Next Generation Science Standards

Performance Expectation

Ask questions to clarify relationships about the role of DNA and chromosomes in coding the instructions for characteristic traits passed from parents to offspring.

• Assessment Boundary: Assessment does not include the phases of meiosis or the biochemical mechanism of specific steps in the process.

This performance expectation broadly addresses gene expression and heredity. While we could lecture at students until we're blue in the face, the point of this performance expectation is to have students do the dirty work themselves. They should ask questions that peel back layers of the onion in order to get to the delicious, Tootsie-roll center of DNA, genetics, and heredity. (How's that for switching horses in midstream of a metaphor?)

Asking questions to clarify means that students already understand the role of DNA in heredity—at least in a fuzzy, more-or-less kind of way. As they ask questions and uncover answers, their questions will become more sophisticated, and they'll learn more and more about the specifics of how genes and generations are intertwined. Well, that's the idea, anyway.

To get your students' questions earning top marks, try some of these activity ideas on for size:

• It's research time. Have students ask a question about how DNA relates to heredity and use textbooks, the Internet, and/or their Nobel prize-winning scientist friends (doesn't everyone have a few?) to answer them. Once they find the answer to their question, they can identify what they learned and what they still don't know. They can form a new, more sophisticated question about what they don't know and repeat the process—forever.
• Split the class into teams and, armed with biology textbooks (or a Shmoopy equivalent), ask them a very basic question about DNA and heredity. The fastest team to answer must come up with a new, more specific question. Start each round with a new basic question. The team with the best questions and fastest answers wins.
• Given a handout with a few questions about DNA and heredity, have students arrange the questions in order of depth. After looking up and writing down the answers, they can then come up with more questions that delve deeper into a more specific topic. If they can't find the answer to a particular question, you could even have them write what they think the answer might be. (Do we smell a hypothesis?)
• Stressing out over teaching about gene regulation? Use the stress response system as an example of a heritable trait linking genotype to phenotype. When a student is freaking out over that gnarly world history test, their upcoming lead role in Footloose, or a rabid charging rhino, the stress hormone cortisol is released and binds its cytoplasmic receptor. Now a transcription factor, this complex turns on and off many genes so the student acts appropriately (i.e., runs) in the face of danger. Ask small groups of students to write down questions that address why some people run away and others stay and fight.

Disciplinary Core Ideas

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. (Secondary to HS-LS3-1) (Note: This Disciplinary Core Idea is also addressed by HS-LS1-1.)

Okay, back to basics. You've probably heard the analogy that DNA is the blueprint of life. We like to think of it as the instructions in a set of LEGOs. Step by step, you're shown what blocks (specific amino acids) to place precisely together to form that T-Rex, Death Star, or Frozen ice castle.

Make sure students understand the basic gist here, otherwise they won't be able to ask themselves very good questions. There are some seriously sweet animations online (check out the WEHImovies YouTube channel for some good ones) to help visualize DNA and the process of making proteins from genes.

LS3.A – Inheritance of Traits: Each chromosome consists of a single very long DNA molecule, and each gene on the chromosome is a particular segment of that DNA. The instructions for forming species' characteristics are carried in DNA. All cells in an organism have the same genetic content, but the genes used (expressed) by the cell may be regulated in different ways. Not all DNA codes for a protein; some segments of DNA are involved in regulatory or structural functions, and some have no as-yet known function.

There's a lot going on in this disciplinary core idea, but remember, you don't have to do all the heavy lifting; if students explore and ask questions themselves, you can save that 300-slide PowerPoint presentation in case you ever have to filibuster.

Students should primarily come away with an understanding of 1) the composition, structure, and organization of the genome; 2) transcription, translation, and the many roles of proteins (including ones we don't know yet); and 3) that proteins in sum make up our traits, which can be heritable.

That means they'll need to understand genotype, phenotype, mitosis, differential gene expression, and sexual reproduction (giggity giggity!). Although the general purpose and result of meiosis should be covered, students don't need to memorize its specific stages or mechanisms. (See you never, Anaphase II!)

One last thing: the NGSS says that all cells within an organism have the same "genetic content." By content, they mean that the sequence of base pairs in a DNA strand is the same in all cells. They're not talking about the amount of DNA in a cell, because otherwise we couldn't have things like gametes.

Science and Engineering Practices

Asking Questions and Defining Problems: Ask questions that arise from examining models or a theory to clarify relationships.

Students who master this skill in the context of this performance expectation use their understanding of the basic theories of gene expression and heredity to come up with thoughtful, focused questions that identify the relationship between genotype and phenotype at multiple levels of examination. Got all that?

In other words, why is asking good questions important? When students identify what they already know and acknowledge what they don't, they can ask questions and form hypotheses to explore what they don't know. And really, that's what science is built on.

Crosscutting Concepts

Cause and Effect: Empirical evidence is required to differentiate between cause and correlation and make claims about specific causes and effects.

Scientists design experiments in certain ways in order to understand the relationships between particular events. That means distinguishing between evidence indicating correlation (one thing happens along with another) and causation (one thing leads to another). And as we all know, correlation doesn't imply causation.

Of course, in order to come to their own conclusions about whether things are correlated or causal, students will need empirical evidence from an experiment—the real, raw data, straight from the source. We don't want the evidence filtered through someone else's eyes—unless it's the original scientists who did the study, of course.

Teaching students the importance of credibility (read: avoiding Yahoo! Answers) and how to evaluate and cite information they find online will also help with this performance expectation (and many, many others).