Why Y? Evolutionary biologist Dr Melissa Wilson Sayres joins RealScientists

As we observed in a post mid-last-year: sex is bizarre. In an evolutionary sense, in particular. Despite sexual dimorphic species existing throughout animal kingdom, there isn’t a lot in common between the ways different animals – for instance birds, reptiles, mammals – trigger the development of male vs female embryos. Mammals, as we know, use the inheritance of the sex chromosomes X and Y to determine sex – XY embryos typically develop as males, XX as females. The sex-determining region on the Y chromosome (Sry) was defined in the late 80s and shown to be necessary and sufficient to drive male development in mammals in the early 90s; apart from some defects in sperm production, XX mouse embryos (chromosomally female) which are ‘transgenic’ for an introduced copy of the Sry gene develop as normal males. Which raises the question – so what’s the rest of the Y chromosome for? It’s tiny (compared to other chromosomes), carries few genes, and the main job it has to carry out – determining maleness – can be done by one gene.

MelissaWilsonSayresThis is a question of particular interest to this week’s curator, Dr Melissa Wilson Sayres of UC Berkeley. Melissa’s research uses bioinformatics and genomics to study the evolutionary dynamics of sex chromosome evolution, male mutation bias, and pregnancy. Recently she published work in PLoS Genetics showing that human Y chromosomes are much more similar to each other than expected, and that this is because natural selection is acting to maintain the useful gene content that still survives there. Rumours of the Y chromosome’s demise are, it appears, somewhat exaggerated. “After that initial loss of genes, the primate lineage has been whittled down to a core set of genes that are necessary in humans for function,” Melissa told The Huffington Post. “Although there was initially a huge loss of genes from the Y chromosome, that rate of loss has transitioned from a gush to a trickle, and we expect that there will not be much more loss from the human Y chromosome.”

Aside from her research interests in evolutionary genetics, Melissa is also an advocate for science outreach advocate, having spearheaded several efforts to communicate science to the public including developing the content and infrastructure for a bi-annual workshop to introduce teenage girls to diverse scientific disciplines that has now been running for seven years, and organizing hands-on science activities for over 10,000 participants at the National Science and Engineering Festival. In addition to increasing appreciation of science among youth, Melissa is a vocal advocate for evolution education at all levels. She writes about her own science and other primary research articles for the public on her blog, mathbionerd.blogspot.com, and discusses evolution with anyone who wants to engage at pandasthumb.org. She tweets at @mwilsonsayres, apart from this week, when she’s tweeting for us!

Can you tell us a little bit about yourself?

I was born in Stillwater, Oklahoma. I lived in Oklahoma for five years, then to Garland, Texas, then Tempe, Arizona, then to Syracuse, Nebraska (yes, such a place exists, where I graduated high school with 43 people. I majored in Mathematics at Creighton University in Omaha, Nebraska. Then, I drove ~1,025 miles East on I-80 to attend graduate school in Integrative Biology: Bioinformatics and Genomics at The Pennsylvania State University in State College, PA. After graduate school, we (my husband – a physical chemist, our 5 month old daughter, and our adopted Chihuahua-mix) piled in the car and drove the 3,000+ miles West on I-80 for postdoctoral positions at UC Berkeley.

So how did you end up in science?

I always liked math. For awhile I just liked doing it, and thought I was good at it. During high school, I started to worry that I was particularly good at it, but I liked it, so I kept taking course after course. Then, in college, I majored in math. The summer between my junior and senior year of college I did a research experience for undergraduates (REU) in the Math department at the University of Nebraska, Lincoln in “Math Biology.” We modeled tumor growth to the point of metastasis using a series of differential equations, and something clicked. For the first time I really appreciated Biology, outside of the pre-med scheme. That year I applied to graduate programs and decision day came down to choosing between a program in pure mathematics and a program in bioinformatics. I choose the program in bioinformatics and can say that I found what I love to do. Even so, it took a few rotations to find my particular motivation in science. First, I worked growing yeast (the lab smelled amazing) and studying how proteins interacted with their chromatin. Then, I learned about microRNA in the mustard weed, Arabidopsis. Finally, I did a rotation studying sex chromosome evolution, and I was hooked. For now, and forever.

What is is about evolutionary biology that interests you?

The sex chromosomes are pretty amazing for a lot of reasons: the spend different amounts of time in the male and female germ lines, they carry a unique set of genes, they evolve following different patterns that the non-sex chromosomes, selection acts differently there, they are involved in sex determination, they used to look identical but now are very different, and on and on!


How did you end up in outreach? What’s been the highlights of that side of your work?

I can’t help myself. I like talking about my research, and about science in general wherever I am. If I’m on a plane, I bring up my work. Today I was at a toddler birthday party and I talked about armadillos with the adults, and explained pollen to the kids. Now, I still talk to whomever I’m with, but I also write about my field of science (both my own research and the research of others) at my own blog: mathbionerd.blogspot.com, and at pandasthumb.org. I get a lot more discussion and tangents at the latter, especially from people who don’t accept that evolution happens.

I started doing formal outreach during graduate school. I had just joined the local Graduate Women in Science (GWIS) group, and together with another grad student, we put together a day-long workshop to help a local girl scout group earn a badge in Engineering. Afterwards I was hooked and put together the infrastructure to recruit more troops, and to run bi-annual workshops, that are still being continued three years after I’ve left: http://www.clubs.psu.edu/up/gwis/GSW.html.

In a similar vein, I organized an activity, and volunteers from across the US, to teach the ~10,000 people about polymer chemistry at the USA Science and Engineering Festival. Here’s a picture of us, making about half of the 10,000 samples: http://mathbionerd.blogspot.com/2010/10/4354.html

I also have worked with local high schools, both in Pennsylvania and California, judging science fairs, and talking to Biology classes. Most recently I’ve ran an activity teaching the basics of phylogenetic analysis: http://mathbionerd.blogspot.com/2012/04/teaching-phylogenetics.html.

So what’s next for you and the family?

Now, with a few months left on our postdoctoral positions, we do not yet know where we will be, other than our lease ends, and we won’t be staying in California. I’ll be sure to share whenever I know!

We wish Melissa all the best with the job search, and for her week of curation on RealScientists!


James is a recovering scientist and escaped postdoc who works in research management at the University of Otago, New Zealand. He's now retired from active @RealScientists duty, after serving from the project's beginnings in 2013 through to mid 2015. When not managing research, surviving #PlanetParenthood or pretending not to be an expat Australian in the Deep South of NZ, he tweets @theotherdrsmith.

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