- •М инистерство образования и науки Российской Федерации южно-уральский государственный университет
- •Text 2 Вопросы народонаселения
- •Text 3 factors of poverty
- •Text 4 Marry your like
- •Text 5 По данным опроса
- •Text 7 Вопрос о положении женщин
- •Text 8 Aids is back on message
- •Text 10 The Second Stage
- •Texts for sight translation Text 1 Russia facing difficult social problems
- •Text 5 Feeling wanted
- •Text 7 Aids in Russia
- •Ecology
- •Vocabulary
- •Texts for written translation Text 1 The Greenhouse Effect
- •Text 2 Now What?
- •Text 4 The deadliest place on Earth
- •Text 5 Climate change issue shows how little we care about our planet
- •Text 6 Rapid human population growth spells more trouble for environment
- •Text 7 Could power plants of the future produce zero emissions?
- •Text 8 Climate and the rise of men
- •Texts for sight translation Text 1
- •Is climate change really inevitable?
- •Text 2 Ecological problems - True crisis of humanity
- •Text 3 Clean energy - Earth's only chance against global warming
- •Text 4 Wildlife management - Definition and its main role
- •Text 5 Report suggests slowdown in co2 emissions rise
- •2010 Showing record temperatures
- •Education General vocabulary
- •Texts for written translation Text 1 The Bologna process
- •Text 2 Что такое "Болонский процесс"?
- •Text 3 Universities go to market
- •Is college worth it? Too many degrees are a waste of money. The return on higher education would be much better if college were cheaper
- •Text 5 Есть мнение
- •Text 6 Rooting out student cheats
- •Text 7 а заграница лучше
- •Text 8 Examinations for sale
- •Text 9 Язык до карьеры доведет
- •Text 10 Another country
- •Texts for sight translation Text 1 Murphy’s law
- •Text 2 British Students Protest Tuition Hikes
- •Text 3 Portrait of the student as a young swot
- •Text 4 University today
- •Vocabulary
- •Investigation
- •Texts for written translation Text 1 Crime and Punishment
- •Text 2 Defiant Khodorkovsky denies all charges
- •Text 3 Ирония судьбы
- •Text 5 Война ведь
- •Hijacked Jets Destroy Twin Towers and Hit Pentagon
- •Text 9 Трагедия в церкви
- •Text 10 Down with the Death Penalty
- •Texts for sight translation Text 1 Kholodov Appeal Rejected
- •Text 2 Human trafficking and slave trade
- •Text 3 Attorney jailed in Spanish probe
- •Text 4 Too immature for the death penalty?
- •Text 5 An end to killing kids
- •Mass Media
- •Texts for written translation Text 1 Russian Television in the era of managed media
- •Text 2 The golden years
- •Text 3 The nineties
- •Text 4 Today
- •Text 5 Как сделать новости правильными Text 6
- •Text 7 San Francisco center keeps muckraking alive
- •Text 8 The center for investigative reporting
- •Text 9 Новый жанр публицистики
- •Text 10 When Love Backfires
- •Texts for sight translation Text 1 Overview
- •Text 2 To join the elite it’s tv that counts
- •Text 3 Sweden Pushes Ban on Children’s Ads
- •Science
- •Vocabulary
- •Text 4 The New Role of Microbes in Bio-Fuel Production
- •Text 5 Scientists Build a Custom Chromosome
- •Text 6 Scientists Revisit Power from Potatoes
- •Text 7 New Earth-Size Planet Found
- •Text 8 Male or female? First sex-determining genes appeared in mammals some 180 million years ago
- •Texts for sight translation Text 1
- •Text 2 Briton, Japanese Share Nobel Prize for Medicine
- •Text 3 Google Plans New Solar Mirror Technology
Text 8 Male or female? First sex-determining genes appeared in mammals some 180 million years ago
April 23, 2014
Male or female? In humans and other mammals, the difference between sexes depends on one single element of the genome: the Y chromosome. It is present only in males, where the two sexual chromosomes are X and Y, whereas women have two X chromosomes. Thus, the Y is ultimately responsible for all the morphological and physiological differences between males and females.
But this has not always been the case. A very long time ago, the X and Y were identical, until the Y started to differentiate from the X in males. It then progressively shrank to such an extent that, nowadays, it only contains about 20 genes (the X carries more than one thousand genes). When did the Y originate and which genes have been kept? The answer has just been brought to light by the team of Henrik Kaessmann, Associate Professor at the CIG and group leader at the SIB Swiss Institute of Bioinformatics, and their collaborators in Australia. They have established that the first "sex genes" appeared concomitantly in mammals around 180 million years ago.
By studying samples from several male tissues - in particular testicles - from different species, the researchers recovered the Y chromosome genes from the three major mammalian lineages: placentals (which include humans, apes, rodents and elephants), marsupials (such as opossums and kangaroos) and monotremes (egg-laying mammals, such as the platypus and the echidna, a kind of Australian porcupine). In total, the researchers worked with samples from 15 different mammals, representing these three lineages, as well as the chicken, which they included for comparison.
Instead of sequencing all Y chromosomes, which would have been a "colossal task" according to Diego Cortez, researcher at CIG and SIB and main author of the study, the scientists "opted for a shortcut." By comparing genetic sequences from male and female tissues, they eliminated all sequences common to both sexes in order to keep only those sequences corresponding to the Y chromosome. By doing so, they established the largest gene atlas of this "male" chromosome to date.
This study required more than 29,500 computing hours! A gigantic task, which could not have been performed without important technical means: the high-throughput DNA sequencers of the genomics platform at the Center for Integrative Genomics, for the generation of the genetic sequences, and the calculation means of Vital-IT, SIB's high-performance computing centre, for the biological analyses.
The study shows that the same sex-determining gene, named SRY, in placentals and marsupials had formed in the common ancestor of both lineages around 180 million years ago. Another gene, AMHY, is responsible for the emergence of Y chromosomes in monotremes and appeared some 175 million years ago. Both genes, which according to Henrik Kaessmann are "involved in testicular development," have thus emerged "nearly at the same time but in a totally independent way."
The nature of the sex-determination system present in the common ancestor of all mammals remains unclear, given that mammalian Y chromosomes did not yet exist at that time -- at least not those discovered in this study. So what triggered back then that an individual was born male or female? Was this determination linked to other sex chromosomes, or even environmental factors such as the temperature? The latter is not an unreasonable scenario, given that temperature determines sex in present-day crocodiles. As far as mammals are concerned, "the question remains open," concludes Diego Cortez.