dna teacher's guide discovery education

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T E AC H ER/ FAC I L I TATORS GUIDE

DN A:The MasterMolecule of Life

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D N A : T h e M a s t e rM o l e c u l e of Life

Video and Guide Produced by:Ancient Lights Educational Media

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C O N T E N T S

Introduction and Summary 1

Curriculum Standards 1

Teacher Preparation/Instructional N otes 2

Student Pr e p a r a t i o n 2

Pr e - t e s t 2

Student Objectives 3

Introducing the Video 3

Fo l l o w-Up Discussion 4

Extended Learning Activities 4

Blackline Master Descriptions 5

Answer Ke y 5

Script of Video Narration 7

Video Quiz 11

This video is closed captioneda 2

The purchase of this video program entitles the user to the right to reproduce orduplicate, in whole or in part, this teachers guide and the blackline master handouts

that accompany it for the purpose of t eaching in conjunction with this video,DNA:The Master Molecule of Life.This right is restricted only for use with this videoprogram. Any reproduction or duplication in whole or in part of this guide and theblackline master handouts for any purpose other than for use with this videoprogram is prohibited.


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D N A: THE MASTER MOLECULE OF LIFEGrades 5-9

Viewing Time: 14 minutes

Lesson Three: Religion

INTRODUCTION AND SUMMARY

The diverse life forms that inhabit the earth share the commonbond of being based on DNA. This program explores the structureof the DNA molecule. It demonstrates how DNA subunits are usedto create genetic code words and sentences. Students also discoverhow the instructions stored in genes are transcribed into messengerRNA and then, with the help transfer RNA, are translated into pro-teins which perform myriad tasks inside cells.

C U R R I C U LUM STA N DA R D S

The design of this program was guided by the curriculum standardsof the States of Texas, California and Illinois. The AmericanAssociation for the Advancement of Science recommendations forimproving biological science content were followed throughout thisseries: "Biology: The Science of Life". In accordance with these guide-lines we have attempted to help students:

1. Understand the molecular basis of heredity.

2. Develop an increased understanding of how cells work.

3. Recognize and investigate problems and propose solutions based onreason, experimentation, and evidence.

4. Express and interpret information and ideas.

5. Use computer networks and library research to access information.

6. Relate biological science to everyday life experience.


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T E ACHER PREPA R ATION/INSTRUCTIONAL NOTES

Before presenting this program to your students, we suggest thatyou review the subject of cell structure and function. We also adviseyou to preview the video and review the guide and accompanyingblackline masters in order to familiarize yourself with their content.As you review the materials presented in this guide, you may find itnecessary to make some changes, additions, or deletions to meetthe specific needs of your class. We encourage you to do so, for onlyby tailoring this program to your class will they obtain the maximuminstructional benefits afforded by the materials.

It is also suggested that the video presentation take place before theentire group under your supervision. The lesson activities grow out

of the context of the video; therefore, the presentation should be acommon experience for all students.You should also duplicate selected"hand out" materials from the blackline masters included in this guide.Set up a "Learning Center" with diagrams and models that depictDNA, RNA and proteins.

STUDENT PREPA R AT I O N

Before viewing D N A: The Master Molecule of Life

1. Have students explore the "Learning Center".

2. It is important to have students to read about DNA and RNA in

their in their textbooks before viewing this lesson.

P R E T E S T

An optional pretest is provided (Blackline Master 1). This test willhelp you determine the level of student comprehension prior toparticipating in this lesson. An Answer Key appears on page 5 ofthis Teachers Guide.

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STUDENT OBJECTIVES

After viewing the video and participating in the follow-up activitiesstudents should be able to:

1. Explain the chemical basis of the genetic code.

2. Describe the relationship between genetic code words andamino acids.

3. Describe the relationship between the linear order of code wordsin a gene and the order of amino acids in a protein.

4. Explain the role of messenger RNA.

5. Explain the role of transfer RNA.

6. Compare and contrast Replication, Transcription and Tr a n s l a t i o n .7. Discuss the importance of proteins in living cells.

INTRODUCING THE VIDEO

1. Introduce the program by pointing out the following things: DNA isthe master molecule of life because it controls nearly all cell activities.Because DNA is self-replicating, genetic information is passed onfrom cell to cell and from generation to generation. DNA is able tocontrol cell activities because it stores instructions for making pro-teins. There is a region of DNA or GENE for every protein madeby cells. The cell produces proteins only when they are needed.It does this by sending chemical signals to the DNA which activategenes. Most proteins are enzymes. Enzymes control the rates of thechemical reactions that take place inside the cell: In fact very fewchemical reactions in cells occur without the help of enzymes.Po i n tout that if only half of the roughly 100,000 human genes coded forenzymes that would mean 50,000 different types of chemicalr e a c t i o n s would be under the direct control of DNA. Let studentsknow the program they are about to see presents a "bare bones"glimpse of how transcription and translation occur. The topic hasbeen simplified to make understanding of this difficult subject aseasy as possible.

2. Hand out the Crossword Puzzle (Blackline Master 3 )

View the video: Running time of the program is 14 minutesfollowed by a short (1 minute) optional video quiz.

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F O L LO W-UP DISCUSSION

It is recommended that you involve students in a discussionimmediately after viewing the video:

1. Discuss how the genetic code works.

2. Discuss how the proteins called enzymes carry out the actualwork of regulating the activities of the cell.

EXTENDED LEARNING AC T I V I T I E S

A. In order to express and communicate ideas and improve researchskills use the INTERNET and other resources to prepare papers ororal reports on the following subjects:

1. The human genome project

2. Deciphering the genetic code

3. DNA fingerprinting

4. Genetic engineering

B. Microscope Work: Examine a slide of the salivary gland chromo-somes of the fruitfly Drosophilia melanogaster. These chromosomesare actually polyploid meaning that many DNA strands exist in eachchromosome. As a result, they are very thick. Look for the bands

that may represent genes and the "puffing" that indicates gene activity.



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DESCRIPTION OF BLACKLINE MAS T E R S

Blackline Master 1, is a Pre-test that, when compared to the quizresults, will help you gauge student progress.

Blackline Master 2, is a Vocabulary Worksheet that will introducestudents to unfamiliar words used in the program, or wordspertaining to the subject of the program they may encounter inoutside reading.

Blackline Master 3, is a Crossword Puzzle that challenges studentsto use some of the words from the vocabulary worksheet thataccompanies in this program.

Blackline Master 4, is a Test for evaluating student progress.

Blackline Master 5, is a printed version of the Video Quiz t h a tappears at the end of this program. The video quiz encouragesattentiveness and tests information retention.

ANSWER KEY

Blackline Master 1, Pre-test

1. Tr u e

2. False, it is the same in every organism.

3. False, it is based on the 4 different subunits of DNA.

4. False, all genetic code words are three letters long.

5. Tr u e

Blackline Master 2, Vocabulary Activities

1. Enzymes

2. Molecule

3. Messenger RNA

4. Transfer RNA

5. Synthesis

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7. Amino Acid: The subunits that are chemically bonded together inproteins. The order amino acids follow one another in protein chains

is what determines how the protein works.

8. Nucleotide Subunit: The Subunits that make up DNA. Each nucleotidehas a phosphate group, a deoxyribose sugar group and a nitrogen-containing base; either Adenine, Thymine, Cytosine or Guanine.

9. Macromolecule: A very large molecule may form thousands ofatoms. DNA, messenger RNA and proteins are examples ofmacromolecules.

0. Replication of DNA: The process that occurs when DNA makes anexact copy of itself before a cell divides.

Blackline Master 5, Video Quiz

1. Tr u e

2. False, genetic code words represent different amino acids

3. Tr u e

4. False, each chromosome may possess thousands of genes

5. Tr u e

Script of Video NarrationD N A: THE MASTER MOLECULE OF LIFE

Living things are very diverse and are found in an incredible array ofcolors, shapes, and sizes. Yet, in spite of their great differences, if youlook closely enough they are actually quite similar to one another. Aslong ago as the 1830s scientists had begun to realize this fact whenthey discovered that all living things are made from cells. By the mid-dle of the 20th century even more similarities were found when newscientific tools let researchers examine the molecules found inside ofcells. One molecule in particular called Deoxyribonucleic Acid orDNA captured their attention. Scientists discovered that DNA uses agenetic code to chemically store the information cells need to per-form their many life-supporting activities. Researchers also discoveredthat this genetic code is truly u n i v e r s a l because it is used in every

living cell: from lowly bacteria like these, to the complex cells ofanimals and plants. Now, let us learn more about the amazing DN Amolecule... and find out how it works.



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D N A: CHROMATIN, CHROMOSOMES, ANDNUCLEOTIDE SUBUNITS

In the cells of higher organisms almost all the DNA is located insidethe nucleus in the substance called c h r o m a t i n. Before a cell repro-duces the chromatin changes into the separate structures seen herethat are known as c h r o m o s o m e s . Inside a chromosome the DNA,along with some proteins, is neatly packaged: It is twisted and foldedover and over again. Something like this is possible because DNA isa very large molecule: a m a c r o m o l e c u l e . A closer look shows that theDNA molecule is actually made up of two separate strands that windaround and around one another creating a shape called adouble helix.Each of the two DNA strands is made up of smaller chemical s u b-u n i t s called n u c l e o t i d e s which are joined together, one after another,

in a very precise order.Only four different subunits are used in DNAbut each one can be found tens of thousands of times in the hugemolecule. To help visualize molecules, scientists use structural for-m u l a s like this one to show how their atoms are bonded together.For example, this structural formula shows that each DNA subunitcontains a phosphate group composed of a single atom of the ele-ment Phosphorus, P, bonded to 4 atoms of the element oxygen, O,plus a single Hydrogen atom. Each DNA subunit also contains asugar group called d e o x y r i b o s e that is made from five carbon atoms,one oxygen atom and several hydrogen atoms all bonded togetheras shown here. The individual DNA subunits in a strand are linkedtogether by strong chemical bonds between their phosphate andsugar groups these bonds form the "backbone" of the DNA mole-cule. Each of the four DNA subunits possesses a nitrogen containingbase. The chemical names of the bases are thymine, cytosine, ade-n i n e , and g u a n i n e : abbreviated T, C, A and G. These bases arealways found in pairs linked to one another by weak chemical bonds,called hydrogen bonds, that exist between the bases in each strand.The bases always pair up the same way so that if one DNA strandhas an A the opposite strand will always have a T in exactly the sameplace. Likewise a G in one strand is always paired with a C in thesame place in the opposite strand. Because of the way base pairingoccurs DNA molecules end up having two exactly opposite or c o m-

p l e m e n t a r y strands. As we will soon discover it is the precise orderthe subunits appear in the DNA strands that is the key to the g e n e t i cc o d e : and the genetic code is the key to life itself.


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D N A, GENES AND PROTEINS

In the last century researchers studying genes, the units of heredity,which determine such things as hair color, eye color, and blood typemade two extremely important discoveries. The first was that g e n e sare made from DNA. The second was that each gene holds thecoded instructions for making a different protein. Proteins are madeup of long chains of amino acids of which there are 20 differentkinds. Living organisms use proteins for a lot of different things :They can be used for building cell parts, repairing damage, fightingdisease and regulating the speed of the tens of thousands of chemicalreactions that take place inside of cells. Each chromosome in a cellhas many different genes and genes themselves are simply certainregions of a DNA molecule. Genes determine the order amino acids

will appear in a particular protein chain and it is this order whichgives the protein the ability to do its job. Now let us see how DNAstores instructions in the unique biological language of the genetic code.

THE GENETIC CODE

The subunits of a DNA molecule: A, T, C, and G are the four l e t t e r sof the genetic code alphabet. Of course the subunits are chemicalcompounds not actual letters. Nevertheless they can be used justlike letters to "spell out" genetic code w o r d s . Most of the 64 codewords used by living things represent, or "code for", amino acids and

each of these words is only three letters long. For example A-A-A isa code word for the amino acid phenylalanine, G-C-T for the aminoacid arginine, C-T-C for glutamic acid and T-A-C for the amino acidmethionine. A protein made from these amino acids could have ag e n e , or s e n t e n c e of code words, like this "written" in one of theDNA strands. This sentence informs the cell that this particular pro-tein is to be made using only these four amino acids in this exacto r d e r. replication of DNA All the DNA in a cell can be thought of asa LIBRARY containing books of instructions which tell the cell howto make the proteins it needs to stay alive. In fact every time a celldivides its DNA is copied or r e p l i c a t e d so that each new cell willhave a full library of instructions.


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BRIEF REVIEW

Let's briefly review how DNA stores instructions: The DNA mole-cule of a single chromosome can be thought of as one b o o k from thecell's library of instructions. A chromosome can contain thousandsof genetic code s e n t e n c e s or g e n e s that determine the order aminoacids will appear in proteins. Such sentences are written using g ene t icc o de w o r d s ...all of which are just three letters long. These wordsare codes for any of 20 different amino acids and, of course, thele t t e r s with which the words are written are the four nucleotidesubunits of DNA.

MESSENGER RNA, TRANSFER RNA, AND PROTEIN SYNTHESIS

Inside living cells the actual process of making proteins involves sev-eral different steps because the instructions for making proteins arestored in the nucleus but the proteins themselves are made, ors y n t h e s i z e d , in the cytoplasm. This means cells must have a way tomove information out of the nucleus and into the cytoplasm. As itturns out cells use a special molecule for this task, called messengerRNA. RNA, or ribonucleic acid, is very similar to DNA but RNA hasonly a single strand, it contains the sugar r i b o s e instead of d e o x y r i-b o s e , and a base called u r a c i l replaces the Thymine found in DNA:So the RNA alphabet is A- U -C-G not the A-T-C-G used by DNA.Whenever a cell needs more of a certain protein it sends a chemical

signal to the nucleus which causes the gene for that protein to be"switched on". When this happens the DNA code words in the geneare copied into the RNA code words, or c o d o n s , of messenger RNA:This process is called genetic transcript ion. After the gene is copied,the messenger-RNA carries the protein making instructions to aribosome in the cytoplasm: Ribosomes are the organelles whereproteins are made. However, just the fact that the messenger RNAhas reached a ribosome is not enough for the protein to start beingmade. In order for the message to be t r a n s l a t e d a third kind of RNA,called t r a n s f e r RNA, is needed.Transfer RNAs are small RNA mole-cules that can pick up amino acids and transfer them to the messen-ger RNA on the ribosome. There are almost as many transfer RNAs

as there are DNA code words. In fact each of the different transferRNAs has a different a n t i c o d o n which is basically a DNA code wordwritten using the letters of the RNA alphabet. Transfer RNAs carryingamino acids match-up their a n t i c o d o n s to the messenger RNA

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codons as the ribosome moves along the message: As a result theamino acids carried by the transfer RNAs will be put into the protein

chain in exactly the right order. Once the protein is finished it isready to perform its job in the cell and as the protein goes to worka new chemical signal is sent back to the nucleus that "switches off"the gene for that particular protein.

C O N C LU S I O N

As we have just learned DNA performs an essential role in the livesof all living things. It stores huge amounts of information in theunique biological language called the genetic code. DNA's geneticinformation is transcribed into messenger RNA which carries it to the

ribosomes where, with the help of transfer RNA, new proteins aremade that perform thousands of tasks inside of cells. But DNA iseven more amazing because it can make exact copies of itself. As aresult genes and the instructions they hold are passed on; not justfrom old cells to new cells but from one generation to the next.

VIDEO QUIZ

1. True of False?The four subunits of DNA are used as the "letters"of the genetic code alphabet.

2. True of False?Genetic code words represent different proteins.

3. True of False?Translation takes place on ribosomes.

4. True of False?There is usually one gene on each chromosome.

5. True of False?DNA is transcribed into messenger RNA in the nucleus.


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P R E -T E S T

D i r e c t i o n s : Answer each question TRUE OR FA L S E :

1. Genes are made from DNA.

2. The genetic code used in the cells of mushrooms is quitedifferent from genetic code used in human cells.

3. The "alphabet" of the genetic code uses the 20 differentamino acids for letters.

4. Genetic code words are of different lengths according tothe information they contain.

5. DNA chemically stores instructions for making proteins.

D N A: The Master Molecule of Life

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D N A: The Master Molecule of Life2001 Ancient Lights Educational Media

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VO C A B U LA RY WORKSHEET

A d e n i n e : A nitrogen containing base found in one of the

nucleotide subunits of DNA. Adenine is the "A" of thegenetic code alphabet.

Amino Acid: The subunits that are chemically bondedtogether in proteins. The order of amino acids in a proteinis what gives it the ability to do its job.

A n t i c o d o n : The three letter word of a transfer RNA thatcorresponds to the amino acid it carries. The anticodonmatches up with the codon of the messengerRNA.

B a c t e r i a : Simple, one-celled, organisms that lack a nucleusbelonging to the kingdom Monera.

Cell Division: The process that results in two cells being

formed from one cell. Cell reproduction.

C h e m i c a l : Chemicals are substances made from combi-nations of different elements.

Chemical Bonds: The way in which atoms are joined toone another: For example, in water an atom of oxygen is

joined to two atoms of hydrogen by chemical bonds.The subatomic particles called electrons are responsiblefor creating chemical bonds.

Chemical Re a c t i o n s : Events in which chemical bonds arebroken, rearranged and reformed. Matter is changed bychemical reactions: This is what happens when chemical

compounds react with one another and new compoundsare formed.

C h r o m a t i n : Chromatin is made up of the tangled, thread-like, coils of chromosomes. Chromatin contains DNA pluscertain proteins.

C h r o m o s o m e s : Chromosomes are worm-shaped struc-tures that develop from chromatin before cells divide.Chromosomes contain DNA and protein. Human bodycells have two full sets of 23 different chromosomes.

C o d o n : A code word of messenger RNA that representsan amino acid.

C o m p l e m e n t a r y : Two parts of a jigsaw puzzle fit togetherto make a whole: Therefore they are called complementaryparts. DNA has two complementary strands because theyare exact opposites of one another.

C y t o p l a s m : All the protoplasm located outside the nucleus.

C y t o s i n e : A nitrogen containing base in a nucleotide

subunit of DNA.Cytosine is the "C"of the geneticcode alphabet.

Deoxyribonucleic Acid (DNA): A long molecule shapedlike a twisted ladder(double helix). The plans for runningand reproducing cells are chemically stored in the DNA.DNA is found mostly in the nucleus but small amounts ofDNA are found in mitochondia and chloroplasts.

De o x y r i bo s e: The sugar part of a a DNA nucleotide subunit.

Double Helix: The double spiralshape of the DNAmolecule.

E n z y m e s : Proteins that control the rates of chemical reac-tions in cells. Most proteins in a cell are enzymes. Digestive

enzymes such as pepsin and trypsin are produced byspecialized cells. These enzymes are exported from cellsto break down food in the digestive tract.

G e n e : A region of a DNA molecule that stores the instruc-tions for making a particular protein. Genes are also knownas the units of making a particular protein. Genes are alsoknown as the units of heredity.

Genetic Code: The chemical language of the cell. DNAstores its instructions in the genetic code.

Genetic Code Wo r d : Three DNA nucleotide subunits in ar o w, such as AAA or AGA, that represent amino acids.

Genetic Tr a n s c r i p t i o n : The process of copying a gene intome s s e n g e r- R N A .

G u a n i n e : A nitrogencontaining base found in a nucleotidesubunit of DNA that is the "G" of the genetic code alphabet.

H e r e d i t y : Characteristics that are passed on fromparents to their offspring. Genes are called the "unitsof heredity .

H er ed i ta r y : Passed on from one generation to the next.

Hydrogen Bond: A type of weak chemical bond. Hydrogenbonds exist between the two strands of the DNA molecule

and between the messenger RNA codons and the transferRNA anticodons.

M o l e c u l e : A combination of two or more atoms bondedtogether by strong chemical bonds (covalent bonds).

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M a c r o m o l e c u l e : A very large molecule made from thou-sands of atoms. DNA, messenger RNA and proteins areall examples of macromolecules.

Messenger RNA (m-RNA): Messenger RNA carries instruc-tions for making proteins from the nucleus to a ribosome.

Nit rogenous Bases: The nitrogen containing bases of theDNA nucleotide subunits whose chemical names areAdenine, Thymine, Cytosine, and Guanine.

N u c l e a r : Refers to the nucleus.

Nucleic Acids: DNA or RNA nucleus (Plural: Nuclei)A rounded structure located in the cytoplasm. The nucleusis the cell's control center because it is where most of theDNA is located.

N u c l e o l u s ( N e w- k l e e -oh-lus): "Little Nucleus" The area ofthe nucleus where ribosomes are made. Cells can havemore than one nucleolus.

Nucleotide Subunit: The Subunits that make up DNA.Each nucleotide has a phosphate group, a deoxyribosesugar group and a nitrogencontaining base; eitherAdenine, Thymine, Cytosine or Guanine.

O r g a n e l l e s : "Little Organs". Structures in the cytoplasmsuch as mitochondria, ribosomes, chloroplasts, and Golgibodies where different tasks are performed in the cell.

Pr o t e i n s : Molecules made up of long chains of amino

acids(polypeptides). Proteins build living material, fight dis-ease, and help transport things out of the cell. The impor-tant class of proteins called e n z y m e s act to control therates of chemical reactions. Most proteins are enzymes.

Replication of DNA: The process that occurs when DNAmakes an exact copy of itself before cell division.

R i b o s o m e s : The organelles where proteins are assembled.

Ribonucleic Acid: A type of nucleic acid that contains thesugar ribose instead of deoxyribose, has one strand andthat has the base Uracil instead of Thymine.

R i b o s e : A sugar group found in RNA nucleotide subunits.

Structural Formula: A diagram used by chemists thatshows how atoms are arranged in molecules.

S y n t h e s i s : To make complex substances from simpler parts.Proteins are synthesized from amino acid subunits. DNA issynthesized from nucleotide subunits.

S u g a r-Phosphate Bonds: Strong (covalent) bonds betweenthe deoxyribose sugar of one nucleotide and the phosphategroup of the adjoining nucleotide is what forms the "back-

bone" of the DNA molecule.

Terminator Codons: Every messenger RNA message endswith one of three different "terminator" codons: UAG, UA Aor UGA. Since there are no transfer RNAs with anticodonsto match these messenger RNA codons protein synthesisstops whenever a terminator codon is reached.

T h y m i n e : A nitrogen containing base found in one of thenucleotide subunits of DNA. Thymine is the "T" of thegenetic code alphabet.

Transfer RNA (t-RNA): A small RNA molecule that can pickup amino acids. By matching the transfer RNA anticodon to

the messenger RNA codon the amino acid is put into theprotein chain correctly.

Tr a n s l a t i o n : The process of making proteins using theinstructions of messenger RNA molecule.

U r a c i l : A nitrogencontaining base used in RNA moleculesinstead of Thymine.


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VO C A B U LA RY AC T I V I T Y

From the vocabulary list find the correct word to fill

in the blanks.

1. are proteins that control the

rates of chemical reactions.

2. Two or more atoms strongly bonded together

is called a

3. Instructions from DNA are carried to ribosomes by

molecules of

4. Amino acids are picked up by special RNA

molecules called

5. The process of making something from simple

subunits is called

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CROSSWORD PUZZLE

A c r o s s :

1. A messenger-RNA code word

is called a .

2. is the process that

takes place when proteins are made

from the instructions of messenger-R N A .

3. Tr a n s f e r-RNA carries

to the messenger- R N A .

4. is the process that

takes place when DNA makes a copyof itself.

5. All genetic code words have

" l e t t e r s " .

6. Fo u r subunits are

needed to make a DNA molecule.

D o w n :

1. The DNA molecule is called a

because it isvery large.

is the process by which

DNA is copied into messenger RNA.

3. Most of a cell's DNA is found in its

.

4. Proteins are made on organelles called

.

5. A region of the DNA molecule that

stores instructions for a protein is called a

.

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P R E -T E S T

D i r e c t i o n s : Define each of the following.

1. Messenger RNA

2. Genetic code word

3. Anticodon

4. Transfer RNA

5. Pr o t e i n s

6. Ribosome

7. Amino acid

8. Nucleotide Subunit

9. Macromolecule

10. Replication of DNA


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