Chapter 1: Understanding DNA

DNA, or deoxyribonucleic acid, is a remarkable molecule capable of replication, serving as the foundation of all life on our planet. This means that, in a surprising twist, humans share a genetic link with bananas. Welcome to the 25th installment in our series on Earth’s history.

Filling the Historical Gap

In the vast timeline of Earth, we find ourselves 2.3 billion years ago during the Huronian Glaciation. With not much action happening on our planet, it’s the perfect moment to delve into the significant topic of DNA.

Every living organism shares a common thread, and you can even transfer a gene from a human to a fruit fly, with effective results. This is possible because humans and fruit flies share approximately 60% of their genetic makeup. Interestingly, the same percentage applies to us in comparison to certain fruits, such as bananas. As Bill Bryson eloquently notes, "Every living thing is an elaboration on a single original plan," and at the core of that plan lies DNA.

What Constitutes DNA?

At its essence, DNA is a molecule composed of carbon, nitrogen, oxygen, phosphorus, and hydrogen. It has been present since at least the time of LUCA (the Last Universal Common Ancestor) and is found in nearly every cell of living organisms. To put this into perspective, humans possess DNA in each of our 30 trillion cells (excluding red blood cells). Each cell contains about 2 meters of DNA, leading to a staggering estimate of at least 20 billion kilometers of DNA per individual.

Now that’s impressive! 🌟

The Structure of DNA

For a bit of creativity, imagine constructing DNA using LEGO, Velcro, and wire. Gather some standard imaginary 2x4 LEGO blocks in four colors: blue, white, red, and black. Attach Velcro to one end of each block and connect them end-to-end with the Velcro facing each other. It's crucial to pair blue with white and red with black, although the sequence can be reversed.

If you're simulating bacterial DNA, repeat this step about 4 million times; for human DNA, aim for around 3 billion repetitions. Attach a long wire to each end of the LEGO pairs, forming a long rope ladder, and twist it to create two intertwined spirals. Congratulations! You've made a rudimentary model of bacterial DNA.

The Role of DNA

How does DNA function? The rungs of the DNA ladder work in teams, forming genes, which can number between 500 and 7,500 in bacteria. Each gene is responsible for producing specific proteins, and collectively, they make up an organism's genome. Thus, DNA acts as the governing authority for biological entities, directing all bodily functions through its instructions. However, DNA is primarily a manager, delegating tasks to proteins, much like a board of directors overseeing a company without engaging in daily operations.

The Process of Replication

DNA has a remarkable ability to replicate itself. In humans, billions of new cells are generated daily. During this process, the DNA molecule splits down the middle, unfastening at the Velcro connections. The cell then duplicates the other half to create new DNA, ensuring that red is always paired with black and blue with white. This replication is typically straightforward, allowing one cell to become two.

This is how multicellular organisms grow and single-celled organisms reproduce. While this process is usually flawless, occasional errors can occur, which will be explored in Part 26.

This article marks the 25th in a series of 50, each highlighting a 100-million-year segment in Earth’s history.

How Did Life on Earth Begin?

In this video, we explore the origins of life on our planet, delving into scientific perspectives and theories.

Where is the Origin of Life on Earth?

This video investigates various hypotheses about where life first emerged on Earth, shedding light on the intriguing possibilities.

For those interested in further reading, check out Part 24: GLACIATION or stay tuned for Part 26: EVOLUTION. If you'd like to explore the entire series, feel free to follow along!