Inquiry: How is DNA used to store and transmit cell

information?

Essential Question #1: Compare the structures of DNA and RNA.

Essential Question #2:

Compare the functions of DNA and RNA.

Relationship Between Chromosomes and Cell 

DNA

• Double helix (twisted ladder)• Bases joined by hydrogen

bonds (A-T and C-G)– A=Adenine – T=Thymine– C=Cytosine– G=Guanine

(Bases spell a code for life)• Composed of Nucleotides

Nucleotide = deoxyribose sugar, phosphate, & base

What does DNA do?

• Contains recipe for making proteins• Gives us our inherited characteristics

– Replication - DNA copies itself exactly for cell division

DNA Models1. Color the DNA nucleotides • Use the color codes below

– Cytosine – green– Guanine – blue– Adenine – red

– Thymine – purple– Sugar – whiteSugar – white

– Phosphate – yellowPhosphate – yellow

2. Cut out the DNA nucleotides • Just like assembling a puzzle, put the nucleotides

together randomly to create DNA. Words will be upside down on one side.

3. Tape it together but DO NOT TAPE ACROSS THE BASES (ACTG) in the middle

DNA Replication

• DNA is unique among all known molecules because it is the only one that is capable of duplicating itself.

• The process of duplication is called replication. • During replication, the two complementary strands

which form the DNA molecule unzip and then are used as templates from which new strands are made as free nucleotides combine with their complementary bases.

• The result is one side of each new DNA strand is "old" and the other side is "new".

Why does this happen?

Enzymes that make DNA Replication possible

• Helicase – helps unzip the DNA molecule by breaking the hydrogen bonds between base pairs

• DNA Polymerase – reconnects the free nucleotides with the original DNA strand

How DNA Replication Works

Animation

DNA Replication Models

• Using your DNA model that you and your partner(s) constructed, cut the last 3 DNA bases where the hydrogen bonds exist.

• Slightly pull your newly separated sections of DNA apart. Determine which bases will be able to reattach to the last 3 nucleotide bases. Fill in the diagram below.

• Color and cut out the new complementary free nucleotides.

• Attach the new complementary free nucleotides to your DNA models to show how replication will occur. Use the figure below as a hint.

Summary of DNA Replication

• DNA is unzipped or unwinds.• The unwinding of the helix is facilitated by an

enzyme called helicase • Complementary bases from free nucleotides are

paired up with their match.• DNA polymerase is another enzyme that

reconnects the bases of the two new DNA strands

• DNA replication occurs to create a copy of DNA before cell reproduction.

Describe what is happening in the

picture?

What is this process called?

http://present.smith.udel.edu/biotech/rDNA.html

SB2. Students will analyze how biological SB2. Students will analyze how biological traits are passed on to successive traits are passed on to successive

generations.generations.a. Distinguish between DNA and RNA.a. Distinguish between DNA and RNA.

Comparing/Contrasting DNA/RNA

1. The sugar in the RNA molecule is ribose. DNA's sugar is deoxyribose.

2. RNA is usually a single stranded molecule while DNA is nearly always double stranded.

3. DNA's rigid double helix structure allows for only one function (information storage) whereas RNA's greater molecular diversity results in a wider range of functions

4. RNA uses the nucleotide uracil instead of thymine 5. DNA is larger than RNA 6. RNA is much less stable than DNA. As a single

stranded molecule it has no way of repairing itself

Use a Venn chart to compare DNA and

RNA

What is Transcription?

• Making a copy of the information in DNA as a new version called RNA

• When transcription is finished, the portion of the DNA that coded for a protein, i.e. a gene, is now represented by a messenger RNA molecule

• This mRNA can be used as a template for translation later.

How Transcription Works

• DNA unzips and RNA polymerase (enzyme) binds to one strand of DNA

• A chain of RNA nucleotides is created as each new RNA nucleotide complementary to the DNA nucleotide it is hydrogen bonded to.

• The completed mRNA molecule is released from RNA polymerase .

Transcription Models

• With your DNA model in front of you, demonstrate the process of transcription.– Fold the DNA model where the base pairs

touch– Match up the complementary pieces of the

RNA nucleotides from• A-U• C-G• T-A

Transcription Models

• Color the RNA nucleotides

• Use the color codes below– Cytosine – green– Guanine – blue– Adenine – red

– Uracil – light purple or pink– Sugar – whiteSugar – white

– Phosphate – yellowPhosphate – yellow

Transcription Models

• Cut out the RNA nucleotides

• Tape these nucleotides together as a new molecule. DO NOT ATTACH TO THE ORIGINAL DNA MODEL.

• What process can occur next?

Modeling Review

What is Translation?

• DNA translation is the process that converts an mRNA sequence into a string of amino acids that form a protein.

• This fundamental process is responsible for creating the proteins that make up most cells.

• It also marks the final step in the journey from DNA sequence to a functional protein.

TranslationRNA Proteins

• Look at your new RNA molecule that was created using information that was stored and transmitted from DNA.

• Fill in the letters that represent the bases in YOUR DNA model.

• Next, fill in the letters of the bases that are in YOUR RNA model.

• Starting at the top of YOUR DNA model circle every three letters as a DNA base sequence.

• Write these 3 DNA letters in the first column of your table

Example

Starting at the top of YOUR RNA model circle every three letters as a codon.

Write these 3 RNA letters in the first column of your table

Example

Identify the Amino Acid with Table 11-2

Anticodons

• Identify the tRNA anticodon from the mRNA codon

• Fill in the anti codon in the table and in the blanks on your tRNA cut out and label the amino acid that it will be bring to mRNA

• Attach this tRNA cutout to YOUR RNA strand

Example

Modeling Review