hemophilia- 1. caused by a defect in a single gene cannot produce all the proteins necessary for...
TRANSCRIPT
Hemophilia-
1. Caused by a defect in a single gene cannot produce all the proteins necessary for blood clotting
2. Depend on expensive injections of clotting proteins to prevent uncontrolled bleeding
flagellum
cytoplasmrough endoplasmicreticulum
ribosome
microtubules
lysosome
mitochondrion
Golgi complex
plasmamembrane
intermediatefilaments
vesicle
smooth endoplasmicreticulum
free ribosomevesicle
nuclear porechromatin (DNA)
nucleolusnuclear envelope
nucleus
Protein Synthesis
Gene
Expression
DNA, Genes & Proteins
The relationship of Chromosomes,
Genes, DNA & Proteins
Franklin's Legacy | PBSDNA to Protein
Genes and Proteins
Genes provide information to make proteins
Genetic information for protein synthesis is carried by RNA (ribonucleic acid) intermediates
The genetic code and codons
A sequence of nucleotide bases in DNA is translated into a sequence of amino acids in a protein.
Protein Synthesis Two-step process
Transcription and Translation 1. Transcription—nucleotide message sent from
nucleus to cytoplasm
a. DNA nucleotide sequence "copied" (using complementary base pairing) as a "messenger" nucleotide sequence of RNA (mRNA)
Transcription ofgene 1 produces an mRNA with a nucleotide sequence complementary to one of the DNA strands.
Translation produces a protein molecule with an amino acid sequence determined by the nucleotide sequence in the mRNA.
(a) TRANSCRIPTION
(b) TRANSLATION
messenger RNA
gene 1gene 3
gene 2
DNA
(nucleus)
protein
(cytoplasm)
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
Transcription ofgene 1 produces an mRNA with a nucleotide sequence complementary to one of the DNA strands.
Translation produces a protein molecule with an amino acid sequence determined by the nucleotide sequence in the mRNA.
(a) TRANSCRIPTION
(b) TRANSLATION
messenger RNA
gene 1gene 3
gene 2
DNA
(nucleus)
protein
(cytoplasm)
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
(a) initiation
RNA polymerase
gene 1 gene 3gene 2
DNA
template strand
chromosome
(b) elongation
RNA
direction of transcription
RNA polymerase
DNA
beginningof gene
growingRNA
molecules
(a)
RNA polymerase
terminationsignal
RNA
(b)
Initiation, Elongation and Termination
Transcription ofgene 1 produces an mRNA with a nucleotide sequence complementary to one of the DNA strands.
Translation produces a protein molecule with an amino acid sequence determined by the nucleotide sequence in the mRNA.
(a) TRANSCRIPTION
(b) TRANSLATION
messenger RNA
gene 1gene 3
gene 2
DNA
(nucleus)
protein
(cytoplasm)
Protein Synthesis
2. Translation—nucleotide sequence of mRNA used to synthesize a sequence of amino acids (polypeptide or protein)
a. Occurs on the endoplasmic reticulum using ribosomes
0.5 micrometers
smooth endoplasmic reticulum
vesicles
ribosomes
rough endoplasmic reticulum
0.5 micrometers
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
(a) messenger RNA
A Codon = three nucleotide bases
tRNA/amino acid binding sites
(b)catalytic site
smallsubunit
largesubunit
ribosome (containsribosomal RNA)
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
(c) transfer RNA
attachedamino acid
anticodon
(c) transfer RNA
tRNA/amino acid binding sites
(b)
(a) messenger RNA
catalytic site
attachedamino acid
smallsubunit
largesubunit
anticodon
ribosome (containsribosomal RNA)
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
amino acid
methioninetRNA
smallribosomalsubunit
initiationcomplex
A tRNA with an attached methionineamino acid binds to smallribosomal subunit, formingan initiation complex.
(a)
tRNA
mRNA
(b) The initiation complex bindsto the end of an mRNA andtravels along the mRNA untilit encounters an AUG codon.The anticodon of the tRNApairs with the AUG codon.
second binding sitecatalytic site
firstbindingsite
largeribosomalsubunit
The large ribosomal subunit bindsto the small subunit, with themRNA between the two subunits.The methionine tRNA is in the firstbinding site on the large subunit.
(c)
catalyic site
A second tRNA enters thesecond binding site. Itsanticodon pairs with the codonin the mRNA. The tRNAcarries an attached aminoacid.
(d)
peptidebond
(e) The catalytic site catalyzes the formationof a peptide bond that links the twoamino acids. Both amino acids are nowattached to the tRNA in the secondbinding position.
ribosome moves one codon to right
The “empty” tRNA is released andthe ribosome moves one codon to the right. The tRNA with the two amino acids is now in the first tRNA bindingsite. The second tRNA binding site is empty.
(f)
tRNA detaches
catalytic site
Another tRNA, with an anticodoncomplementary to the next mRNAcodon, enters the second bindingsite. This tRNA carries the nextamino acid to be added to the chain.
(g)
catalytic site
The catalytic site forms a peptidebond that attaches the new aminoacid at the end of the chain. Thechain of three amino acids is now attached to the tRNA in the secondbinding site. The empty tRNA in the first site will be released and the ribosome will move one codon to the right.
(h)
completed peptide
(i) Binding of tRNAs and formation ofpeptide bonds between amino acidscontinues until the ribosomes reachesa stop codon. No tRNA binds to stopcodons. Instead, protein “releasefactors” signal the ribosome to releasethe newly made protein. The mRNA isalso released, and the subunits separate.
stop codon
amino acid
init
iati
on
co
mp
lex
methionine tRNA
tRNA
mRNA
first binding site
large ribosomal subunit
second binding site
catalytic site
catalytic site
catalytic site
catalytic site
peptide bond
ribosome moves one codon to the right
tRNA detaches
completedpeptide
stop condon
smallribosomalsubunit
(a) (b) (c)
(d)
(g) (h)
(e) (f)
(i)
amino acids
anticodon
codon
gene in DNA(template strand)
(a)
(b)
(c)
(d)
mRNA(codons)
tRNA(anticodons)
protein(amino acids)
gene
Review Protein Synthesis
Two Major Steps of Protein Synthesis Transcription & Translation
Initiation, Elongation and Termination