Daily Entry
• What are the 4 nitrogenous bases found in
DNA?
• What are the 3 parts of a nucleotide?
• Why are the nitrogenous bases in the
double helix held together by weak bonds?
• Why and when does DNA replicate?
• What are the two main enzymes during
DNA replication and what do they do?
• Replicate this DNA strand:
AATTGCGCTATAAGC
RNA
Transcription
&
Translation
DNA vs. RNA
Structure
DNA
Double helix
Sugar = deoxyribose
RNA
Helix
Sugar = ribose
DNA vs. RNA
DNA
• Nucleotides:
1.
2.
3.
4.
Adenine (A)
Cytosine (C)
Guanine (G)
Thymine (T)
RNA
• Nucleotides:
1.
2.
3.
4.
Adenine (A)
Cytosine (C)
Guanine (G)
Uracil (U)
Types of RNA
• Messenger RNA (mRNA)
• Transfer TRNA (tRNA)
• Ribosomal RNA (rRNA)
Messenger RNA (mRNA)
Transfer RNA (tRNA)
Ribosomal RNA (rRNA)
Steps of Protein Synthesis:
DNA
mRNA
Amino acids
Protein
• Protein synthesis  to make proteins
STEP 1: RNA Helicase binds to promoter site
and separates DNA molecule.
STEP 2: RNA Polymerase adds
complementary nucleotides to RNA
Molecule.
STEP 3: RNA Polymerase reaches DNA
termination signal (marks the end of a gene).
STEP 4: RNA polymerase releases both the
DNA and RNA molecule.
• Complementary Base Pairs:
– Adenine pairs with Uracil
– Thymine pairs with Adenine
Still the Same:
– Cytosine pairs with Guanine
– Guanine pairs with Cytosine
• Transcription is used to make all three
kinds of RNA molecules.
• Once completed, the new RNA molecule
moves from the nucleus to the cytoplasm.
PRACTICE:
ACTG GTAC CTTTAC G GTCA
U G A C C A U G G AAA U G C C A G U
C G T T C AA C T G G A C C T G AAT
G C AA G U U G A C C U G G A C U U A
RNA to Amino Acids (Proteins)
outside of the nucleus
• Meet the codon…
– A codon is a grouping of three mRNA
nucleotides.
– A string of mRNA can be written as:
AUGGCUGUAAAGAGCUAG
Or it can be written to show the codons:
AUG GCU GUA AAG AGC UAG
How many codons code for three amino acids?
• There are specific codons that
can stop translation:
–
–
–
–
AUG = Start
UAA = Stop
UAG = Stop
UGA = Stop
• Steps of Translation
– Translation is the process of
assembling PROTEINS from
information encoded in mRNA.
Where does mRNA get the
genetic coding for the genes?
• Steps of Translation
– The beginning of translation is
signified when mRNA leaves the
nucleus.
• Steps of Translation
– The small unit of
the ribosome
connects with the
mRNA chain at the
AUG (start) codon.
• Steps of Translation
– Then the large
subunit connects
to the small
subunit of the
ribosome.
• Ribosomes:
– Composed of
proteins and
rRNA.
– Ribosomes can
float freely in the
cytoplasm or are
attached to…
• The codon in
mRNA pairs with
the anticodon on
the tRNA.
• Codons code for
the amino acids
that are attached to
the tRNA.
• Not anticodons
• Codon = GGU
– Anticodon = CCA
– Amino Acid = Glycine
• Codon = CCA
– Anticodon = GGU
– Amino Acid = proline
• Codon = ACG
– Anticodon = UGC
– Amino Acid =
Threonine
• Codon = AAG
– Anticodon = UUC
– Amino Acid = Lysine
• Steps of Translation
– Two tRNA
molecules bind to
mRNA and the
amino acid
molecules bond to
form a protein
chain.
Review
• DNA replication
– S phase of interphase before Mitosis
– Helicase- unwinds DNA
– Polymerase- adds nitrogenous bases to new
strand
• 1. Transcription
– DNA to mRNA in the nucleus
• 2. Translation
– mRNA to amino acids to proteins in cytoplasm
• Codons are mRNA that code for amino
acids
Videos
• http://www.youtube.com/watch?v=zdDkiR
w1PdU
• http://glencoe.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=swf::5
50::400::/sites/dl/free/0078802849/383936
/Vis_transcription_translation.swf::Visualizi
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