Have you ever looked in the mirror and thought, “Wow, I look just like my mom, but I laugh exactly like my dad”? Or wondered why some people are lactose intolerant or have attached earlobes? That’s genetics in action.

Genetics is the science of how traits are passed from one generation to the next, and it explains everything from eye color to inherited diseases to whether or not you think cilantro tastes like soap.

What Is Genetics?

Genetics is the study of heredity, or how traits are inherited from parents. It all starts with DNA, a molecule made of a code written in four letters: A, T, C, and G. These letters form instructions called genes, which are passed down from your parents.

From DNA to Traits

Let’s break it down:

• DNA = the long code in your cells
• Genes = short stretches of DNA that control specific traits (like blood type)
• Chromosomes = bundles of genes (you get 23 from mom, 23 from dad)
• Proteins = made using gene instructions and do most of the work in your body
• Traits = the visible result (like blue eyes or curly hair)

You inherit two copies of each gene, one from each parent.

Meet Gregor Mendel: The Pea Plant Legend

Gregor Mendel was a 19th-century monk who basically invented genetics by studying pea plants. He figured out that traits are inherited in predictable ways, some traits dominate over others.

He discovered:

• Traits are passed down through “units” (we now call these genes)
• Some traits are dominant (they show up if even one copy is present)
• Some are recessive (they only show if both copies are recessive)

Thanks to Mendel’s work, we can predict how traits might appear using a simple tool…

How to Make a Punnett Square

A Punnett square is a diagram used to show all the possible combinations of gene pairs that can result from a genetic cross.

Let’s say B = brown eyes (dominant) and b = blue eyes (recessive):

	B	b
B	BB	Bb
b	Bb	bb

This shows:

• 25% chance of BB (brown)
• 50% chance of Bb (still brown)
• 25% chance of bb (blue)

Steps to make your own Punnett Square:

1. Write one parent’s alleles across the top.
2. Write the other parent’s alleles down the side.
3. Fill in each box with a combination.
4. Analyze the outcomes.

Easy genetics math!

Beyond Simple Dominance

Not all traits follow Mendel’s neat dominant/recessive rules. Let’s look at some non-Mendelian inheritance patterns:

Incomplete (Partial) Dominance

Neither allele is fully dominant. The result is a blend.

• Example: red (RR) + white (WW) = pink (RW) flowers.

Codominance

Both alleles are fully expressed.

• Example: A and B blood types → AB blood. Both show up, not blended.

Multiple Alleles

Some traits are controlled by more than two alleles.

• Example: Blood types (A, B, O). You inherit two, but there are three options.

Polygenic Traits

Traits controlled by many genes.

• Example: height, skin color, intelligence. These traits have a range, not just “tall” or “short.”

Sex-Linked Traits

Traits located on the X or Y chromosomes. Since males have only one X, they’re more likely to express recessive X-linked traits like color blindness or hemophilia.

Genotype vs. Phenotype

• Genotype = your actual gene pair (BB, Bb, or bb)
• Phenotype = the physical expression (brown or blue eyes)

You can have the same phenotype (brown eyes) with different genotypes (BB or Bb).

Why Genetics Matters

• Helps predict inheritance patterns
• Explains family traits and diseases
• Guides research into cures and treatments
• Connects us to every living thing on Earth

Genetics reveals the blueprint of life, and it’s beautifully complex. Whether your eyes are hazel, your hair is curly, or you love spicy food, your genes are the reason. But remember, they’re not the whole story. Environment, choices, and faith shape you too.

You are more than your genes, but your genes are still pretty awesome.