An individual’s genetics are a random and unique combination of the mother’s genetic code, and half of the father’s.
William and Ivar Gunderson, second and first year law students at the University of Idaho, are brothers.
They are both tall, square and blue-eyed, but most people tell them their smile makes them look alike, William Gunderson said.
“We both got best smile in high school,” William Gunderson said. “People recognize us by our smile, I think.”
Ivar Gunderson said their dad is about 6 feet, 4 inches tall, but their mom is about 5 feet, 5 inches tall.
Their mother has brown eyes, and their father has blue eyes. Three of the four Gunderson sons inherited blue eyes, even though brown irises are dominant, according to Barrie Robison, a UI biology professor.
“For the most part, the alleles that produce brown pigment, are what are called dominate over the blue pigment,” Robison said. “You need two copies of where the brown pigment doesn’t work to have the blue eye thing revealed.”
Robison said traits are called phenotypes by geneticists.
“Brown hair is a phenotype — (as are) blue eyes,” Robison said. “Some of these phenotypes are straight forward in their classification.”
These are known as Mendelian traits.
“Mendel was the guy that kind of came up with that model of inheritance,” Robison said. “These are things such as detached earlobes — no detached earlobe.”
Other traits, such as eye color, are figured on a gradient scale.
“Are all blue eyes the same?” Robison said. “No. You have very dark brown eyes, but there are other people that have brown eyes that are lighter.”
The cellular level
Each cell has 46 chromosomes — tightly coiled sticks of DNA.
“We are called diploid,” Robison said. “And that means for any particular gene in your genome, you have two copies.”
Twenty-three chromosomes come from the mother and another 23 from the father.
Each version of a certain gene is called an allele.
When a gamete — a sperm or an egg — is formed, the original cell splits and those two split again, but only one copy — an allele — of each gene goes to each daughter cell.
This random process could make every gamete different, yet alike. When a sperm meets and fuses with an egg, the resulting cell will have a new set of alleles that are like the parents’ but different from them.
“This is why brothers and sisters can often have different traits, because mom might actually be carrying two alleles for that trait, and dad might be carrying two different alleles, and it’s a matter of which combinations you get,” Robison said. “That’s why for some traits, brothers and sisters are really similar, and for other traits, it’s like ‘Whoa, you have red hair and I don’t, what happened?'”
Ivar Gunderson takes after his meticulous father, the brothers said.
“Ivar’s been pretty meticulous about setting up a hot wire for our pastures,” William Gunderson said. “And did a little project with a fertilizer in the past year.”
“Yeah, well, we all kind of did that,” Ivar Gunderson said.
“But you were the one that made the fertilizer spreader,” William Gunderson said. “He went out and got a big tank on wheels and Ivar designed the spray system.”
William Gunderson said he is more like his mother’s side of the family.
“Not that it’s a bad thing, but sometimes I have a tendency not to be punctual, and that sometimes was a problem kind of growing up,” William Gunderson said. “Our mom was always in a rush to take us places — make sure we were on time because we were always last-minute. And I’m kind of that same way.”
“You didn’t inherit any of her cooking traits though,” Ivar Gunderson said.
Quantitative traits
“Let’s take height,” Robison said. “Would you agree that tall parents tend to have tall kids? Generally — on average.”
These kind of scalable traits are called “quantitative traits.”
“Because they can be measured on a quantitative — I can measure your height to the nearest nanometer,” Robison said. “With people, there (are) actually lots and lots of different forms of eye color.”
Quantitative traits use different models and framework, he said.
“The problem is these traits are influenced by lots of genes,” Robison said. “And so you get a big bunch of different alleles from mom, and a bunch of different alleles from dad, and how they work in concert, is what determines your height.”
Environment and nutrition also factor into quantitative traits.
William Gunderson said they both care about a clean apartment.
“We run a pretty tight ship around our apartment,” William Gunderson said. “We try to make sure everything’s neat and orderly, I guess.”
But they are different when it comes to trying new things, he said.
“Ivar’s learning how to rock climb, right now,” William Gunderson said. “He’s bought a bunch of equipment – a bunch of gear for doing that. He takes it pretty seriously, whatever it is. I’m a little more comfortable with sticking to the things I know.”
Joanna Wilson can be reached at [email protected]