DNA Structure and Replication

1

Title Page

Genetics Unit plan

DNA Structure and Replication

Douglas S Johnson

Grades 10 11 and 12

Duration: 9 days / 4 Block Schedule

Table of Contents

Purpose of the unitp3

Academic Standardsp3

Objectivesp3-4

Interdisciplinary connections p4

Assessmentsp4

Vocabularyp5

Timelinep6

Resourcesp6-7

Technology p7

Lesson Plansp8-13

Differentiationp 13

Critical Thinking Skillsp13

Pre testp 14-18

Post Testp 19-24

Graphsp 24-26

Narrative Statementsp 27-30

Rubric Separate file

Power Points UsedSeparate file

Purpose of the unit

The purpose of this unit is to help students gain a more advanced understanding of DNA structure, the process of replication, and mutation. Because this is a Genetics course there are no standards directly associated with it. I have utilized some of the life science standards to help connect the topics discussed with important biological concepts. The primary areas I will focus on during this unit include an advanced understanding of the chemical structure of DNA, the importance of histones in DNA structure, the process of replication, errors that can occur during replication, and historical figures and experiments that were important in the understanding of DNA structure and replication. To teach this unit I will utilize several different types of instruction including; power points, developing a timeline, developing concept maps, a DNA extraction lab, and a project that involves presenting a concept involved in the chapter to the rest of the class.

Standards

B.1.23Understand that and describe how inserting, deleting, or substituting DNA segments can alter a gene. Recognize that an altered gene may be passed on to every cell that develops from it, and that the resulting features may help, harm, or have little or no effect on the offspring’s success in its environment.

B.1.24Explain that gene mutations can be caused by such things as radiation and chemicals. Understand that when they occur in sex cells, the mutations can be passed on to offspring; if they occur in other cells, they can be passed on to descendant cells only.

B.1.26Demonstrate how the genetic information in DNA molecules provides instructions for assembling protein molecules and that this is virtually the same mechanism for all life forms.

B.1.27Explain that the similarity of human DNA sequences and the resulting similarity in cell chemistry and anatomy identify human beings as a unique species, different from all others. Likewise, understand that every other species has its own characteristic DNA sequence.

Objectives

Students will understand the following

-DNA is the molecule of heredity and protein synthesis

-DNA is composed of 4 bases adenine is complimentary to thiamine and guanine is complementary to cytosine.

-DNA is a double helix composed of complimentary strands, which replicate semiconservatively.

-DNA sequences can be altered by mutation, which alters the proteins made.

-Every organism has its own protein sequence.

Essential Questions

-What are the two primary purposes of DNA?

-What would DNA have to do to fulfill these purposes?

-What is a mutation, and how would it affect the DNA sequence?

-How could mutations be beneficial?

-How do we know the function, and structure of DNA?

-Could any other structure serve the same function as DNA?

-Why are enzymes needed for DNA to function properly?

Interdisciplinary connections

History-Discuss the historical figures involved in discovering DNA structure and replication understandings- students develop a timeline.

Speech- Students develop power points and present them to the class.

Chemistry- Students are taught the chemical structures involved in DNA and the way the chemicals interact during DNA function and replication.

Mathematics-Discuss the reasons mathematically 4 bases can be translated into 20 amino acids using a triplet code. .

Assessment Evaluation

Concept Map 10 pts

Assessment Questions 10 pts

Discussion 10 pts

Lab10 pts

Pre-test 10 pts

Post-test 50 pts

Presentation 25 pts

Extra Credit10 pts

Total125 Pts

Vocabulary

Ribose- Five carbon sugar included in RNA backbone C5 H10 O5

Deoxyribose-Five carbon sugar included in DNA backbone C5 H10 O4

Purine- Two ring nitrogen bases include Guanine and Adenine

Pyrimidines- One ring nitrogen bases include Cytosine and Thymine

Nucleotide- One unit of a DNA molecule includes 1 Phosphate, 1 Deoxyribose sugar, and one base.

Histone-Proteins that function in DNA packing and function

Nucleosome-a group of 8 histones that function as a single unit

Chromatin- DNA and histones in an unwound form, is able to function in RNA synthesis.

Chromosome- DNA and Histones that are packed to be able to be separated during replication, RNA can not be synthesized while DNA is in this form

Semiconservative Replication- DNA splits and each strand forms a new DNA unit

Replication Fork-The site where DNA is locally opened for replication to occur

Toipomerase-Enzyme that relieves stress on DNA during unwinding

Helicase-Enzyme that separates DNA strands

DNA polymerase- Enzyme that adds basses to unwound DNA strands (only works in a 3-5 direction.

RNA primer- Creates places for DNA polymerase to bond to on the lagging strand

Ligase- Enzyme that joins Okazaki fragments together

Okazaki fragments- The lagging strand is copied in pieces due to the DNA polymerase only reading in one direction

Leading strand- The DNA strand that has a free 3’ end

Lagging strand- The DNA strand that does not have a free 3’ end

Timeline

Day 1 / Pre-Test
Lecture on DNA Structure
Video Picture 51
Homework: Read 9.1-9.2
Review questions 1-6
Day 2 / Lab DNA extraction
Day 3 / Lecture Personalities involved in DNA discoveries
Online Discussion Who was the most important person involved in the understanding of DNA?
Students must reply to two other posts.
Homework Read 9.3
Answer Discussion Questions 7-16
Day 4 / Lecture DNA replication and mutations
Students must draw the replication fork with all enzymes involved
Make a concept map of chapter
Video DNA replication


Day 5 / Review discussion questions
Review previous lectures
Critical Thinking Questions in class
Practice test
Complete Study Guide
Day 6 / Post test DNA structure and replication
Work on Presentations
Day 7 / Work on presentations
Day 8 / Presentations Day 1
Day 9 / Presentations day 2

Resources

Lewis, R. 2010.Human Genetics Concepts and Applications ninth addition. McGraw-Hill. New York, NY.

Klug, W.S. 2009. Concepts of Genetics 9th addition. Pearson Education. Inc., San Francisco, CA.

Miller, K., Levine, J. 2005. Biology. Pearson Education. Inc., Upper Saddle River, NJ.

DNA necklace Lab, Carolina Biological Supply Company. Burlington, NC.

Web sites

Technology

Power Points- I use 3 power point presentations as a way to present materials to the students in a way that is interesting and visually stimulating. Students develop their own power points to present to their classmates.

Moodle- I use Moodle an online database and testing center for this lesson, for a discussion board, to administer pre and post tests, to display helpful resources and links, and as a place for the students to turn in completed work.

DNA extraction-This lab was purchased through Carolina, and included materials for students to extract and separate DNA from their cheek cells.

Concept Map-The students use to develop a concept map of the chapter.

Video on line –I use a few short online videos about DNA structure and replication that the students are able to access from Moodle.

Lesson Plans

#1 DNA Structure (2 days)

Overview

In this lesson students will learn about the chemical composition of DNA. These students have already been exposed to the basic nature of DNA in Freshman Biology, this class will go into much greater detail into the chemicals involved and how they interact with each other. This lesson involves a day of lecture and text exploration as well as a lab in which the students are able to extract and physically see their own DNA.

Standards-

B.1.26Demonstrate how the genetic information in DNA molecules provides instructions for assembling protein molecules and that this is virtually the same mechanism for all life forms.

B.1.27Explain that the similarity of human DNA sequences and the resulting similarity in cell chemistry and anatomy identify human beings as a unique species, different from all others. Likewise, understand that every other species has its own characteristic DNA sequence.

Objectives

Students will understand the following

-DNA is the molecule of heredity and protein synthesis

-DNA is composed of 4 bases adenine is complimentary to thiamine and guanine is complementary to cytosine.

-DNA is a double helix composed of complimentary strands

Procedures

Engage

Begin the lesson by asking the students what they know about the structure and purpose of DNA. Use what they already know to begin to build a more specific understanding of DNA’s chemical content. For example the students may know that DNA has a sugar phosphate backbone, but probably will not know that the sugar has 5 carbons, that are labeled in a specific order, and the phosphates are connected by phosphodiester bonds to the 3 and 5 prime carbons. During day 1 we will discuss this structure as well as its relation to histone proteins using a power point. On day two of the lesson will begin by asking what DNA looks like, then asking if the students think they can extract their own DNA easily.

Explore

The primary exploration in this lesson will occur during the DNA necklace lab(day 2). During this lab students will swab their cheek cells, add soap, and then ethyl alcohol. The DNA will condense out from the alcohol into a stringy looking substance.

Explanation/Elaboration

After the lab the students will answer questions that combine concepts from the lecture with the procedures in the lab. For example what is the chemical component in DNA that allows it to not dissolve in the alcohol.

Assessment/Evaluation

Formal- The Laboratory will be graded

Informal- during the lecture I will ask each student specific questions to gauge understanding.

Materials

Power Point- DNA structure

Lab- DNA Necklace Kit (Carolina)

Power Point DNA Structure

#2 Historical figures (1 day)

Overview

In this lesson students will explore the key historical figures involved in the current understanding of DNA structure and the experiments they used to gain this understanding. This is a one day lesson that involves a power point lecture about the historical figures and their experiments After the lecture students develop a timeline of these figures.

Standards-

B.1.24Explain that gene mutations can be caused by such things as radiation and chemicals. Understand that when they occur in sex cells, the mutations can be passed on to offspring; if they occur in other cells, they can be passed on to descendant cells only.

B.1.26Demonstrate how the genetic information in DNA molecules provides instructions for assembling protein molecules and that this is virtually the same mechanism for all life forms.

Objectives

-DNA is the molecule of heredity and protein synthesis

-DNA is composed of 4 bases adenine is complimentary to thiamine and guanine is complementary to cytosine.

-DNA is a double helix composed of complimentary strands, which replicate semiconservatively.

Procedures

Engage

Begin the class by asking questions such as; how long have we understood the importance of DNA? How do we know DNA is the hereditary material? What historical figures do you already know? Then discuss that for a long time the majority of humanity believed that protein was the hereditary material, because their was only 4 bases, but 20 amino acids. It made much more sense that the amount of variation that exist is from the 20 Amino acids, until we realized how those bases coded for proteins.

Explore

The students will continue to explore the contributions of different personalities using both their textbooks, and online resources. The students are required to develop a timeline using at minimum the persons discussed in class, and also at least two others. The students have the option to use a power point, a word document, or make the timeline by hand.

Explanation/Elaboration

On Moodle the students are required to complete a discussion board answering the question; who is the most important historical figure involved in DNA discovery, and why? The students need to write one journal entry, and respond to two others.

Assessment/Evaluation

Formal- Timeline

Formal- Discussion Board

Informal- Asking engaging questions to each student during the lecture

Materials

Power Point- Historical Figures

Moodle- Journal entry

Power Point Historical Figures

#3 Replication and Mutation (1 day)

Overview

In this lesson students will learn about DNA replication and Mutation. The students will have to be able to draw the DNA fork, including the primary enzymes involved and their functions. The students will also learn more detail about possible mutations that can occur during DNA replication. This lesson will conclude with the students bringing all the materials discussed in this unit together by using an online concept map.

Standards-

B.1.23Understand that and describe how inserting, deleting, or substituting DNA segments can alter a gene. Recognize that an altered gene may be passed on to every cell that develops from it, and that the resulting features may help, harm, or have little or no effect on the offspring’s success in its environment.

B.1.24Explain that gene mutations can be caused by such things as radiation and chemicals. Understand that when they occur in sex cells, the mutations can be passed on to offspring; if they occur in other cells, they can be passed on to descendant cells only.

Objectives

Students will understand

-DNA sequences can be altered by mutation, which alters the proteins made.

-Every organism has its own protein sequence.

-The DNA replication fork and the primary enzymes associated with it

Procedures

Engage

Begin the class by asking the students why variation exists in life. Several students may say it is because different traits exist or different genes exist in nature. Then ask what causes these differences. The ultimate answer being sought is mutations. Then lead the discussion toward replication. When during the cell cycle does replication take place? How often does replication take place? How does replication take place?

Explore

During the power point lecture we will focus on the enzymes involved in replication, the replication fork, the proof for semi-conservative replication, and the type of mutations that can occur. After we finish discussing each topic I will show a short video to further develop the student’s knowledge of the topic. The students are also expected to read about the topic in their textbooks.

Explanation

The students are expected to be able to draw the replication fork and label the following enzymes;toipomerase, helicase, DNA polymerase, DNA ligase, and DNA primers. The students are also expected to label the direction that DNA polymerase is able to read and copy DNA strands, and the method of copying the lagging strands of DNA (Okazaki fragments).

Elaboration

After the lesson is complete the students will make a concept map of the entire unit using an online concept map program This program uses bubbles linked by lines representing specific relationships.

Assessment/Evaluation

Formal- Replication Forks and Concept Maps

Resources

Power Point DNA replication and Mutation

Web site

Online tutorials

#4 Presentations (4 days)

Overview

In this section of the unit students will develop power points using a subject that is directly related to the unit. Then each student will present his or her power point to the class. The students will be graded based on a RUBRIC, which uses specific grading criteria. The criteria include; time limit, accuracy, aesthetics of the power point, presentation skills, and peer evaluations. The students are able to choose their topics based on their interests, but I will approve these topics, based on topics I believe the students have the opportunity to present successfully. The students will use these same criteria to grade each other.

Standards

B.1.23Understand that and describe how inserting, deleting, or substituting DNA segments can alter a gene. Recognize that an altered gene may be passed on to every cell that develops from it, and that the resulting features may help, harm, or have little or no effect on the offspring’s success in its environment.

B.1.24Explain that gene mutations can be caused by such things as radiation and chemicals. Understand that when they occur in sex cells, the mutations can be passed on to offspring; if they occur in other cells, they can be passed on to descendant cells only.

B.1.26Demonstrate how the genetic information in DNA molecules provides instructions for assembling protein molecules and that this is virtually the same mechanism for all life forms.