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Female Embryonic Sexual Development Driven By Universal Factor:

A gene essential to the growth and development of most organ systems in the body also is vital to female - but not male - embryonic sexual development, scientists report this month.

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In the early days of research into sexual development, it was thought that all females had two X chromosomes, all males had an X and a Y, and that the Y made all the difference. Unless it had a Y chromosome, an embryo developed ovaries and became female, more or less by default, scientists thought. They even found a specific gene on the Y chromosome, called SRY (for sex-determining region of the Y chromosome) that appeared to be essential for testes formation.

But when researchers discovered some rare cases of individuals who developed testes even though they had two X chromosomes and no Y chromosome or SRY gene, they realized that the mechanisms of sex determination were more complex than previously thought.

This led to a new theory, called the "Z" hypothesis, which proposed that testes development was actually the default pathway. According to this theory, an unknown gene or process, called "Z," could disrupt this pathway and lead to the development of ovaries.

Why Shar Pei Dogs Have So Many Wrinkles:

A group of researchers at Universitat Autònoma de Barcelona (UAB) have discovered the origin of the mucinosis present in Shar Pei dogs, a hereditary disorder responsible for the characteristic wrinkles found in this breed.

Early Development Of Antibodies To Cockroach And Mouse Proteins Associated With Greater Risk For Asthma And Allergies In Preschool Children:

A study released by researchers at the Columbia Center for Children's Environmental Health (CCCEH) at Columbia University's Mailman School of Public Health shows that developing antibodies to cockroach and mouse proteins is associated with a greater risk for wheeze, hay fever, and eczema in preschool urban children as young as three years of age.

Low Concentrations Of Pesticides Can Become Toxic Mixture For Amphibians:

Ten of the world's most popular pesticides can decimate amphibian populations when mixed together even if the concentration of the individual chemicals are within limits considered safe, according to University of Pittsburgh research.

Parasite-resistant Peppers Green Alternatives To Chemical Pesticides:

Root-knot nematodes are extreme parasites. These microscopic, omnipresent worms cause major damage to horticultural and field crops in sub-tropical regions, resulting in significant financial losses to growers and gardeners.