SPEAK OUR LANGUAGE

• CELL – Core Experience Learning Lab
• SDR – Scientist Data Record

ASK WHY

Great scientists question the world around them. We encourage our LabLearner students to do the same. In anticipation of this, we explain the importance of learning the concepts in the Ask Why section within the CELL. Our hope is that these explanations help students understand why science matters.

BRANCH OUT

Each Investigation introduces students to a different branch of science or STEM (Science, Technology, Engineering, Mathematics) career that utilizes the scientific concepts of the CELL. These real-world connections will help students see the relevance of what they are learning. STEM connections are also integrated into each Performance Assessment.

GET FOCUSED

The Focus Questions in each Investigation are designed to help teachers and students focus on the important concepts. By the end of the CELL, students should be able to answer the following questions:

Investigation 1:

• How does DNA control the functions of an organism? Genes contain DNA sequences that encode for proteins. Proteins are responsible for most of the functions of an organism’s cells.

• Can mutations in DNA cause changes in an organism? Mutations may or may not lead to changes in an organism.

Investigation 2:

• Can mutations in DNA cause changes in an organism? Yes, however not all mutations cause changes in an organism.

Investigation 3:

• Why can mutations in the DNA of a single cell affect the functions of an entire organism? A mutation of the DNA in a gene in a single body cell will get copied when the chromosomes duplicate. All of the new body cells formed through mitosis will then have the mutation. If the mutation causes a change in a protein, all cells will produce the mutant protein. If the cells in an organ are producing mutant proteins, the organ may not function properly. Thus the organism may not function properly.

Note: These are succinct responses to the Focus Questions and are placed here for easy reference. Fully developed responses to the Focus Questions can be found on each PostLab page.

Note: Some questions may be revisited as the CELL progresses. As students acquire additional knowledge, their responses should reflect this.

LEARN THE LabLearner LINGO

The following list includes Key Terms that are introduced within the CELL. These terms should be used, as appropriate, by teachers and students during everyday classroom discourse.

Note: Additional words may be bolded within the Backgrounds. These words are not Key Terms and are strictly emphasized for exposure at this time.

Investigation 1:

• DNA: nucleic acid that carries genetic information in cells and consists of two complementary chains of nucleotides wound in a double helix
• Protein: large molecule consisting of one or more chains of amino acids (polypeptides)
• Amino Acid: building block of protein molecules
• RNA: group of single-stranded nucleic acids, including mRNA (messenger RNA) that is necessary for transcription and translation
• Codon: three adjacent nucleotides in DNA or mRNA that code for a specific amino acid in a protein
• Mutation: a change in the DNA sequence of a gene

Investigation 2:

• There are no Key Terms introduced in Investigation 2.

Investigation 3:

• Chromosome: structures of DNA and protein in the nucleus of cells, where genes are located
• Mitosis: nuclear division characterized by chromosome replication and formation of two identical daughter nuclei

BE PREPARED

An overview of the materials for each lab is placed here for easy reference. Specific teacher preparation for the labs is placed at the beginning of each Lab page.

EXTEND YOUR THINKING

The following information is included so that teachers have additional background knowledge pertaining to the concepts introduced in the CELL. Teachers may choose to use this information enrich students during instruction, but this is optional and not necessary for the intended students’ learning outcomes.

There are four main types of biological molecules: carbohydrates, proteins, nucleic acids, and lipids. This Core Experience Learning Lab concentrates on two of these – proteins and nucleic acids. Nucleic acids and proteins are both organic molecules. Both are also polymers. A polymer is a long, chain-like molecule of similar or identical repeating units called monomers.

Proteins are polymers of amino acids or polypeptides. Proteins are very large biological molecules that control almost all functions of a cell. Proteins provide structure, catalyze chemical reactions, transport materials, regulate functions, and act as signals.

Nucleic acids are polymers of nucleotide. A nucleotide consists of a phosphate group, a pentose (5 carbon) sugar, and a nitrogenous base. Nucleic acids differ from each other in the type of sugar and the types of nitrogenous bases that they contain. There are two types of nucleic acids, DNA and RNA.

Deoxyribonucleic acid (DNA) contains nucleotides that consist of the sugar deoxyribose. The four nitrogenous bases found in DNA are the pyrimidines, cytosine and thymine, and the purines, adenine and guanine. DNA is a double-stranded nucleic acid consisting of two nucleotide strands. These strands form a double helix with the sugar phosphate backbones on the outside and nitrogenous base pairs on the inside. The helix is held together by hydrogen bonds and van der Waals forces between base pairs.

The two strands of DNA are complementary. Because of the molecular structure of the bases, adenine always pairs with thymine and cytosine always pairs with guanine. Because the strands are complementary to each other, the strands can serve as templates for each other. This characteristic of DNA makes replication, the process by which copies of DNA are made, possible.

DNA is often called the genetic material of the cell. Genes are made of DNA. Each gene encodes for one protein. However, genes do not make proteins directly. DNA is located in the nucleus of eukaryotic cells, but protein synthesis occurs in the cytoplasm on structures called ribosomes. The transfer of information from DNA in the nucleus to the ribosomes is mediated by RNA.

Ribonucleic acid (RNA) is made up of nucleotides that contain ribose as the sugar. RNA contains three of the same nitrogenous bases as DNA – cytosine, adenine, and guanine. The fourth base in RNA is the pyrimidine uracil. RNA does not contain thymine. RNA is singlestranded, consisting of only one polynucleotide chain.

There are many types of RNA in cells, and they serve many different functions. Some of the major functions of RNA are involved in protein synthesis. The three major types of RNA that are involved in protein production are mRNA (messenger RNA), tRNA (transfer RNA), and rRNA (ribosomal RNA).

The transfer of information from genes to RNA to protein occurs in two steps, as shown in Figure 1. The first step is transcription. In this step the information in DNA is transferred to RNA. The second step is translation. In this process, the information in RNA is translated into a polypeptide (protein).

During transcription, RNA is formed by a protein called RNA polymerase. The polymerase uses one strand of DNA as a template for the RNA. The strand of mRNA is complementary to the template DNA strand. For example, the base guanine in the DNA template would correspond to a cytosine in the RNA transcript. This is illustrated in Figure 2. Transcription occurs in the nucleus of the cells. In eukaryotic cells the RNA transcript is called pre-mRNA. Additional processing occurs in the nucleus to remove non-coding regions of the pre-mRNA and splice together the coding regions to form mRNA.

The mRNA leaves the nucleus and is transported to a ribosome in the cytoplasm. Translation occurs on ribosomes. Translation is the is the RNA-directed synthesis of polypeptides. During translation, the mRNA is “read” as a series of three bases called codons, as shown in Figure 2. Each codon encodes for a specific amino acid. There is some built in redundancy in the system, as some amino acids have more than one codon. There are also start and stop codons that initiate and signal the end of polypeptide synthesis.

After translation, the polypeptide chain will fold to form its final structure. There are four levels of protein structure. The first level, primary structure, is simply the chain of amino acids. Hydrogen bonding between amino acids in the protein causes the formation of secondary structures – helices and pleated sheets. Additional folding due to side-chain interactions forms a precise conformation called tertiary structure. All proteins have these first three levels of structure. Some proteins consist of two or more folded polypeptides called subunits that aggregate together. This is called quaternary structure. The proper folding of a protein into its unique structure is essential to its function.