Hemophilia-

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Hemophilia-

• Caused by a defect in a single gene cannot
  produce all the proteins necessary for blood
  clotting
• Depend on expensive injections of clotting
  proteins to prevent uncontrolled bleeding

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nuclear pore
chromatin (DNA)
nucleus
nucleolus
nuclear envelope
flagellum
intermediate filaments
cytoplasm
plasma membrane
rough endoplasmic reticulum
ribosome
lysosome
microtubules
smooth endoplasmic reticulum
Golgi complex
free ribosome
vesicle
mitochondrion
vesicle
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Protein Synthesis

• Gene
• Expression

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DNA, Genes Proteins

• The relationship of Chromosomes,
• Genes, DNA Proteins

• Franklin's Legacy PBS
• DNA to Protein

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Genes and Proteins

• Genes provide information to make proteins
• Genetic information for protein synthesis is
  carried by RNA (ribonucleic acid) intermediates

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The genetic code and codons

• A sequence of nucleotide bases in DNA is
  translated into a sequence of amino acids in a
  protein.

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Protein Synthesis Two-step process

• Transcription and Translation
• Transcriptionnucleotide message sent from
  nucleus to cytoplasm
• DNA nucleotide sequence "copied" (using
  complementary base pairing) as a "messenger"
  nucleotide sequence of RNA (mRNA)

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gene 3
gene 1
DNA
gene 2
(nucleus)
(cytoplasm)
Transcription of gene 1 produces an mRNA with a
nucleotide sequence complementary to one of
the DNA strands.
(a) TRANSCRIPTION
messenger RNA
protein
(b) TRANSLATION
Translation produces a protein molecule with an
amino acid sequence determined by the
nucleotide sequence in the mRNA.
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Protein Synthesis

• 1. Transcription
• b. RNA polymerase catalyzes synthesis of mRNA
  similar to DNA replication and DNA polymerase
• Promoter sequence binds RNA polymerase
• Termination signal is a sequence of nucleotides
  at end of genes that tell RNA polymerase to stop
  transcription

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gene 3
gene 1
DNA
gene 2
(nucleus)
(cytoplasm)
Transcription of gene 1 produces an mRNA with a
nucleotide sequence complementary to one of
the DNA strands.
(a) TRANSCRIPTION
messenger RNA
protein
(b) TRANSLATION
Translation produces a protein molecule with an
amino acid sequence determined by the
nucleotide sequence in the mRNA.
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Protein Synthesis

• 1. Transcription
• c. The entire DNA molecule in a chromosome is
  not transcribed, only a specific gene or family
  of genes is transcribed

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chromosome
DNA
gene 1
gene 2
gene 3
(a) initiation
template strand
RNA polymerase
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(b) elongation
RNA
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direction of transcription
beginning of gene
growing RNA molecules
RNA polymerase
DNA
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(No Transcript)
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(a)
RNA polymerase
termination signal
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(b)
RNA
Initiation, Elongation and Termination
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gene 3
gene 1
DNA
gene 2
(nucleus)
(cytoplasm)
Transcription of gene 1 produces an mRNA with a
nucleotide sequence complementary to one of
the DNA strands.
(a) TRANSCRIPTION
messenger RNA
protein
(b) TRANSLATION
Translation produces a protein molecule with an
amino acid sequence determined by the
nucleotide sequence in the mRNA.
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Protein Synthesis

• 2. Translationnucleotide sequence of mRNA used
  to synthesize a sequence of amino acids
  (polypeptide or protein)
• a. Occurs on the endoplasmic reticulum using
  ribosomes

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rough endoplasmic reticulum
ribosomes
0.5 micrometers
smooth endoplasmic reticulum
0.5 micrometers
vesicles
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Protein Synthesis

• 2. Translation
• b. mRNA codons are used to specify amino acids
• c. Ribosomes "read" mRNA codons to synthesize a
  specific amino acid sequence

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(a) messenger RNA
A Codon three nucleotide bases
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(b)
ribosome (contains ribosomal RNA)
catalytic site
large subunit
tRNA/amino acid binding sites
small subunit
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Protein Synthesis

• 2. Translation
• d. Each of the 20 amino acids has a specific
  "carrier" transfer RNA (tRNA) that brings the
  amino acid to the ribosome
• e. Complementary base pairing between the mRNA
  and tRNAs determines the amino acid sequence

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(c) transfer RNA
attached amino acid
anticodon
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(a) messenger RNA
(b)
ribosome (contains ribosomal RNA)
catalytic site
large subunit
tRNA/amino acid binding sites
small subunit
(c) transfer RNA
attached amino acid
anticodon
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Protein Synthesis

• 2. Translation
• f. Ribosomes need to recognize the beginning and
  end of the mRNA message
• 1) Initiation (start) codon AUG (methionine)
• 2) Stop codons UAA, UAG, UGA

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amino acid
methionine tRNA
initiation complex
small ribosomal subunit
(a)
A tRNA with an attached methionine amino acid
binds to small ribosomal subunit, forming an
initiation complex.
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tRNA
mRNA
(b)
The initiation complex binds to the end of an
mRNA and travels along the mRNA until it
encounters an AUG codon. The anticodon of the
tRNA pairs with the AUG codon.
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second binding site
catalytic site
large ribosomal subunit
first binding site
(c)
The large ribosomal subunit binds to the small
subunit, with the mRNA between the two
subunits. The methionine tRNA is in the
first binding site on the large subunit.
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catalyic site
(d)
A second tRNA enters the second binding site.
Its anticodon pairs with the codon in the mRNA.
The tRNA carries an attached amino acid.
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peptide bond
(e)
The catalytic site catalyzes the formation of a
peptide bond that links the two amino acids. Both
amino acids are now attached to the tRNA in the
second binding position.
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catalytic site
tRNA detaches
ribosome moves one codon to right
(f)
The empty tRNA is released and the ribosome
moves one codon to the right. The tRNA with the
two amino acids is now in the first tRNA
binding site. The second tRNA binding site is
empty.
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catalytic site
(g)
Another tRNA, with an anticodon complementary to
the next mRNA codon, enters the second
binding site. This tRNA carries the next amino
acid to be added to the chain.
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(h)
The catalytic site forms a peptide bond that
attaches the new amino acid at the end of the
chain. The chain of three amino acids is now
attached to the tRNA in the second binding site.
The empty tRNA in the first site will be
released and the ribosome will move one codon to
the right.
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completed peptide
stop codon
(i)
Binding of tRNAs and formation of peptide bonds
between amino acids continues until the ribosomes
reaches a stop codon. No tRNA binds to
stop codons. Instead, protein release factors
signal the ribosome to release the newly made
protein. The mRNA is also released, and the
subunits separate.
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second binding site
large ribosomal subunit
amino acid
catalytic site
methionine tRNA
tRNA
initiation complex
first binding site
mRNA
small ribosomal subunit
(a)
(b)
(c)
catalytic site
tRNA detaches
catalytic site
peptide bond
ribosome moves one codon to the right
(f)
(d)
(e)
catalytic site
completed peptide
stop condon
(g)
(h)
(i)
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gene
gene in DNA (template strand)
(a)
codon
mRNA (codons)
(b)
anticodon
(c)
tRNA (anticodons)
amino acids
(d)
protein (amino acids)
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Review Protein Synthesis

• Two Major Steps of Protein Synthesis
  Transcription Translation
• Initiation, Elongation and Termination