introduction to dna structure. vocabulary dna (deoxyribonucleic acid) – a nucleic acid that...
TRANSCRIPT
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.