Instructor’s Name:  Christina Stewart-Jordan

Subject:  Biology I- Genetics

Date:  June 16, 2008

Period:  1st Period

Time: 50 Minutes

Objective(s):

The Student Will:

    1. Describe the structure of DNA (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 rubbing alcohol, detergent, meat tenderizer, water and cups needed for experiment.

Do Now:  

Think about a family member or close friend.  Next, on a sheet of paper, list at least three characteristics that make you different from that person.  Then, list at least three things that make you similar to that person.

[Walk around and review responses.]

What do we call inherited information? (genes)  Where do we get the majority of our genes from? (parents)  

Genes are made of DNA!  And today we will be describing the structure of DNA and summarizing its main features.

(10 minutes)

Set:

Hand out designated cups to each student.  Tell the students that they are going to attempt to make a DNA spiral from their cheek cells.  Pour water into each cup and ask the students to swirl the water in their mouths for one minute.  As they are swirling, add detergent water (about 0.25mL) to their cups.  Then, have them carefully replace liquid back into their cups.  Allow them to swirl for one minute, add a pinch of meat tenderizer (enzyme), swirl once more for ten seconds, and allow to sit for at least ten minutes. (Time!)

Why did we add detergent?  (To break the cellular membrane of the cheek cells.)

After ten minutes, add approximately 2 cm of cold alcohol.  Allow to sit for ten minutes without bumping or swirling.  Allow students to see their DNA at the end of class.

(20 minutes)

Procedure:  

1.  Discuss “Do Now”.

2.   I.  Review the last lesson on the four macromolecules:

i.  What were the four types of organic molecules we studied from our last lesson?

a.  carbohydrates- composed of sugars; lipids- composed of fats & waxes; proteins- composed of amino acids; nucleic acids- composed of nucleotides

ii.  Biological importance

carbohydrates- immediate energy source for cells; lipids- long term energy source, as fat; proteins- makes up muscles and tendons; nucleic acids- stores genetic information for cells.

Which group does DNA belong to? (nucleic acids)

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

4. After getting students started on Set, have them put their cups aside, and begin lesson.

5.  Write the word “DNA” on the board, and prompt for its meaning. (deoxyribose nucleic acid)

6.  What does DNA look like?  A twisted ladder or spiral staircase; Double stranded or two strands; called a double helix.  It is composed of nucleotides.

7.  Turn to page 185 to show the three parts of DNA:  sugar, phosphate group, and nitrogen-containing base

    i.  Explain that 4 nitrogen bases pair together to make DNA.  (page 186)

    ii.  Purines- 2 carbon rings:  adenine and guanine; pyrimidines- 1 carbon ring:  

    cytosine & thymine (& uracil for RNA, which will be discussed during replication)

    iii.  Purines pair with pyrimidines to make the “steps” in the DNA ladder through

    complementary base pairing.      

8.  Complementary Base Pairing:

    i.  A pairs with T; G pairs with C

    ii.  Held together by covalent bonds & weak hydrogen bonds

What do you think would happen if purines could pair with purines and pyrimidines with pyrimidines? (mutations)

9.  Contributing Scientists:

    i.  Rosalind Franklin & Maurice Wilkins:  Created x-ray photographs of DNA, indicating

    that DNA has more than one strand of nucleotides.

    ii.  Watson, Crick & Wilkins: In 1962 won the Nobel Prize in Medicine for creating a

    model of DNA, based off Franklin and Wilkins’ work (Franklin passed in 1958 and was

    not recognized).

10.  Review (See Closure)

(10 minutes)

Closure:

Pass out the quizzes.  Allow the students time to answer, and review the answers by having each student write their answers on the board.  Discuss & review.  

Tomorrow, we will be discussing DNA transcription and replication, which means we will also be discussing RNA.  Turn in your papers.  See you tomorrow!  

(10 minutes)

Assessment/ Evaluation:

Objective:  

• Describe the structure of DNA (DOK 2, Biology 5.a).

Informal:  The teacher will listen to students (M) discuss the components of DNA through experimentation (C).

Formal:  The teacher will collect the students’ self-assessment quizzes, summarizing today’s lesson, (C) and record the grades in the grade book (D).