Course: Biology Agricultural Science & Technology



Course: Biology Agricultural Science & Technology

Unit: DNA

State Standard: Students will understand that genetic information coded in DNA is passed from parents to offspring by sexual and asexual reproduction. The basic structure of DNA is the same in all living things. Changes in DNA may alter genetic expression.

State Objectives: Explain how the structure and replication of DNA are essential to heredity and protein synthesis.

a. Use a model to describe the structure of DNA.

b. Explain the importance of DNA replication in cell reproduction.

c. Summarize how genetic information encoded in DNA provides instructions for assembling protein molecules.

e. Relate the historical events that lead to our present understanding of DNA to the cumulative nature of science knowledge and technology.

Unit Objectives:

A. Describe the structure of a DNA molecule and the history of its discovery.

B. Explain the process of DNA replication and understand its relevance to cell division.

C. Describe the structure of RNA and identify the steps associated with protein synthesis.

Materials Needed (Equipment):

• Pre-cut paper nucleotide bases for DNA activity – Print or copy enough so that each person in the class has one nucleotide base (Click here for nucleotide activity cards)

• Red and black licorice sticks, colored marshmallows or gummy bears, toothpicks and string. (Click here for the Candy DNA Lab Activity)

• The following supplies are for the DNA Extraction Lab (Optional)

Split green peas

Table Salt

Cold water

Blender

Strainer

Detergent (Dawn)

Meat tenderizer

Rubbing alcohol

Test tube

Wooden skewers

Mixing bowl

Beaker

Facilities:

• Classroom

• PowerPoint

• Projector

Interest Approach:

• A: Take a stack of books and have students imagine how much information is held in the stack of books. Explain how small a molecule of DNA is. (You need a microscope to see a cell). Explain that a molecule of DNA has much more information on it than in the stack of books on the table and that DNA is what makes living organisms what they are.

• B: Demonstrate or have groups do a DNA Extraction Lab

o Click here to follow the link to the DNA Extraction Lab

Objective A: Identify the structure of a DNA molecule.

|Curriculum (Content) |Instruction (Methodology) |

|(What to teach) |(How to teach) |

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| |Have a class discussion on what students know about DNA and list |

| |on board. |

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|A1 |Have a class discussion about what DNA is made up of. |

|A2 |Have a student draw a diagram of DNA on the board. |

|Deoxyribonucleic Acid | |

|DNA is the molecule responsible for controlling the activities of|A1. PPT Slide 1 |

|the cell |A2. PPT Slide 2 |

|It is the hereditary molecule | |

|DNA directs the production of protein | |

|A3 | |

|Structure of DNA | |

|In 1953, Watson and Crick proposed that DNA is made of two chains| |

|of nucleotides held together by nitrogenous bases. | |

|Watson and Crick also proposed that DNA is shaped like a long | |

|zipper that is twisted into a coil like a spring. | |

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| |A3. PPT Slide A3 |

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|A4 | |

|Structure of DNA | |

|Because DNA is composed of two strands twisted together, its | |

|shape is called double helix. | |

|A double helix resembles a twisted ladder. | |

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|A5 | |

|Nucleotides | |

|DNA is made up of subunits called nucleotides | |

|Nucleotides consist of the backbone, which is made of sugar | |

|(deoxyribose) and phosphate, as well as a nitrogenous base | |

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| |A4. PPT Slide A4 |

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|A6 |[pic] |

|Nucleotide | |

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| |A5. PPT Slide 5 |

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|A7 | |

|How Did DNA Get its Name? | |

|Based on what you just learned, how do you think deoxyribonucleic| |

|acid (DNA) got its name? (Because of the sugar in the backbone of| |

|the DNA molecule called deoxyribose) | |

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|A8 | |

|Nucleotides | |

|A nitrogenous base is a carbon ring structure that contains one | |

|or more atoms of nitrogen. | |

|In DNA, there are four possible nitrogenous bases: adenine (A), | |

|guanine (G), cytosine (C), and thymine (T). | |

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|A9 | |

|Nucleotide Sequence | |

|The four nucleotides are represented by the first letter in their| |

|name |A6. PPT Slide 6 |

|A – Adenine |Discuss the diagram of the nucleotide and help students identify |

|G – Guanine |each component. |

|T – Thymine |[pic] |

|C – Cytosine | |

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|A10 |A7. PPT Slide 7 |

|Nucleotide Sequence |Either have students write an answer to this question in their |

|In DNA, Adenine always pairs with Thymine |notes or on a sheet of paper, or discuss as a class. |

|Cytosine always pairs with Guanine | |

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|A11 | |

|Nucleotides | |

|Nucleotides stack on top of one another forming the double helix,| |

|or twisted ladder | |

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| |A8. PPT Slide 8 |

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| |[pic][pic][pic][pic] |

|A12 | |

|[pic] | |

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|A13 | |

|DNA Building | |

|Click here to link to a DNA building activity online! | |

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| |A9. PPT Slide9 |

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| |A10. PPT Slide 10 |

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| |[pic] |

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| |A11. PPT Slide 11 |

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| |[pic] |

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| |A12. PPT Slide 12 |

| |On the view of the DNA diagram, have students identify the |

| |individual components of the DNA molecule |

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| |A13. PPT Slide 13 |

| |On this link, have students create a DNA molecule and practice |

| |matching nucleotide bases |

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| |Do Candy DNA Activity (See below) |

Activity:

How to Make a DNA Model Using Candy

Here's How:

1. Gather together red and black licorice sticks, colored marshmallows or gummy bears, toothpicks and string.

2. Assign names to the colored marshmallows or gummie bears to represent nucleotide bases. There should be four different colors each representing either adenine, cytosine, guanine or thymine.

3. Assign names to the colored licorice pieces with one color representing the pentose sugar molecule and the other representing the phosphate molecule.

4. Cut the licorice into 1 inch pieces.

5. String half of the licorice pieces together lengthwise alternating between the black and red pieces.

6. Repeat the procedure for the remaining licorice pieces to create a total of two stands of equal length.

7. Connect two different colored marshmallows or gummy bears together using the toothpicks.

8. Connect the toothpicks with the candy to either the red licorice segments only or the black licorice segments only, so that the candy pieces are between the two strands.

9. Holding the ends of the licorice sticks, twist the structure slightly.

Tips:

1. When connecting the base pairs be sure to connect the ones that pair naturally in DNA. For example, adenine pairs with thymine and cytosine pairs with guanine.

2. When connecting the candy base pairs to the licorice, the base pairs should be connected to the licorice pieces that represent the pentose sugar molecules.

|A14 |A14. PPT Slide 14 |

|Go Get It Moment! |Place your pre-cut nitrogen base papers somewhere in the room where |

|When you hear “Move it!” you will have 30 seconds to come get one |students can access them easily and follow the prompt on the PPT slide|

|piece of paper with an A, G, T, or C on it. |14. When you are ready for the students to get started, click onto |

|Then find someone else in the room whose letter correctly matches with|the next slide and there is an automatic 30 second timer. |

|your nucleotide letter and stand by that person. | |

|What are the questions? | |

|“Move it!” | |

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|A28 | |

|Go Get It Moment! |A28. PPT Slide 28 |

|When you hear “Double Helix”, you will have 1 minute to make a |Follow the prompt on the PPT slide 28 and when you are ready for the |

|classroom DNA strand by standing next to another pair of nucleotides |students to get started, click onto the next slide and there is an |

|What questions are there? |automatic timer for 1 minute. Have the students keep their nucleotide|

|“Double Helix” |paper letter and remember their partner and their place in the DNA |

| |strand for a future activity. |

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Objective B: Explain the process of DNA replication and understand its relevance to cell division.

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| |Students should have already learned about mitosis and meiosis. |

| |Answers should refer back to Interphase in cell division where DNA |

| |replication occurs in order for the cell to divide with the |

| |appropriate amount of DNA. |

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| |B45. PPT Slide 45 |

|B45 | |

|DNA Replication | |

|In order for cells to divide, DNA must be able to make exact copies of| |

|itself | |

|This process is known as DNA Replication | |

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|B46 |B46. PPT Slide 46 |

|DNA Replication | |

|DNA Replication occurs before mitosis and meiosis | |

|Replication results in two identical DNA daughter strands from one | |

|mother strand | |

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|B47 | |

|Process of DNA Replication | |

|The DNA strand is unzipped at the hydrogen bonds by an enzyme named |B47. PPT Slide 47 |

|helicase. | |

|Nucleotides in the nucleus then find their corresponding nucleotides | |

|on each of the two open DNA strands and produce two new DNA double | |

|helixes. | |

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|B48 | |

|Link to DNA Replication Animation | |

|Click here to see how DNA Replication works | |

| |B48. PPT Slide 48 |

| |Show Internet animation to illustrate the process of DNA replication |

Objective C: Identify the steps associated with protein synthesis.

|Interest Approach for Objective C: | |

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| |Discuss or write on the board foods high in protein. (Eggs, meat, |

| |beans, etc.) |

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| |Discuss or write on the board reasons why protein is an important |

| |nutrient. (Good for muscles, hair, nails, etc.) |

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| |Discuss where protein comes from. |

| |(Likely, students have never considered this question before now. |

| |Some may say that they get protein from the food they eat. Follow |

| |this with the question, “where did the plant or animal get the protein|

| |from?”) |

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| |C49. PPT Slide 49 |

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|C49 | |

|Protein Synthesis | |

|The main job for DNA is to direct the production of protein | |

|Protein makes tissues and organs and carries out the organism’s | |

|metabolism | |

|Proteins are polymers (chains) of amino acids | |

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|C50 | |

|Protein Synthesis |C50. PPT Slide 50 |

|The sequence of nucleotides in each gene contains information for | |

|assembling the string of amino acids that make up a single protein | |

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|C51 | |

|RNA |C51. PPT Slide 51 |

|RNA is a nucleic acid composed of nucleotides that is crucial in |On the board, make two columns. |

|making protein |Write DNA on top of one column and RNA at the top of the other column.|

|There are three differences between DNA and RNA |List the following characteristics of DNA and then write the |

|RNA is a single strand |characteristics of RNA and note comparisons among the two. |

|The sugar in RNA is called Ribose instead of DNA’s Deoxyribose | |

|Like DNA, RNA has 4 nitrogenous bases, but instead of Thymine, Uracil |(Sample of what this may look like) |

|is the 4th base |DNA |

| |RNA |

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| |Double helix |

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| |Sugar is called Deoxyribose |

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| |Bases are T, A, C, and G |

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|C52 | |

|RNA as a Single Strand |Single stranded molecule |

|You recall that DNA looks like a twisted ladder and is referred to as |Sugar is Ribose |

|a double helix | |

|RNA looks like half a ladder | |

|There is only one side to RNA |Uracil replaces thymine |

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| |C52. PPT Slide 52 |

| |[pic] |

|C53 | |

|RNA Contains Ribose |C53. PPT Slide 53 |

|Remember how DNA got its name? | |

|It is a nucleic acid with deoxyribose as the sugar on the backbone | |

|Hence the name Deoxyribonucleic acid | |

|Ribonucleic acid (RNA) has the sugar ribose on it’s backbone | |

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|C54 | |

|RNA Has Uracil | |

|Remember the base pairs in DNA? | |

|Adenine pairs with Thymine | |

|Guanine pairs with Cytosine | |

| |C54. PPT Slide 54 |

| |[pic] |

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|C55 | |

|RNA Has Uracil |C55. PPT Slide 55 |

|In RNA | |

|Adenine pairs with URACIL | |

|Guanine pairs with Cytosine | |

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|C56 | |

|Making Protein |C56. PPT Slide 56 |

|Protein production starts with DNA | |

|DNA passes instruction to RNA | |

|RNA carries out the work of linking together chains of amino acids | |

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|C57 | |

|Three Types of RNA | |

|There are three types of RNA involved in Protein Synthesis | |

|Messenger RNA (mRNA) |C57. PPT Slide 57 |

|Ribosomal RNA (rRNA) |You may give the types of RNA names for the “story” given below at |

|Transfer RNA (tRNA) |slide 61. |

| |DNA = Deena |

|C58 |mRNA = Myrna |

|Messenger RNA |tRNA = Trina |

|Messenger RNA (mRNA), brings instructions from DNA in the nucleus to | |

|the cell’s factory floor, the cytoplasm | |

|On the factory floor, mRNA moves to the assembly line, a ribosome | |

|Remember that a ribosome is either a free-floating small dot in the |C58. PPT Slide 58 |

|cell or is attached to the endoplasmic reticulum making it “rough” ER | |

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|C59 | |

|Ribosomal RNA | |

|The ribosome, made of Ribosomal RNA (rRNA) binds to the mRNA and uses | |

|the instructions to assemble the amino acids in the correct order | |

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|C60 | |

|Transfer RNA | |

|Transfer RNA (tRNA) is the supplier | |

|Transfer RNA delivers the amino acids to the ribosome to be assembled | |

|into a protein |C59. PPT Slide 59 |

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|C61 | |

|Transcription | |

|The production of messenger RNA (mRNA) is known as Transcription | |

|DNA acts as a template for the RNA molecule | |

|To View a Link to Transcription Animation Click Here. | |

| |C60. PPT Slide 60 |

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| |C61. PPT Slide 61 |

| |“The Protein Synthesis Story” |

| |Myrna, the messenger girl(mRNA) is at work one day and her boss Deena |

|C62 |(DNA) calls her into her office (the nucleus). Deena tells Myrna that|

|Transcription |she is going to give her a specific recipe for a new protein needed |

|The main difference between DNA Replication and transcription is that |elsewhere in the city (the organism). She gives her the “secret” |

|transcription results in one single strand of RNA rather than an exact|recipe code and Myrna writes it down. (This is known as |

|duplicate of a double stranded DNA molecule |transcription). |

|Much of the information on the mRNA strand codes for specific amino |(This occurs when the DNA molecule is unzipped like in replication, |

|acids to make protein |except the free floating nucleotides that fill in on the DNA molecule |

| |are RNA nucleotides and when it releases itself from the DNA the |

|C63 |resulting product is a single stranded mRNA molecule) |

|The Genetic Code |(Story continued on slide 69) |

|A code is necessary to turn the language of RNA into the language of | |

|amino acids and proteins |C62. PPT Slide 62 |

|The four nitrogenous bases make up the code | |

|The code letters are A, G, T, and C | |

|A set of three letters makes a “word” called a Codon | |

|There are 64 possible codons | |

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|C64 | |

|Codon |C63. PPT Slide 63 |

|[pic] | |

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|C65 | |

|Amino Acids | |

|There are 20 different amino acids that make up proteins | |

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|C66 | |

|The Genetic Code | |

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|C67 | |

|The Genetic Code | |

|As you could see on the chart of amino acids, there are more than one | |

|codon that code for certain amino acids | |

|This results in fewer errors in protein synthesis |C64. PPT Slide 64 |

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|C68 | |

|The Genetic Code | |

|All organisms use the same genetic code | |

|This provides evidence that all life on earth may have evolved from | |

|the same origin | |

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|C69 | |

|Ribosomes | |

|The newly produced strand of mRNA travels from the nucleus to the | |

|cytoplasm where it attaches to a ribosome |C65. PPT Slide 65 |

|The ribosome is the actual site for protein synthesis | |

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|C70 | |

|Translation: From mRNA to Protein | |

|The process of “reading” the three letter “words” , or codons, is |C66. PPT Slide 66 |

|known as translation |Take time to briefly discuss the 20 different amino acids and the |

|Translation takes place at the ribosomes in the cytoplasm |codons that code for them at the side of each one. |

|The amino acids are free-floating in the cytoplasm and congregate at | |

|the ribosome during protein synthesis |C67. PPT Slide 67 |

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|C71 | |

|The Process of Protein Synthesis | |

|The first codon is usually A-U-G, methionine, which starts the | |

|production of a new protein | |

|Following the start codon, the remaining codons call for amino acids | |

|in the order in which they appear on the mRNA strand |C68. PPT Slide 68 |

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|C72 | |

|Transfer RNA (tRNA) | |

|At the ribosome, Transfer RNA (tRNA) identifies the code through | |

|translation and finds the appropriate amino acid matching the codons | |

|Each tRNA molecule only attaches to one specific amino acid | |

|The Anticodon on the bottom of the tRNA molecule corresponds with the |C69. PPT Slide 69 |

|codons on the mRNA strand |“Protein story continued” |

| |Remember that Myrna got the secret recipe for a specific type of |

| |protein? Now Myrna leaves the office (Nucleus) and goes into the |

| |cytoplasm to find a ribosome (where the protein is made). |

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| |C70. PPT Slide 70 |

| |“Protein story continued” |

| |Myrna is now at the ribosome where the protein will be created. She |

|C73 |finds Trina (tRNA), who is the “cook” who puts the ingredients |

|Protein Synthesis Animation |together, and gives the secret protein recipe code from Deena, the |

|Click Here to Link to An Animation |boss. Trina then translates the code using a special tool called |

| |anticodons. (This process is called translation) |

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|Assessment | |

|Assess students understanding of DNA |C71. PPT Slide 71 |

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| |C72. PPT Slide 72 |

| |[pic] |

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| |“Protein story continued” |

| |Trina, who has the recipe now and has translated the code using |

| |anticodons, starts taking ingredients (amino acids) off of the shelf |

| |and chaining them together at the ribosome to produce the final |

| |product, the protein molecule. |

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| |C73. PPT Slide 73 |

| |This link will show an animation of the process of protein synthesis |

| |and should give students a good review of the process. |

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| |Sample Test |

| |Click here to link to a sample DNA test |

-----------------------

What is DNA?

What is DNA made of and what does it look like?

How can people benefit from understanding the structure of a DNA molecule? (Understanding the structure of a DNA molecule can help us understand genetic disorders, solve crimes, paternity testing, genetic engineering, cloning, etc.)

Why is DNA replication necessary in living organisms?

What have you eaten today that contained a lot of protein?

Why should you eat protein?

Where does protein come from?

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