Simple reason helps males evolve more quickly

November 14, 2007

GAINESVILLE, Fla. --- The observation that males evolve more quickly than females has been around since 19th century biologist Charles Darwin noted the majesty of a peacock's tail feather in comparison with the plainness of the peahen's.

No matter the species, males apparently ramp up flashier features and more melodious warbles in an eternal competition to win the best mates, a concept known as sexual selection.

Why males are in evolutionary overdrive even though they have essentially the same genes as females has been a mystery, but an explanation by University of Florida Genetics Institute researchers to appear online in the Proceedings of the National Academy of Sciences this week may shed light on the subject.

"It's because males are simpler," said Marta Wayne, an associate professor of zoology in the College of Liberal Arts and Sciences and director of UF's Graduate Program in Genetics and Genomics. "The mode of inheritance in males involves simpler genetic architecture that does not include as many interactions between genes as could be involved in female inheritance."

The finding may also be useful to scientists studying why diseases may present themselves or respond to treatment differently in men and women.

Researchers examined how gene expression is inherited differently in male and female fruit flies using microarray analysis, which is a way to monitor the activity of thousands of genes simultaneously. The flies were identical genetically, except that females have two X chromosomes and males have a single X and a single Y chromosome.

It turns out that the extra X in females may make answering the call of selection more complicated.

In flies or humans, sex cells from a mother and a father combine to make what eventually becomes an embryo. Females are equipped with two versions of X-linked genes that interact not only with each other, but also with other genes. Males have only one version of the X chromosome, making for fewer interactions and more straightforward male inheritance, especially since the male's Y chromosome contains very few genes.

"In females, a dominant allele can hide the presence of a recessive allele," said Lauren McIntyre, an associate professor of molecular genetics and microbiology in UF's College of Medicine. "In contrast to females, which have two X chromosomes, one inherited from each parent, males have only one X inherited only from their mother. This is a simple mechanism that could be working in cooperation with sexual selection to help males evolve more quickly."

Researchers believe this relatively uncomplicated genetic pathway helps males respond to the pressures of sexual selection, ultimately enabling them to win females and produce greater numbers of offspring.

Relationships between gene expression and modes of inheritance have been addressed before, but this study analyzed an extremely large data set that involved most of the genes in the fruit fly genome, said David Rand, a professor of biology at Brown University who was not involved in the study.

"This research shows how recessive and dominant traits are important in determining variation in populations," Rand said. "The best way to think of it is males play with one card, but females get to play one and hold one. If males have got a good trait, it's promoted; something bad, it's eliminated. In females you can have a bad card, but a good card can protect it. As a result, females can carry deleterious traits but not express them."

UF scientists analyzed 8,607 genes that are shared by both sexes of a fruit fly called Drosophila melanogaster. Of those genes, 7,617 are expressed differently -- meaning the same genes do different things -- in males and females.

Over the years, fruit fly research has helped scientists understand the role of genes in diseases, development, population genetics, cell biology, neurobiology, behavior and evolution. Humans share more than 65 percent of their genes with the fruit fly, including many implicated in certain cancers, Alzheimer's disease and heart disease.

The finding helps explain fundamental processes that may factor into why men and women may show different symptoms or respond differently to diseases.

"There's a health aspect in figuring out differences in gene expression between the sexes," said Wayne. "To make a male or a female, even in a fly, it's all about turning things on -- either in different places or different amounts or at different times -- because we all basically have the same starting set of genes."
-end-
The research was supported by a National Institutes of Health grant. Scientists from the University of Nebraska, Ohio University, the University of California Davis and the University of Southern California were also involved in the study.

University of Florida

Related Genetics Articles from Brightsurf:

Human genetics: A look in the mirror
Genome Biology and Evolution's latest virtual issue highlights recent research published in the journal within the field of human genetics.

The genetics of blood: A global perspective
To better understand the properties of blood cells, an international team led by UdeM's Guillaume Lettre has been examining variations in the DNA of 746,667 people worldwide.

Turning to genetics to treat little hearts
Researchers makes a breakthrough in understanding the mechanisms of a common congenital heart disease.

New drugs more likely to be approved if backed up by genetics
A new drug candidate is more likely to be approved for use if it targets a gene known to be linked to the disease; a finding that can help pharmaceutical companies to focus their drug development efforts.

Mapping millet genetics
New DNA sequences will aid in the development of improved millet varieties

Genetics to feed the world
A study, published in Nature Genetics, demonstrated the effectiveness of the technology known as genomic selection in a wheat improvement program.

The genetics of cancer
A research team has identified a new circular RNA (ribonucleic acid) that increases tumor activity in soft tissue and connective tissue tumors.

New results on fungal genetics
An international team of researchers has found unusual genetic features in fungi of the order Trichosporonales.

Mouse genetics influences the microbiome more than environment
Genetics has a greater impact on the microbiome than maternal birth environment, at least in mice, according to a study published this week in Applied and Environmental Microbiology.

New insights into genetics of fly longevity
Alexey Moskalev, Ph.D., Head of the Laboratory of Molecular Radiobiology and Gerontology Institute of Biology, and co-authors from the Institute of biology of Komi Science Center of RAS, Engelgard's Institute of molecular biology, involved in the study of the aging mechanisms and longevity of model animals announce the publication of a scientific article titled: 'The Neuronal Overexpression of Gclc in Drosophila melanogaster Induces Life Extension With Longevity-Associated Transcriptomic Changes in the Thorax' in Frontiers in Genetics - a leading open science platform.

Read More: Genetics News and Genetics Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.