Bob McDonald is one of Canada’s best known science journalists, bringing science to the public for more than 40 years. In addition to hosting Quirks & Quarks, the award-winning science program that is heard by 500,000 people each week, McDonald is also science correspondent for CBC TV’s The National and host and writer of the children’s series Head’s Up.

His latest post dives deep on some classic holiday science mysteries, like what kind of heart condition could be behind the Grinch’s actions and the possible DNA-based phenomena behind Rudolph’s red nose. Here are some excerpts:

Heart two sizes too small?

“No one quite knows the reason,” the story goes.

“It could be, perhaps, that his shoes were too tight.

It could be his head wasn’t screwed on just right.

But I think that the most likely reason of all

May have been that his heart was two sizes too small.”

People can be born with a heart that is too small, which surgeons usually need to correct.

Cardiology professor David Kass of Johns Hopkins Hospital in Baltimore, Md., said hypertrophic cardiomyopathy produces an abnormally walled heart. The pumping organ becomes too small because an inner wall thickens from the outsides inwards.

Kass says when there’s less space in the heart then it needs to beat faster. Exercising can become a problem. That’s why teenage boys are sometimes discovered to have the disease when they collapse while playing sports.

To have a better idea of what caused Grinch’s small heart, Kass needs to be able to examine Grinch and his medical history such as blood pressure.

Growing heart diagnosis

But the Grinch’s sudden embrace of the Christmas spirit was also attributed to a puzzling condition: the spontaneous growth of this heart by  “three sizes,” just in time to return everything he took and carve the festive roast beast.

For that, heart failure immediately came to Kass’s mind.

“People get weak hearts have a heart attack and the heart will get big and it can get big pretty quickly because that’s what the body wants to do to it. The downside of that is that you don’t feel good. You going to feel tired, and as I recall from the book, the Grinch’s heart gets big, but he’s actually lifting his sled at the same time and zipping down the hill and heading back to Whoville and he’s all happy,” Kass tells Quirks & Quarks host Bob McDonald.

“This is not someone with heart failure.”

…

Rudolph’s mom and a coral

As for the enduring Christmas mystery surrounding Rudolph’s nose, Dr. Steven Farber from Johns Hopkins University dug into the inexplicable plot line.

Farber, a principal investigator at the Carnegie Institution for Science and a biology professor, says researchers make proteins glow red in the lab.

Farber gives the example of the protein collagen in skin.

“We could take the DNA sequence where collagen is made in the gene, in the DNA, and insert a DNA sequence to make a red protein inside that collagen gene. So then the skin could grow glow red and the DNA to make red colours comes from jellyfish and sea creatures. And so we can kind of splice that if you will into the genome of the fish and then it will light up.”

Cut and paste DNA

What’s trickier is how a gene for glowing red could end up in Rudolph’s nose.

If for example Santa’s sleigh crashed into the Red Sea where there is anthazoin corals while Rudolph’s mother was pregnant then perhaps she struck a coral and its DNA got into her embryo, Farber says.

Biologists recognize how virus-like “mobile genetic elements” can insert their DNA into the host.

“Something a lot of folks don’t realize is most of our DNA is remnants of these kinds of mobile elements,” Farber says. “So if for example this DNA was somehow incorporated into a mobile element like a transposable element, it could kind of cut and paste and insert it in the genome.”

 To read the complete rundown of these eye-opening explainers, visit the Quirks and Quarks page.