Biology 12

SKILL FOCUS

Predicting

Planning and initiating

Performing and recording

Communicating results

Conducting research

Investigation

DESIGN YOUR OWN

8•A

Problem

How can you use materials available in your home or

classroom to simulate the process of transcription and

translation?

Prediction

Predict which aspects of protein synthesis will be

relatively easy to simulate in the classroom, and which

will be more difficult.

Materials

Select your own materials as determined by your

experimental plan.

Experimental Plan

1.Working in a group, make a list of the steps involved

in transcription and translation. Prepare a second

list that includes the main structures, molecules,

and processes involved at each step.

2.Discuss with your group how you might simulate

the processes of transcription and translation in the

classroom. Some possibilities include

assigning different locations in the classroom to

different cellular structures, and the actions of

different molecules to various students to role

play; or

developing models using paper cutouts or other

materials.

Simulating Protein Synthesis

Throughout the 1950s and 1960s, scientists developed a number of models to

explain the steps in protein synthesis even though they were not able to see most

of the processes taking place at the cellular level. Today’s researchers can now

use electron microscopy to help them see and analyze molecular processes,

but large-scale models are still an important tool in scientific research. In this

investigation, you will work with a team to develop and present a simulation of

protein synthesis.

moving a distance of exactly one mRNA codon in

the 5 ′– 3 ′direction, is called translocation.

Translocation brings the tRNA holding the

polypeptide chain into the P site, and exposes a new

A site for attachment by a new tRNA molecule. The

tRNA molecule that was in the P site is now in the

E or exit site, and it detaches from the ribosome.

This released tRNA molecule will bind with a new

amino acid to continue the process. Altogether, the

three steps of the polypeptide elongation cycle, as

shown in Figure 8.19 at the top of the next page,

take a total of about 0.10 s to complete.

Termination

The elongation cycle continues until a stop codon

appears on the mRNA strand in the A binding site.

Termination occurs when this codon is reached

because there is no tRNA with the complementary

anticodon. The previous tRNA, carrying the

completed polypeptide chain, remains in the P site

As you research the topic you have chosen for your

Biology Course Challenge, consider how it relates to

gene expression. Here are some ideas.

• If you are studying a disease or disorder, research
  how changes in gene expression can contribute to this
  condition. How do these changes arise at the molecular
  level?


• Create a list or flowchart of some of the ways in which
  interactions among DNA and proteins within cells
  can affect people and, more broadly, society and the
  environment. Use your results to help further your work.

COURSE CHALLENGE

To view an animation clip on tRNA and translation, consult

your Electronic Learning Partner.

ELECTRONIC LEARNING PARTNER

266 MHR • Unit 3 Molecular Genetics