From Gene to Protein

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From Gene to Protein
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Target

• I can label a diagram of a DNA molecule including
  structural elements and bonds between strands.

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Target

• I can describe the primary function of DNA.

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Human Genome

• 3.2 million DNA base pairs
• 1.5 encode proteins
• 98.5 not protein encoding
• 31,000 genes encoding 100,000 - 200,000
  proteins
• How are 100,000 to 200,000 proteins produced from
  31,000 genes?
• What is the 98.5 of the human genome that does
  not encode proteins?

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Proteins are worker molecules that are necessary
for virtually every activity in your body
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Targets

• I can differentiate between transcription and
  translation.
• I can locate within the cell and describe the
  steps of protein synthesis.

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The Central Dogma

• Flow of genetic information in a cell
• How do we move information from DNA to proteins?

transcription
translation
protein
RNA
DNA
trait
DNA gets all the glory, but proteins do all
the work!
replication
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Transcription

• fromDNA nucleic acid languagetoRNA nucleic
  acid language

Animation!
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RNA

• ribose sugar
• N-bases
• uracil instead of thymine
• U A
• C G
• single stranded
• lots of RNAs
• mRNA, tRNA, rRNA, siRNA

transcription
RNA
DNA
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Transcription

• Making mRNA
• transcribed DNA strand template strand
• synthesis of complementary RNA strand
• transcription bubble
• enzyme
• RNA polymerase

coding strand
3?
C
C
G
G
A
A
T
T
5?
A
G
A
A
A
C
G
T
T
T
T
C
A
T
C
G
C
A
T
DNA
3?
C
T
G
A
A
5?
T
G
C
C
G
G
A
U
U
T
C
unwinding
3?
C
G
G
A
A
T
rewinding
mRNA
template strand
RNA polymerase
5?
build RNA 5??3?
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Matching bases of DNA RNA
A

• Match RNA bases to DNA bases on one of the DNA
  strands

C
U
G
A
G
G
U
C
U
U
G
C
A
C
A
U
A
G
A
C
U
A
5'
3'
G
A
C
C
A
G
G
G
G
G
G
T
T
A
C
A
C
T
T
T
T
T
C
C
C
C
A
A
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Transcription the process

• 1.Initiation proteins help RNA polymerase bind
  to the right spot of the DNA
• 2.Elongation RNA polymerase continues unwinding
  DNA and adding nucleotides
• 3.Termination RNA polymerase reaches terminator
  sequence

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Eukaryotic genes have junk!

• Eukaryotic genes are not continuous
• exons the real gene
• expressed / coding DNA
• introns the junk
• inbetween sequence

intronscome out!
eukaryotic DNA
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mRNA splicing
Video

• Post-transcriptional processing
• eukaryotic mRNA needs work after transcription
• primary transcript pre-mRNA
• mRNA splicing
• edit out introns
• make mature mRNA transcript

10,000 bases
eukaryotic DNA
pre-mRNA
primary mRNA transcript
1,000 bases
mature mRNA transcript
spliced mRNA
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Translation

• fromnucleic acid languagetoamino acid language

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How does mRNA code for proteins?
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ATCG
4
AUCG
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• How can you code for 20 amino acids with only 4
  nucleotide bases (A,U,G,C)?

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mRNA codes for proteins in triplets
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The code

• Code for ALL life!
• strongest support for a common origin for all
  life
• Code is redundant
• several codons for each amino acid
• 3rd base wobble

Why is thewobble good?

• Start codon
• AUG
• methionine
• Stop codons
• UGA, UAA, UAG

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How are the codons matched to amino acids?
TACGCACATTTACGTACGCGG
DNA
AUGCGUGUAAAUGCAUGCGCC
mRNA
codon
anti-codon
tRNA
aminoacid
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Transfer RNA structure

• Clover leaf structure
• anticodon on clover leaf end
• amino acid attached on opposite end

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Ribosomes

• Facilitate coupling of tRNA anticodon to mRNA
  codon
• Structure
• ribosomal RNA (rRNA) proteins
• 2 subunits
• large
• small

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Translation

• Initiation
• brings together mRNA, ribosome subunits, first
  tRNA
• Elongation
• adding amino acids based on codon sequence
• Termination
• end codon

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A small ribosomal subunit attaches to a mRNA
molecule. At the same time an initiator tRNA
molecule binds to AUG on the same mRNA molecule.
A large ribosomal subunit then joins the newly
formed complex (not shown). 
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Small ribosomal subunit
As the ribosome moves along the mRNA molecule,
the first tRNA is released leaving behind its
amino acid. Another tRNA that recognizes the new
mRNA codon takes the open position.
Large ribosomal subunit
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As the ribosome moves along the mRNA molecule,
the first tRNA is released leaving behind its
amino acid. Another tRNA that recognizes the new
mRNA codon takes the open position.
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This pattern continues as molecules of tRNA are
released from the complex, new tRNA molecules
attach, and the amino acid chain grows.
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This pattern continues as molecules of tRNA are
released from the complex, new tRNA molecules
attach, and the amino acid chain grows.
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This pattern continues as molecules of tRNA are
released from the complex, new tRNA molecules
attach, and the amino acid chain grows.
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The ribosome will translate the mRNA molecule
until it reaches a termination codon on the mRNA. 
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The ribosome will translate the mRNA molecule
until it reaches a termination codon on the mRNA. 
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The ribosome will translate the mRNA molecule
until it reaches a termination codon on the mRNA. 
Animation!
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