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Genes and Proteins

Investigation 3 – PreLab

 

 

 

 

 

 

 

Back to Investigation 3

ZERO-IN

Italicized font represents information to be shared orally or physically completed with the students at this time.

The non-italicized font represents additional information included to support the teacher’s understanding of the content being introduced within the CELL.

ASK WHY

Remind students that genes are instructions, which tell your body how to make all the proteins it needs to survive and grow. By identifying each of these proteins, scientists hope to better understand how your body works, and what is happening when it doesn’t work properly. They hope this knowledge will eventually lead to more effective medicines and treatments.

BRANCH OUT

Remind students that plant scientists use gene modification techniques to develop improved crop varieties such as drought-tolerant maize.

GET FOCUSED

Inform students that the Investigation is designed to help them to answer the following Focus Question:

  • 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: This question is located in students’ SDRs at the beginning and end of the Investigation.

Note: This is a succinct response to the Focus Question and is placed here for your reference at this time. Fully developed responses to the Focus Questions can be found on the PostLab page.

GO DEEPER

As a class, read the Background(s) in the Investigation. Have students read the information aloud or silently to themselves. When students have finished, discuss the following concept as a class:

  • DNA is found inside almost all cells in the body.
  • DNA is located in the nucleus of cells in special structures called chromosomes.
  • The DNA of a chromosome contains many genes.
  • Each body cell has two copies of each chromosome in its nucleus. The copies are called homologous chromosomes.
  • In body cells, each chromosome in a homologous chromosome pair came from a different parent (one from the father and one from the mother).
  • Homologous chromosomes contain the same genes, but they are not identical. They may contain different alleles or versions of the genes. 
  • Cells in the body can divide and produce new cells. They do this through a process called the cell cycle.
  • The first part of the cell cycle called interphase. The cells grow larger and all of the chromosomes are duplicated. Each homologous chromosome in a pair is copied. The two identical copies of each chromosome are called sister chromatids. They are attached together by a structure called the centromere.
  • The second part of the cell cycle is called mitosis. The four phases of mitosis are prophase, metaphase, anaphase, and telophase.

Note: These concepts are integrated into the Background(s) and are used to deepen students’ comprehension of the big ideas.

 

LEARN THE LabLearner LINGO

  • chromosome
  • mitosis

Note: Definitions of these terms can be found on the Introduction page to the CELL.

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

SET FOR SUCCESS

Direct students to complete the Ask Why section in their SDRs. Student answers may vary.

  • Why do body cells divide?
  • How do body cells divide?
  • When body cells divide, how do the new cells get the same amount and type of DNA as the original cells?

Note: In addition to the Key Terms above, the following terms will be defined for students in Backgrounds throughout the Investigation: homologous chromosome, allele, sister chromatids, and centromere. If necessary, introduce these vocabulary terms to students before the Investigation begins.

  • Review the following with students:
  • Each cell goes through a cycle with a beginning and an end that repeat. Cells go through this cycle so that they can divide and form two new cells. The central portion of the cell cycle is mitosis during which the chromosomes separate.
  • Before mitosis begins during interphase, each cell has two copies of each chromosome called homologous chromosomes. During interphase, cells grow larger and all the chromosomes are copied (duplicated) resulting in two copies of each.
  • Mitosis begins with the first of four phases. The four phases are: prophase, metaphase, anaphase, and telophase.
  • In prophase, the chromosomes condense into rod-like structures that can be seen under the microscope and the nuclear membrane dissolves.
  • In metaphase, duplicated chromosomes line up with the centromeres on spindle fibers in the center of the cells.
  • In anaphase, the sister chromatids separate and move down the spindle fibers to opposite ends of the cell.
  • In telophase, the chromatids move to the ends of the spindle fibers. The spindle fibers disappear and new nuclear membranes form around each set of chromosomes.
  • The cell next will divide and each new cell will have identical sets of chromosomes in its nucleus.
  • Inform students that in this Investigation they will model the different phases of mitosis. They will also view cells undergoing mitosis under the microscope.
  • Play the video below. Stop to ask students questions or answer students’ questions when necessary. Remind students to follow along with their SDRs and make any notes that they think might be helpful.
  • After the video, direct students to divide into their lab groups to discuss their strategy for the lab. For example, they may assign certain group members to perform specific functions during the lab.

Note: The purpose of the video is to allow students to anticipate the laboratory experience they will soon encounter. Students should leave this PreLab session with a firm idea of what to expect and how to perform in the lab.

Note: Homework is posted below the video.

HOMEWORK

Tell students that they should review the Investigation in preparation for the Lab.