Biology (Holt)

Before You Begin

contains the instructions that cells need

in order to make every required to

carry out their activities and to survive. DNA

is made of two strands of

twisted around each other in a.

The two strands are ,that is,

the sequence of bases on one strand deter-

mines the sequence of bases on the other

strand. The two strands are held together by

hydrogen bonds.

In this lab, you will build a model to help

you understand the structure of DNA. You

can also use the DNA model to illustrate and

explore processes such as and

.

1.Write a definition for each boldface term

in the paragraphs above and for each of

the following terms: replication fork, base-

pairing rules.

2.Identify the three different components

of a nucleotide.

3.Identify the four different nitrogen bases

that can be found in DNA nucleotides.

4.Based on the objectives for this lab, write a

question you would like to explore about

DNA structure.

Procedure

PARTA:Design a Model

1.Work with the members of your lab group

to design a model of DNA that uses the

materials listed for this lab. Be sure that

your model has at least 12 nucleotides on

each strand.

2.Write out the plan for building your model.

Have your teacher approve the plan before

you begin building the model.

3. Build the DNA model your group
   designed. CAUTION: Sharp or
   pointed objects may cause injury. Handle
   pushpins carefully.Sketch and label the
   parts of your DNA model.
   4.Use your model to explore one of the
   questions written for step 4 of Before
   You Begin.

You Choose

As you design your model, decide the following:

a. what question you will explore

b.how to use the straws, pushpins, and paper

clips to represent the three components of

a nucleotide

c. how to link (bond) the nucleotides together

d.in what order you will place the nucleotides

mutation on each strand

replication

complementary

double helix

nucleotides

protein

DNA

Exploration Lab

Modeling DNA Structure

SKILLS

• Modeling


• Using scientific methods

OBJECTIVES

• Designand analyze a model
  of DNA.


• Describehow replication
  occurs.


• Predictthe effect of errors
  during replication.

204 CHAPTER 9DNA: The Genetic Material

MATERIALS

• plastic soda straws,
  3 cm sections


• metric ruler


• pushpins (red, blue,
  yellow, and green)


• paper clips

2A 3E 6A 6B 6E