Next Generation Science Standards

Performance Expectation

Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.

• Assessment Boundary: Assessment does not include identification of specific cell or tissue types, whole body systems, specific protein structures and functions, or the biochemistry of protein synthesis.

Even Nana Shmoop knows a DNA strand is shaped like a double helix. What she doesn't know is that the shape is due to its special chemical composition: a backbone of sugars and phosphates linked to bases, the order of which literally determines what proteins our cells make. Nana: "Protein…like, chicken?" Now we have some explaining to do.

Your students likely already know way more than Nana Shmoop when it comes to DNA, which is good, because the point of this performance expectation is for them to construct an explanation for how DNA is the blueprint for making proteins. If they're just starting to learn about DNA or simply need a review, try some of the beginning activity ideas below on for size. If they're already DNA champions, they can dive in and gather evidence from the internet, textbooks, or any grandmas who used to work in molecular biology labs.

It's a downward DNA spiral, but in a good way, with these activity ideas:

• Break the class up into expert groups. Have one group research and come up with a short presentation on the structure of DNA, including base-pairing laws, but not replication. Put another group in charge of transcription, one in charge of RNA processing, and then one in charge of translation. Once they're all ready, have them give their presentations to the rest of the class in that same order because…well, that's the central dogma.
• Turn your students into code breakers. First, have them each write out three separate sequences of 5–7 common amino acids to create super basic (albeit imaginary) proteins. Then, on a separate sheet of paper, have them write out what codons (i.e. RNA base pairs) would code for those proteins. Remind them they need to include start codons and stop codons for each protein. Next, have them partner up and swap their RNA base sequences and then decode each other's sequences to determine the correct proteins they form. Of course, they'll need a RNA base decoder chart, so feel free to send them to this nifty one from our Shmoop learning guide.
• Put students into small groups and challenge them with this question: "If DNA has our entire genetic code in it, and every cell has DNA in it, then how does our liver know to only make liver proteins, or our skin to make only skin proteins?" Have them discuss, and then let them hop online to delve into the world of gene expression. They'll then need to report their findings back with a poster, diagram, or some other variety of visual representation of how gene expression works.

Disciplinary Core Ideas

LS1.A – Structure and Function: Systems of specialized cells within organisms help them perform the essential functions of life.

Although students don't need to know specific cell or tissue types, whole body systems, specific protein structures and functions, or the biochemistry of protein synthesis for this performance expectation, it's important that they understand that many types of cells work together in tissues to create the bustling community that is the organism. If all of our cells contained the same proteins, we would probably be stinky blobs, quickly dissolving into puddles of goop without the help of a specialized immune system.

Luckily for us, organisms evolved compartments—tissues and organs—that work together on several levels—cellular, tissue, organ, and systemic—to increase their complexity so they can grow, interact with their environments, adapt, and reproduce. Once students know that, it's a logical next step to see that something must decide what types of proteins get made in the body. That something, of course, is DNA.

LS1.A – Structure and Function: All cells contain genetic information in the form of DNA molecules. Genes are regions in the DNA that contain the instructions that code for the formation of proteins, which carry out most of the work of cells. (Note: This Disciplinary Core Idea is also addressed by HS-LS3-1.)

We like to think of DNA as the instructions in a LEGO set. Step by step, you procure different blocks and place them precisely together to form that T-Rex, Death Star, or Frozen ice castle. LEGO blocks are like specific amino acids that, when combined, make up a protein and determine its traits. Each step in the instructions (gene) tells you which color and type of block (amino acid) to find and where/when to connect them with others blocks. You can try asking your students to make an analogy between parts of LEGO set (including the instructions) and gene expression. Everybody loves LEGOs.

There are also some seriously sweet animations online to help visualize DNA and the process of making proteins from genes. Some of our favorites show realistic depictions of DNA organization, transcription , and translation. There's no narration in the last two videos, just weird bubbly noises; is that what being inside a cell sounds like? You can use this as an opportunity to ask students questions during the video and have them write down their own questions.

Science and Engineering Practices

Constructing Explanations and Designing Solutions: Construct an explanation based on valid and reliable evidence obtained from a variety of sources (including students' own investigations, models, theories, simulations, peer review) and the assumption that theories and laws that describe the natural world operate today as they did in the past and will continue to do so in the future.

What counts as reliable evidence in the context of this performance expectation? To satisfy this performance expectation, students may read about theories solidified from extensive experimentation, unsubstantiated claims, papers with data, and explanations in textbooks. How will they know what constitutes evidence good enough to construct a claim? A classroom discussion on this article or short writing assignment can help clarify what types of information count as good evidence.

Once students have their evidence in hand and analyze it, they can write papers, give oral presentations, make posters, videos, or whatever else you want them to do to describe their assertions. These can include reasons why they trusted the resources they used, and should also showcase an understanding that DNA has been the blueprint of life for millions of years, and will continue to do so for millions more, or at least until we evolve into some sort ethereal super creatures that don't need proteins any more.

Crosscutting Concepts

Structure and Function: Investigating or designing new systems or structures requires a detailed examination of the properties of different materials, the structures of different components, and connections of components to reveal its function and/or solve a problem.

Let's say we have a time machine and are able to pluck young Thomas Edison out of his easy chair and drop him into the driver seat of a Volkswagen Beetle. Since he's a smart dude, he'd probably figure out how to drive it, but without taking a look under the hood, he might think the horseless buggy runs on magic. Finally, he manages to figure out how to pop the hood, and begins his investigation to figure out how this chariot runs. Scientifically, he begins by analyzing each part's material properties and structural design. Once he understands this, he examines how the parts fit together as a whole. It might take him weeks or months, but his fine dissection of the punch buggy eventually leads to his understanding of how it works.

The concept that an understanding of how something works requires detailed examination applies to many fields, biology included. In the context of this performance expectation, students can learn how the structure of DNA determines the structure of proteins and their functions by zooming into their molecular makeup; structure and function emerge from these basic properties. We might not all be Thomas Edisons, but with the right training and a heavy dash of perseverance, we have the potential to solve super difficult design problems.