Name:                            Robin L. Lewis

Subject:                         Biology I- Genetics (Day 1)

Period:                           2^nd

Approximate Time:       50 minutes

Objective(s):

The Student Will...

1.    Describe the structure of DNA. (MSF Biology I 5a)

2.    Summarize the main features of DNA replication. (MSF Biology I 5a)

Materials:

Textbook, dry erase markers, erasers

Set:

Think about a family member or a close friend.  On a sheet of paper describe at least three characteristics that make you different from that person.  Next describe at least three characteristics that both of you have in common.  Walk around and review responses.  Select students volunteer their responses.  Have students realize that some of the characteristics they are describing are inherited from a parent.  Ask: what do we call inherited information? (genes) Explain that genes are made of DNA.  Say: Today you will describe the structure of DNA and summarize the main features of DNA replication.

Procedures:

1.    Place set on the board.

2.    Begin teacher-led discussion (see set).

3.    Write the word DNA on the board.  Ask: what does DNA stand for. (Deoxyribose Nucleic Acid)

4.    Review students:  What are the 4 types of organic molecules? (Carbohydrates, lipids, proteins, and nucleic acids)  Which group does DNA belong to? (nucleic acid) Can you think of another nucleic acid? (RNA) Review the words polymer and monomer. (polymer-big unit [train] made up of many small units[cart]-monomers)

5.    Ask: What is DNA?

a.    Like a twisted ladder or spiral staircase.  Two strands or double stranded.  Called double helix.

b.    Made up of nucleotides

c.    Draw the structure of DNA.  Explain the three parts of a DNA nucleotide. [sugar, phosphate group, and nitrogen-containing base]

                                         i.    4 Nitrogen bases are paired together to make the DNA.

1.    Purines-2 rings of carbon: adenine and guanine (the big part)

2.    Pyrimidines-1 ring of carbon: cytosine and thymine (the small part)

3.    Purines pair with pyrimidines to make the “steps” of the DNA ladder. Called complementary base pairing. (What does the word complement mean?)

a.    A pairs with T; G pairs with C

b.    Held together by weak hydrogen bonds.

6.    Ask: What do you think would happen if purines could pair with purines and pyrimidines could pair with pyrimidines?

7.    Discuss the contributions of scientists.

a.    There were many people who helped us find out the structure of DNA those people are:

                                         i.    James Watson-made a model of DNA

                                        ii.    Francis Crick- made a model of DNA

                                       iii.    Rosalind Franklin-created x-rays of DNA

                                       iv.    Maurice Wilkins-created x-rays of DNA

8.    Explain DNA replication

a.    Replication- DNA copies itself

b.    Enzyme helicase unwinds DNA by breaking hydrogen bonds.  [What will happen if the hydrogen bonds of DNA are broken?]

c.    Nitrogen bases are exposed and another enzyme DNA polymerase allows free floating nucleotides to bind to the bases.  Once new nucleotides bind to the bases, hydrogen bonds form and create a new chain of DNA.

d.    The DNA strands separate and two identical DNA molecules are formed.  *Important that the molecules are identical or your nose could out of your ear!

9.    Collect papers from Closure.

Closure:

Review.  Have a student draw the structure of DNA on a sheet of paper and label the parts.  Have the students write the base pairing rules.  Have the students summarize DNA replication in their own words.  Then allow students to place their answers on the board.  Say, “Tomorrow we will look at another nucleic acid-RNA and its structure.”

Assessment/Evaluation:

Objectives:

Ø  Describe the structure of DNA. (MSF Biology I 5a)

Ø  Summarize the main features of DNA replication. (MSF Biology I 5a)

a.    Informal

                                         i.    Listen to student response (M) to questions raised throughout the lesson.

b.    Formal

                                         i.    Students will receive a grade (M) for the Closure activity to determine if the students can describe the structure of DNA and summarize the main features of DNA replication (C).  The grade will be recorded in the grade book (D).

 Create your own educational wiki!HelpPublic, not yet premium Privacy Policy RSS