Farming is a great way to learn about nature, biology, engineering, and so many other parts of life. Recently, someone asked me about a cow that had twin calves. One calf was black with a white head, and the other was red with a white head. Both the bull and the cow had black bodies, and the cow had a white head. The big question was: How can two black animals have a red calf?

The answer comes from the work of a German monk named Gregor Mendel. In 1866, he published findings that became the foundation of modern genetics. He experimented with honeybees, mice, hawkweed, and especially pea plants. His pea research is what made him famous, though his work was largely overlooked until it was rediscovered after his death.

Mendel is credited with several key ideas. He developed the concept of dominant and recessive traits. He didn’t know about DNA or genes (that discovery came much later, in 1953, with James Watson and Francis Crick), but he figured out how traits are passed from parents to offspring. He showed how some traits can skip a generation and then reappear in very specific ratios.

He also worked out the ideas we now call genotype (the genetic makeup) and phenotype (the physical appearance), even though he used different words for them. We still use letters today to represent traits: capital letters for dominant traits and lowercase letters for recessive ones.

Using this system, we can map out the genetics of animals and see what combinations of genes the parents pass on to their calves. This is the key to understanding inheritance.

Cattle coat color is more complicated than just black and red, but we’ll keep it simple for this example. For a deeper dive, check out this excellent article by Megan Rolf from Oklahoma State University Extension: Color Patterns in Crossbred Beef Cattle.

Let’s treat coat color as controlled by one gene with two versions:

● B = black coat (dominant)

● b = red coat (recessive)

Every animal has two copies of the gene—one from the mother and one from the father.

● BB = black coat

● Bb or bB = black coat (black is dominant, so the red version is hidden)

● bb = red coat (needs two recessive genes)

Now back to our example. The black cow and black bull had one black calf and one red calf. For a red calf to appear, it must have two recessive genes (bb). That means both parents had to carry one hidden red gene. In our letter system, both parents were Bb (heterozygous black).

Each parent can pass on either a B or a b gene. Here’s how the possible combinations work out:

● BB → black calf (25% chance)

● Bb or bB → black calf that carries red (50% chance)

● bb → red calf (25% chance)

This explains exactly what happened with the twins. The red calf received the recessive “b” gene from both parents. The black calf received at least one dominant “B” gene.

Genetics and inheritance are fascinating topics. Today, with advances in science, we can look deeper into the genomics of animals to see not only what traits they show, but what hidden genes they carry.

If you have questions about agriculture, horticulture, or livestock, we’d love to hear from you. Call the Caldwell County Extension Center at 828-757-1290 or visit us online at caldwell.ces.ncsu.edu.

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NC State Extension's mission is to extend research-based knowledge from NC State University and N.C. A&T State University to all North Carolinians, transforming science into everyday solutions that improve lives, grow the state's economy, and enrich communities. Seth Nagy is the Caldwell County Extension director. The Caldwell County Extension Center is located at 120 Hospital Ave. NE #1 in Lenoir.