Can yellow, obese Agouti mice have brown pups or are they all yellow?

-An undergraduate from Utah

April 7, 2011

Yes fat, yellow mice can have thin brown pups. Even if their genes make it look impossible.

How can the pups be brown when their genes tell them to be yellow? By the environment marking the genes involved and changing how they work.

Before getting into this, let's first talk about the genes involved in how pups end up yellow or brown. Then we can delve deeper into how the environment can change how a gene works.

Yellow is Dominant

Agouti is one of the key genes involved in making a mouse brown or yellow. Small differences in the versions of the agouti gene cause differences in colors or hair patterns. So one version, the dominant agouti gene (A), directs cells to make the yellow pigment and the recessive version (a), tells them to make a brown pigment instead.

For example, scientists have found that changing the diet and toxins that pregnant mice are exposed to can change the expression of the agouti gene in their pups. So in addition to the genes the moms hand down to their offspring, they also pass an 'epigenome' along. And the epigenome depends on what the moms are exposed to in their environment.

When scientists fed pregnant yellow mice diets rich in nutrients containing methyl-groups, like folic acid and vitamin B12, the agouti gene in pups got switched off. And the pups from such mice were brown and thin, not fat and yellow.

My boyfriend has 3 sisters whereas I have 2 sisters and no brothers. What are the chances of him and I having a baby boy?

-A high school student from Trinidad and Tobago

October 12, 2004

This is a really great question that we get a lot in one form or another. The quick answer is that your chances of having a boy are most likely the same as everyone else's.

This is because the odds of something happening apply to each time it happens -- it doesn't matter what came before. Let's use flipping a coin as an example.

How is it that DNA can be extracted and read from long past fossils? Doesn't the drying and age affect the DNA? If we can clone a sheep from its DNA, why not a dinosaur?

-A curious adult from California

October 5, 2004

What fun questions. DNA is actually pretty stable for a biological molecule, particularly under conditions that are dry, cold and airless. DNA won't last forever, but it can last a long, long time.

However, it won't survive intact. What happens is that the ridiculously long strands of DNA break into smaller and smaller pieces over time. After an even longer time, the pieces begin to break more and more until eventually there is very little left.

My 27 year old son died in March 2004. He was quadriplegic due to an assault 6 years ago. The hospital said he had a septic infection. He was awake and talking and then they were putting on a respirator and his heart stopped. They got it going t

-A curious adult from Minnesota

I am so sorry about the loss of your son. Most likely the DNA from your son won't be able to tell you why your son died; at least not now with our current knowledge.

Since I'm not a medical doctor I won't comment specifically on the cause of your son's death. However, the fact that he had a bacterial infection when he was admitted to the hospital is suggestive. Testing your son's DNA will not provide much information about the infection itself. But it might help us understand why it hit him so hard.

I was born in Maine. Can a DNA test establish Native American blood? Would it be enough to file for Native American heritage? Hello. I am a 30 year old woman from Stockton, California. A lot of people have told me that the bone structure by my temp

-Curious adults from California and Guam

September 28, 2004

The quick answer is that yes, you can determine whether you have ancestors who are Native American through your DNA. I don't know whether it would be enough to file for Native American heritage though.

What scientists would look at is your mitochondrial DNA (mtDNA) and, if you are a male, your Y chromosome. Even if you are not a male, you can look at your dad's, uncle's, or brother's Y chromosome to get an answer.

I recently read that the male Y chromosome used to have 1,438 genes, and only has 45 now. If the chromosome continues to degrade, are men going to go extinct?

- A curious adult from California

September 22, 2004

This is an active area of debate right now with no clear answer. Some predict that within a few hundred thousand years, the Y chromosome will disappear completely (along with people if evolution or scientists don't do something about it). Other people think it has stabilized and will be around for a long time to come.

When I was a camp counselor a few years back, one of the campers had light hair and a green eye with lighter eyelashes/eyebrows on one side and darker hair and a brown eye with darker eyelashes/eyebrows on the other. Also the lighter side had more

- A curious adult from Georgia

September 16, 2004

Sounds to me like your camper was either a mosaic or a chimera. Given her differences, the most likely answer is chimera.

Chimeras and mosaics are people who have two sets of cells in their body, each with different DNAs. Mosaics are very common, chimeras are though to be very rare.