Transcript Protein Synthesis - Ms. Bruce's Science Classes

Review
1
Base Pairing Rule
• Watson and Crick showed that DNA
is a double helix
• A (adenine) pairs with T (thymine)
• C (cytosine) pairs with G (guanine)
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DNA
Replication
3
Steps in DNA Replication
Occurs when chromosomes duplicate
(make copies)
The enzyme DNA polymerase adds new
nucleotides
Each old strand of nucleotides serves
as a template for each new strand
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Another View of Replication
5
RNA
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RNA Differs from DNA
1. RNA has a sugar ribose
2. RNA contains the base uracil (U)
3. RNA molecule is single-stranded
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Structure of RNA
8
.
Three Types of RNA
• Messenger RNA (mRNA) carries
genetic information to the
ribosomes
• Transfer RNA (tRNA) transfers
amino acids to the ribosomes
where proteins are synthesized
• Ribosomal RNA (rRNA), along
with protein, makes up the
ribosomes
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RNA
• RNA – Ribonucleic Acid
• Single stranded nucleotide chain
– Single stranded helix
• DNA’s Thymine is REPLACED by Uracil
– A & T “break up” because of the new guy: U
– But C & G are still 4-eva
• mRNA - messenger RNA
– Used for protein synthesis
– Codes for amino acid sequence
– made from DNA
– travels
• Nucleus  Cytoplasm  Ribosomes
DNA:
GACCATAGC
mRNA: CUGGUAUCG
Codon: group of 3 bases
“GAC” or “CAT”
• tRNA – transfer RNA
– Brings specific amino acid to the
mRNA codon
growing amino acid chain
“UGG”
– “fetching puppy”
Anticodon
“ACC”
Corresponding
Amino Acid
The Genetic Code
• Use mRNA codons with chart!!!!
• DNA = AAT CCG GGG ATC ATG CCG
• mRNA
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Ribosomal RNA (rRNA)
• rRNA is a single
strand
• Globular in shape
• Site of protein
Synthesis
• “docking station”
Transfer RNA (tRNA)
• Clover-leaf shape
• Single stranded molecule folded like
a “t”
• attachment site at one end for an
amino acid
• Opposite end has three nucleotide
bases called the anticodon
Transfer RNA
anticodon
Making a
Protein
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Argenine – Leucine – Aspartic Acid
Peptide Bonds –
amino acids are
connected together
through peptide bonds
Proteins = polypeptide = amino acid
chain
Transcription
• Transcription – stage of protein
synthesis where instructions for making
a protein are transferred to an RNA
molecule
– DNA  mRNA : transcription
• Translation – stage of protein synthesis
when the information in mRNA is used
to make proteins
– mRNA  amino acid chain
Genes & Proteins
 Proteins are made of amino
acids linked together by peptide
bonds
 20 different amino acids exist
 Amino acids chains are called
polypeptides
 Segment of DNA that codes for
the amino acid sequence in a
protein are called genes
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Two Parts of Protein
Synthesis
 Transcription makes an RNA
molecule complementary to a
portion of DNA
 Translation occurs when the
sequence of bases of mRNA
DIRECTS the sequence of amino
acids in a polypeptide
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Genetic Code
 DNA contains a triplet code
 Every three bases on DNA codes
for ONE amino acid
 Each three-letter unit on mRNA is
called a codon
 Most amino acids have more than
one codon!
 There are 20 amino acids with a
possible 64 different triplets
 The code is nearly universal among
living organisms
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Always… use
mRNA to
decode!!!
Name the Amino Acids
Use the code by reading from the
center to the outside
•
•
•
•
•
GGG?
UCA?
CAU?
GCA?
AAA?
Remember the
Complementary Bases
On DNA:
A-T
C-G
On RNA:
A-U
C-G
Codons and Anticodons
• The 3 bases of an
anticodon are
complementary to
the 3 bases of a
codon
• Example: Codon ACU
Anticodon UGA
UGA
ACU
Transcription
Translation
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PROTEIN
SYNTHESIS
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Protein Synthesis
 The production (synthesis)
of polypeptide chains
(proteins)
 Two phases:
Transcription & Translation
 mRNA must be processed
before it leaves the nucleus
of eukaryotic cells
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DNA  RNA  Protein
Nuclear
membrane
DNA
Transcription
Eukaryotic
Cell
Pre-mRNA
RNA Processing
mRNA
Ribosome
Translation
Protein
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Pathway to Making a
Protein
DNA
mRNA
tRNA (ribosomes)
Protein
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