Heritable Characteristics & Diseases

Instructor: Ebony Potts

Ebony has taught middle and high school physical science, life science & biology. She's also been an assistant principal and has a doctorate in educational administration.

Have you ever wondered how traits are passed on from one generation to the next? In this lesson we will discuss this process, as well as some specific traits and diseases that can be passed from parent to offspring.

All in the Family

Have you ever been to a large family gathering before? If you have, you probably noticed that many of the people at the gathering looked alike. If you spent time with some of those individuals, you may have also noticed that some of their behaviors were similar as well. You may have noticed that many in the family have brown eyes and dark tightly coiled hair. If you observed another family, you may have noticed that many of those family members have very straight hair and narrow eyes. No matter what family you observe, be it a human family or any other group of related organisms, you will observe similar traits among them.

How Traits Are Inherited

All living things have certain characteristics that they have in common. These shared characteristics is what makes them living things. One of the hallmark characteristics that separates living and non-living things is the ability to reproduce. The objective of reproduction is to create an offspring that usually ends up with similar traits as its parent(s). But just how are these traits passed on from parents to offspring?

The study of how traits are passed from parent to offspring is called genetics. Any genetics book would tell you that inherited traits are passed from parents to offspring on genes that are a part of their DNA. DNA, or deoxyribonucleic acid, is a long chain of phosphorus, lipids, and other chemicals, that when read and expressed gives an organism the characteristics that make it what it is. Your mom is who she is because of the information that is contained in her DNA. The same goes for your cat, as well as the tomato you ate for lunch. Each organism contains something like a recipe book to make them who and what they are. The recipe is different for each species and organism, and the recipe is contained in DNA.

As we said previously, traits are passed and expressed through the genes that are a part of DNA. A gene is a portion of DNA that, when expressed, codes for a specific protein to be produced. Those proteins are what control our traits. It sounds very complicated - and it is - but an easy way to think of genes is that they are like chapters in the DNA recipe book. Each chapter is for a different trait. Chapter 10,025 may cover eye color, and chapter 3,001 might cover height.

Each parent produces sex cells (egg or sperm) that contain half of their DNA, or half of their recipe book. When the two sex cells unite a new set of DNA is created, a new chapter book with some of the genes or chapters from both parents. So the offspring ends up with traits from both parents and both families. That's why your little cousin Donovan may have his dad's ears but his mom's thick hair.


What Can and Cannot Be Inherited?

Now that we have explained that traits are inherited when parents pass genes to their offspring via DNA contained in their sex cells, let's discuss what can be passed on via DNA. We have already discussed some examples like eye color, height, and hair texture, but there are thousands of others. Basically, any trait that can be directly linked to what is contained in your DNA is a heritable trait. Even some diseases are heritable. Heritable diseases are often called genetic disorders. A genetic disorder is a condition caused by damaged, incomplete, or incorrect DNA passed from parent to offspring. Some examples of heritable diseases or genetic disorders include Down syndrome (causes a characteristic appearance and learning difficulties), achondroplasia (dwarfism), and sickle cell anemia (causes sickle shaped blood cells and pain crisis).

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