How Genes Are Inherited

My name is Cecile and I’m a PhD student at the University of Utah. My research is a lot like doing DNA detective work! I look for rare changes in genes that could explain why some kids get autoimmune arthritis, which is when the immune system mistakenly attacks the joints and causes swelling and pain. One day, we hope to discover a new treatment that helps kids and adults with autoimmune arthritis feel better sooner and for longer. When I’m not in the lab, I like to paint, go hiking, and hang out with my friends.

In the video above, genes are shown mostly as separate objects—even though in reality some genes are physically connected to each other. That’s because even when genes are connected, they usually behave as separate objects.

A gene is a set of instructions for building a certain type of protein. Usually, genes are arranged end-to-end in structures called chromosomes. A chromosome is a long DNA molecule, made up of thousands to millions of building blocks. Genes are shorter segments of these long DNA molecules. In some living things, there are stretches of DNA between genes. These stretches are called “non-coding DNA,” because they don’t code for proteins. In humans, about 98% of our DNA is non-coding.

Chromosomes are really just convenient packages for data management. Kind of like how a book bundles a bunch of pages together, a chromosome bundles a bunch of genes together. This makes it easier for cells to do things like copy genes and move them around during reproduction.

Asexual reproduction is a way for living things to make genetically identical copies of themselves. Single-celled organisms like bacteria and protists do it by copying their genes and splitting in two, like the video shows. But there are other ways to do it.

Spider plants and strawberries send out long stems called runners that each grow a new plant at their tip. This is just one of the ways plants clone themselves.

Aphids are sap-sucking insects that clone themselves through a process called parthenogenesis. Females in some aphid species give birth to genetically identical daughters who are already pregnant! A single female can make a giant clone army that can take over a plant in a matter of weeks. Other animals reproduce asexually by breaking into pieces or growing a little bud out of their side, which eventually breaks free.

Many living things can reproduce both ways—sexually and asexually. For example, spider plants and strawberries also grow flowers, which they use for sexual reproduction. And most aphid species can also reproduce with a partner. Usually this happens in the fall, and the females then lay eggs that can safely survive the winter.