Blessed are the meek: for they shall inherit the earth.
Matthew 5:5, KJV
Have you ever wondered why you have brown hair and not blond? Or why you have green eyes while your brother has blue? Or why it is that chickens always come out of chicken eggs and never those from a duck? All of these questions have been asked by scientists for thousands of years, and in the last two centuries, we have made amazing advances in answering those questions in a field of science known as genetics.
If you were to visit the house of the dogs in the Kingdom of Animals, you would be greeted with many licks and THEN you could take a look at your favorite dog. (What kind? I like Border Collies.) If you zoomed in really, really, really close onto her skin, you would see the skin cells (of course). And if you looked even more closely at the nucleus of those cells, you might see in some of them a bunch of little x-shaped squiggles. Those squiggles are called chromosomes; they are long strands of DNA that sometimes curl up into those x-shapes. At other times, they are just long, jumbled threads or even look like beads along a string.
Different types of creatures have a different number of chromosomes, ranging in animals from 1 (in male Jack jumper ants) to 452 (for Atlas blue butterflies). Humans are in the middle of pack with 46 chromosomes, while our dog friend has a whopping 78. (The number of chromosomes has essentially no bearing on the complexity of the creature. The creature with the greatest number of chromosomes is a single-celled protist with an astonishing 16,000 chromosomes.) Since they are made of DNA, they of course carry the genetic information of the dog – the instruction that tell her body how to work. Each chromosome is made up of many sets of DNA called genes – sections of DNA that tell the body how to make a particular protein or how often to make new cells or a million other things.
Gregor Mendel, an Austrian priest and scientist, made an astounding breakthrough on understanding how our genes make us the way we are. By carefully studying pea plants (and, I mean, a lot of pea plants – around 20,000!) and doing some serious math, he figured out that the type of genes that the peas have (known as their genotype) does in fact determine what they look like (known as the phenotype). Not only that, but he discovered that some genes are stronger than others!
Imagine that you have two teams of wrestlers, Team Bear and Team Mouse, as in a team of bears and a team of mice that are going to go head-to-head. That doesn’t seem very fair! If you put someone from Team Bear in the ring with someone from Team Mouse – who will win? The bear, every single time. If two bear team members go head-to-head, of course it will be a bear who will win; same with two mice facing off. In fact, the only way that Team Mouse will win is if it is mouse vs. mouse.
It’s the same way with the dog’s genes. Each of its genes has two parts – one from her mother and one from her father. Let’s say that the floppy-ear gene is the strong team (what we call the dominant gene), while the perky-ear gene is the weak team (or recessive gene). If she got any floppy-ear genes from her parents, her phenotype (what she looks like) will be floppy-eared, even if she has one floppy-ear and one perky-ear gene. The only way that she will have perky-ears is if she gets that gene from both parents. Surprisingly, it is possible that she could have perky ears even if neither of her parents has perky-ears; recessive genes can hide behind dominant genes, even for generations, only to reappear later. Usually, you will see one creature with the recessive trait for every three with the dominant one.
Most of our phenotypes (such as our skin, hair, and eye color) are determined by more than one gene, making it much more difficult to predict what you will look like based on your parents. We do have a few simple genes which pass down much the same way Gregor Mendel predicted, such as the dominant traits of having earlobes that dangle free, freckles, a second toe longer than the first, dimples or the ability to roll your tongue to look like a hot dog bun. Look around your family and see what kind of features you have inherited from your parents or grandparents!
What about bacteria and archaea? Do they have any of these features? They do have DNA, as I am sure that you remember, and they do have genes since those are just sections of DNA that do something in particular. Their DNA does not form up into chromosomes, however. Still, their phenotype is determined by their genotype, with dominant and recessive genes working together to make the creatures the way the Creator wants them.
Note: Reginald Crundall Punnet made an important contribution to science when he created the Punnet square – a scientific tool which is nothing like the foursquare game that it resembles, but might be just as fun. It is used to predict the features of a creature that has been crossbred, such as two different kinds of peas or a Labradoodle. Check them out online and have fun!