Question Video: Describing How Scientists Use the Genetic Analysis of DNA to Classify Organisms

Which of the following is an assumption scientists make when classifying organisms based on genetic analysis? [A] The more DNA two organisms have in common, the more recently they shared a common ancestor. [B] The more DNA two organisms have in common, the less recently they shared a common ancestor. [C] Organisms have only shared a common ancestor if they have identical DNA.

02:19

Video Transcript

Which of the following is an assumption scientists make when classifying organisms based on genetic analysis? (A) The more DNA two organisms have in common, the more recently they shared a common ancestor. (B) The more DNA two organisms have in common, the less recently they shared a common ancestor. Or (C) organisms have only shared a common ancestor if they have identical DNA.

In order to answer this question, we first have to understand that when we classify organisms based on genetic analysis, we’re grouping them together based on similarities in their DNA or genes. Organisms that are more closely related will have more DNA in common. Since you and your siblings share a more recent common ancestor, your parents, you’ll have more DNA in common than you would have with your less closely related cousins, who share a less recent common ancestor, your grandparents.

The same is true when we talk about classifying organisms. The more recent the common ancestor, the more DNA two organisms will have in common. Let’s look at an example. Cats, humans, and gorillas are all members of the same class, which is mammals. However, humans and gorillas share a more recent common ancestor than the one that they share with cats. Recall our seven taxonomic levels of classification from most general to most specific. They are kingdom, phylum, class, order, family, genus, and species.

When we classify organisms based on genetic analysis, they’ll share a more specific group if they have more DNA in common. Cats, humans, and gorillas all belong to the same class, mammal, whereas humans and gorillas both belong to the same family hominid. They share a more specific classifications because they share a more recent common ancestor and have more genes in common.

Now, we’re ready to answer our question. When classifying organisms based on genetic analysis, scientists must assume that the more DNA two organisms have in common, the more recently they shared a common ancestor.

Nagwa uses cookies to ensure you get the best experience on our website. Learn more about our Privacy Policy.