decades, the weird sex determination system of papaya has attracted the interest of many scientists. For the papaya grower in Hawaii, the sex of papaya also has an important economy. Value, because the customer prefers the fruit of the monoecious papayas.Now molecular biology techniques reveal three methods of genetic mapping using secretive use of papaya sex, and Ming and his colleagues at the Hawaii Agricultural Research Center identified a decision. A small fragment of DNA of the male sex.This region accounts for about 10% of the chromosome and only exists in the male and female plants of papaya.Different from the Y chromosome in animals and a few other plants, the size of this DNA fragment seems to be It is the same size as the DNA fragment that corresponds to the X chromosome, but like the Y chromosome in animals, this male region looks like Some of the protein-encoding DNA has been lost; this loss is often thought of as a step in the differentiation of the Y chromosome from the X. The scientists believe that the differentiation of the XY chromosome is achieved by suppressing recombination, in which the chromosomes of the association are crossed. The parent's genetic material was recombined to produce new recombinants. Ming's team found no recombination in the male chromosomal region of the 2190 papaya, further suggesting that it was an initial sex chromosome. Sex chromosomes are usually considered to be autosomal. Evolved, the male papaya region is very small, and the proportion of defective genes (about 38%) is lower than the proportion of human Y chromosome (95%), this finding shows that the male region of papaya is just starting from the autosomal Differentiation: "Papaya's male-specific region may be similar to the ancestor of the Y chromosome of 240 million to 320 million years ago. "The researchers published the results of the study on Nature, dated January 22, 2004. However, not all people are convinced by the results of this study. Evolutionary geneticist Dmitry Filatov of the University of Birmingham, UK, warned that although this article looks It seems very convincingly that papaya does exist on the sex chromosomes... but the story of evolution is less clear-cut.†Filatov said he would be happy to see the papayas and other XY chromosomes that have not yet differentiated. Comparison results between.
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