Authentic Experience Lesson Plan/Laboratory Exercise

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Unit 4, Chapter 13, Section 1:  DNA-the Molecule of Heredity

Biology- The Dynamics of Life, Glencoe, pp. 310-315

Part I:

Anticipatory Set: 

At each table there will be a set of organic chemistry modeling pieces.  On the board will be instructions to play with how these pieces to see how they might fit together to make DNA.

Statement of Objective and Purpose: 

            At the end of this section, the student will be able to:

·        Identify the structure and composition of DNA

·        Describe the process of DNA replication

·        Discuss the importance of DNA to organisms

·        Complete a laboratory exercise in which they extract and examine chromosomes

It is important to understand the structure and function because as we have seen in previous lessons, it is DNA that makes each of unique and is a building block of life.  DNA links all of us together.

Instructional Input:

            The teacher will provide the following input:

A.  Structure and Function:

Describe the structure and function of DNA using overheads making the following points:

·        Hierarchy of the molecule; DNA is a nucleic acid that is made of smaller subunits called nucleotides.

·        Nucleotides are made up of deoxyribose, which is a simple sugar, a phosphate group and a nitrogenous base.

·        A nitrogenous base is an organic ring structure containing one or more atoms of N.

·        Four possible nitrogen bases which differentiate between four nucleotides- adenine, guanine, cytosine, and tyrosine.

·        In DNA nucleotides combine to form two long chains which produce one large molecule.

·        Each chain of nucleotides is made up of individual nucleotides connected to each other

·        Two chains connected by hydrogen bonds between bases so you get a twisted ladder that is like a spring- therefore a double helix.

·        All livings organisms contain DNA made up of the same four nucleotides making up their genetic material.  Question-  How can we be all be different if we are made of the same stuff.

·        Because the order of the nucleotides is arranged different

·        Therefore it is the arrangement or sequencing of nucleotides that forms the genetic information for each individual

Modeling:  With two students help, do minilab on physical shape of DNA

B.     Replication of DNA

·        As we have learned genetic material is passed on from one cell to the next during mitosis and to gametes during meiosis.  This process is called DNA replication

·        DNA replication occurs so that as a cell divides it can make a copy of its chromosomes

·        DNA replicates by making a complimentary copy of itself with adenine pairing up with tyrosine and guanine pairing with cytosine.

·        You can predict the sequence of the new strand by constructing one with its opposite nucleic acid

·        An enzyme breaks the hydrogen bonds between the nitrogenous bases holding the molecule together allowing it to unzip

·        Free nucleotides then pair up with their compliment

·        Each strand is a now an exact copy of the original

·        All of the DNA in all of the chromosomes is copied so that there are two sets of genetic material that can be passed on

Checking for Understanding:

The teacher will draw one half of a DNA molecule on the board and have students give answers as to the proper sequence.

Independent Practice:

For homework the students will read section 13.1, answer the following questions from p. 315, define the following terms from p. 310, and read the lab 13-1 on pp. 75-78 of their lab manual in preparation for tomorrow’s lab

1.      Describe the structure of a nucleotide.

2.      How do the nucleotides in DNA pair?

4.      The sequence of bases on one strand of DNA is :  GGCAGTTCATGC.  What would be the sequence of bases on the complementary strand?

5.      Sequence the steps that occur during DNA replication.

Terms:

            Nitrogen base

            Double helix

            Replication

Closing:

Now that we have theoretically examined the structure of DNA, tomorrow we will do a lab activity on chromosome extraction and analysis to gain practical, hands-on knowledge of DNA.

Part II:

Laboratory Exercise:

            Objectives:

            As result of this lab exercise, the student will be able to

·        Extract chromosomes from a fruit fly larva

·        Stain and examine the chromosomes under the microscope

·        Practice their observational and manipulation skills

Instructional Input:

·        As the second part to this lesson, the students will perform the lab activity on pp. 75-78 of their laboratory manual.  See attached handout.

·        The teacher will have already prepared all necessary solutions as well as gather the necessary material as indicated on p.75 of the lab manual

·        The teacher will read the lab aloud with the students, fielding any preliminary questions they may have

·        At each lab table they will find the necessary materials The students will then proceed with the teacher circulating through the groups providing instruction as needed

·        Approximately ten minutes before class ends, the students will be instructed to begin cleaning up and ask any final questions