Instructor’s Name:  Christina Stewart-Jordan

Subject:  Biology I- Genetics

Date:  June 17, 2008

Period:  4th Period

Time: 50 Minutes

Objective(s):

The Student Will:

    1.  Compare the different components and functions of DNA and RNA, as they relate to

    the replication process; (DOK 2, Biology 5.a);

    2.  Summarize the replication process (DOK 2, Biology 5.a).

.

Materials: 

Textbook, 3-ring binder with 5 tabs, pen and/or pencil, loose leaf paper, and colored pencils.  Teacher will provide marsh mellows, whoppers, candied dots, toothpicks and jelly beans for modeling DNA and RNA.

Do Now: 

1.  Define replication in your notes.

2.  Look at yesterday’s “Do Now” and separate each characteristic you wrote down into categories of inherited traits and environmental traits.

3.  When done, write your answers on the board beside your name.

[Add other physical traits not on the board.]

Discuss:  Why do you think this?  Inherited traits are those which are received from parents’ gene pool:  hitch-hiker’s thumb, attached/ unattached earlobe, ability to roll tongue, eye color, height, etc.

-Environmental traits are those which are influenced by the environment, such as your ability to withstand certain temperatures, or similarities you learn from growing up in a certain environment.

(10 minutes)

Set:

What we are going to do today is see from a molecular level how our DNA and RNA make it possible to form our genes, or those inherited traits that we see expressed physically.

Which traits do you think you have that are not being expressed physically?

Do you think that these are inherited traits or environmental traits?

(5 minutes)

Procedure: 

1.  Discuss “Do Now”.

2.  Begin teacher-led discussion (see above Set).

3.  Review the last lesson on the DNA model:

i. The components of DNA- 5 carbon sugar (deoxyribose), phosphate group, and nitrogenous bases (A, T, C, G)

ii.  The components of RNA- 5 carbon sugar (ribose), phosphate group, and nitrogenous bases (A, U- uracil, C, G)

ii.  What is different between the nitrogenous bases of DNA & RNA?  Uracil

4. Activity:  Split the students into groups of two, and explain that they will be constructing DNA and RNA molecules.  Pass out the students’ activities, along with their candied “components” for constructing DNA & RNA models.  Instruct them to follow the directions from Part I of the activity, and answer the questions when done.  [Go over activity together as a group.]

5.  Show video(s) of DNA replication.

6.  a.  DNA Replication: (to be put in their notes)

    i.  Origin of Replication:  Region where DNA denatures into single strands, signaling the

    start of replication at that site.

    ii.  Replication Fork:  “Y” shaped structure, that is created as a result of the DNA    

    unwinding; moves in the direction of the unwinding DNA.

    iii.  DNA helicase: prevents DNA from recoiling by holding it in place, as replication

    occurs.

    iiii.  DNA primase makes the enzyme, RNA primer, which starts replicating the lagging    

    strand, through complementary base pairing.

    b.  Leading strand:  DNA strand being produced in the 5’ to 3’ direction/ same direction

    as the replication fork.

    i.  DNA Polymerase:  Makes DNA on the leading strand, through complementary base

    pairing.

    c.  Lagging strand:  DNA strand being produced in the opposite, 3’ to 5’ direction.

    i.  Okazaki Fragments:  fragments of DNA, created by the lagging strand.

    ii.  DNA ligase:  Joins/ glues the Okazaki fragments together to form complete its

    complementary strand.

• Then, the RNA primer is removed by DNA Polymerase, as it replaces the RNA primers with DNA;

• DNA ligase follows behind DNA Polymerase to glue the strands together, again, completing the lagging strand.

[Why does DNA Polymerase replace the RNA primer & re-glue the lagging strand?]  RNA codes for base pair A-U, instead of A-T, which is found in DNA.

[Which strand do you think has a better chance of error?] lagging strand

7.  Instruct students to complete quiz on second handout, to be turned in for a grade.

8.  Review (See Closure)

(30 minutes)

Closure:

So, DNA is produced by a process called replication, in which RNA primers and DNA Polymerase create new DNA strands through complementary base pairing of unwound DNA.  The newly formed strands are glued together by DNA ligase.  These new DNA strands make up our chromosomes, which have those hereditary traits that we discussed in the “Do Now”.  Tomorrow we will discuss how those genes are expressed, when we talk about the process of transcription.  Class dismissed!

(5 minutes)

Assessment/ Evaluation:

Objectives: 

•  Compare the different components and functions of DNA and RNA, as they relate to the replication process (DOK 2, Biology 5.a).

Informal:  The teacher will listen to students (M) discuss the components of DNA through the construction of the candied DNA models as a group (C).

Formal:  The teacher will collect the students’ group-assessment quizzes, consisting of the students’ group activities and a summary of the replication process, (C) and record the grades in the grade book (D).

• Summarize the replication process  (DOK 2, Biology 5.a).

Informal:  The teacher will listen to students (M) discuss the replication process as a group, while completing their group-assessment quizzes (C).

Formal:  The teacher will collect the students’ group-assessment quizzes, consisting of the students’ group activities and a summary of the replication process, (C) and record the grades in the grade book (D).