Download Introduction to DNA

Introduction to DNA
Structure
Vocabulary
DNA (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 Phosphate
3’ end has a free Sugar
Nitrogen Bases
The 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: DNA
1.
Name the three parts of a
nucleotide.
4. What does a double helix look
like?
5. What does DNA stand for?
a)
b)
c)
2.
Find the complimentary
strand for the following DNA
strand:
ATTTCGTGCAGA
??????????????
3. Do purines of pyrimidines have
two rings?
Degraded Nucleic Acid
Deoxyribose Nitrogenous Acid
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)
b)
c)
Finding out the structure of DNA
Taking pictures of DNA with a x-ray
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
New
Strands
forming
 At the replication fork, DNA Polymerase move along
each DNA strand and add complimentary nucleotides.
Adenine with thymine
Cytosine with Guanine
 Two new strands begin to form.
Step 3: Two DNA Molecules form
DNA 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)
Parent strand
 replication fork
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- Sugar
Noodle-Phosphate
Paper 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.
RNA
RNA differs from
DNA in three ways:
Single stranded
Has uracil instead
of thymine nitrogen
bases
Contains ribose
sugar instead of
deoxyribose in its
backbone.
Transcription in 3 easy steps
Step 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 3
Last, 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; White: 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 one
Strand one: ATGCTGAAG
Strand two: TACGACTTC
 DNA sequence three
Strand one: TATCGTAGT
Strand two: ATAGCATCA
DNA sequence two
Strand one: CGCTTAAAC
Strand two: GCGAATTTG
DNA sequence four
Strand one: ATGCAATAG
Strand 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  Valine
UUC 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
Peptide
bond
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.
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.