Introduction to DNA

Structure

VocabularyDNA (Deoxyribonucleic Acid) – A

nucleic acid that contains a deoxyribose sugar. Is a long molecule that is made up of units called nucleotides

Nucleotides – Monomer of nucleic acids made up of a 5-carbon sugar, a phosphate group, and a nitrogenous base. The THREE basic units of DNA

DNA

DNA contains the genetic code of an organism, with traits expressed through proteins made by cells

DNA can be found in the nucleus and mitochondria.

2 rings 1 ring

Double Helix

DNA resembles a twisted ladder, with sugars and phosphates on sides, and nitrogen bases as rungs

5’ has a free Phosphate3’ end has a free Sugar

Nitrogen BasesThe nitrogen bases of DNA from

complementary base pairs with adenine pairing with thymine, and cytosine pairing with guanine

The nitrogen bases spell out a coded message.

Quiz: DNA1. Name the three parts of a

nucleotide.

2. Find the complimentary strand for the following DNA strand:

ATTTCGTGCAGA

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3. Do purines of pyrimidines have two rings?

4. What does a double helix look like?

5. What does DNA stand for?a) Degraded Nucleic Acid

b) Deoxyribose Nitrogenous Acid

c) Deoxyribonucleic acid

6. What was Rosaline Franklin known for?

Finding out the structure of DNA Taking pictures of DNA with a x-

ray Discovering the existence of DNA

7. What are Watson and Crick known for?

a) Finding out the structure of DNA

b) Taking pictures of DNA with a x-ray

c) Discovering the existence of DNA

Introductions to DNA

Replication

Replication

DNA replication happens in the Synthesis phase of the cell cycle

Happens BEFORE mitosis

Replication

DNA Replication

When DNA is replicated or copied, it results in two IDENTICAL strands.

Replication happens in three simple steps:

1. The two original strands of DNA are separated by helicase

1. DNA Polymerase adds complimentary nucleotides to each strand.

1. Two DNA molecules form that are identical to the original.

Step 1: DNA Separates

The DNA helix unwinds with the help of enzymes called DNA helicases.

Nucleotide bases separate at an area called the replication fork.

Step 2: DNA Polymerase adds nucleotides

At the replication fork, DNA Polymerase move along each DNA strand and add complimentary nucleotides.Adenine with thymineCytosine with Guanine

Two new strands begin to form.

NewStrandsforming

Step 3: Two DNA Molecules formDNA polymerase continues adding nucleotides

until all the DNA has been copied.DNA polymerase detaches and two new

identical DNA molecules are left.

DNA Polymerases other role…

Because errors can occur in DNA replication, DNA polymerase also has a role in fixing the new DNA strands.

DNA polymerase fix mismatched nucleotides

DNA Replication in Eukaryotes

Eukaryotes have one long DNA strand for each chromosome

semi conservative model (new double helix has 1 parent strand + 1 new daughter strand)

replication fork

Parent strand

Daughter strand

DNA REPLICATION in Prokaryotes

Prokaryotes have one circular DNA

replication fork

PASTA DNA LAB

1. Follow Procedure I to make a model of DNA.

Follow the directions EXACTLY the same EXCEPT instead of tying the noodles on string, GLUE THEM on to notebook paper.

2. In Procedure two, make a model of DNA “unzipping” or separating on another piece of paper.

3. The show 2 identical DNA strands that were made.

They should look EXACTLY like the first DNA strand.

Pasta DNA

Wheels- SugarNoodle-PhosphatePaper clip- Bases

From DNA to Protein

Transcription

Making Proteins……involves a

series of steps.Transcription &

Translation

mRNA is made in transcription.

Protein is made in translation.

RNARNA differs from

DNA in three ways:Single strandedHas uracil instead

of thymine nitrogen bases

Contains ribose sugar instead of deoxyribose in its backbone.

Transcription in 3 easy stepsStep 1

Transcription starts when RNA polymerase binds to a specific DNA sequence that tells cell to START transcription.Remember, A,T,C, and G “spell” out messages.

START

Step 2

Next, the RNA polymerase unwinds and separates the DNA.

Step 3Last, RNA polymerase adds complimentary

RNA nucleotides to the DNA strand. The polymerase adds:

cytosine to guanine and guanine to cytosine

adenine to thymine BUT uracil to adenine.

Why make Messenger RNA?

When a cell needs a protein, mRNA is created.

mRNA carries instructions for building a protein and delivers it out side of the nucleus.

ACTIVITY! ^_^ Your objective is to take the following DNA strands and transcribe them into RNA. Materials: Pipe cleaners and colored beads.

Green: Adenine; Yellow: Guanine; Red: Thymine; Blue: Cytosine; WhiteWhite: Uracil. Procedure: Transcribe the SECOND STRAND of each of the following DNA

sequences. Make your DNA and RNA using the pipe cleaner given and the colored beads. Show me your RNA strand. If it is correct then turn into me your RNA sequences

written down on paper. Return the beads and pipe cleaners

DNA sequence oneStrand one: ATGCTGAAGStrand two: TACGACTTC

DNA sequence threeStrand one: TATCGTAGTStrand two: ATAGCATCA

DNA sequence twoStrand one: CGCTTAAACStrand two: GCGAATTTG

DNA sequence fourStrand one: ATGCAATAGStrand two: TACGTTATC

From DNA to Protein

Translation

Vocabulary

Ribosomal RNA are part of the structure of ribosomes. They hold the mRNA and

two tRNAs in place during translation

tRNA molecules are single strands of RNA that carry a specific amino acid with them.

Amino acids: make PROTEINS

Vocabulary

Codons: instructions written as three nucleotide sequences. Each codon

corresponds to an amino acid or start or stop signal.

Ex:GUA ValineUUC Phenylalanine

To build a protein…

…we must move on to our next step that moves our RNA out of the nucleus and into the cytoplasm.

Translation

mRNA moves into the cytoplasm where it binds with a rRNA, and a tRNA carrying an amino acid.

The codon is ready to receive the next tRNA and its amino acid

Once mRNA is holding two tRNAs, each carrying specific amino acids, enzymes form peptide bonds between the two amino acids.

The tRNA in the first site prepares to detach, leaving behind the amino acid.

Peptidebond

Another tRNA fills in the empty site.This process repeats until a STOP codon is

reached (UAG, UAA, or UGA).The amino acid chain is release, forming into a

new protein.

Transcription

Amino acids form protein.