Transcript Protein Synthesis

Protein Synthesis
Transcription and Translation
DNA
Transcription
RNA
Translation
Protein
RNA
• Structure: nucleic acid made up of repeating nucleotides
similar to DNA
• Consists of ribose sugar, nitrogenous base, and a
phosphate group
TYPES OF RNA
– Messenger RNA (mRNA): single uncoiled chain;
mRNA carries genetic information from the nucleus to
the cytosol
– Transfer RNA (tRNA): about 80 RNA
nucleotides folded into a hairpin shape;
binds to specific amino acids
– Ribosomal RNA (rRNA): RNA nucleotides in a
globular form; rRNA makes up the ribosomes where
proteins are made
TRANSCRIPTION
• Process in which genetic information is
copied from DNA to RNA and is called
mRNA
• RNA carries the genetic information from
the DNA in the nucleus to the cytosol
• This way the information can be used to
make proteins
TRANSCRIPTION
• RNA polymerase synthesizes RNA
copies of specific sequences of DNA
– RNA polymerase: the primary
transcription enzyme
• RNA polymerase initiates
transcription by binding to specific
regions of DNA (promoters)
• Promoters: specific regions of DNA
that mark the beginning of
transcription in the chain, RNA
polymerase binds to these
promoters
• DNA molecule in the region
separates when RNA polymerase
binds
• Template: separated DNA chain
used for transcription
• RNA polymerase adds
complementary RNA nucleotides to
the newly forming RNA molecule
(uses complementary base pairing)
TRANSCRIPTION
• Transcription continues until the
termination signal: a specific sequence of
nucleotides that signifies the end of a gene
• RNA polymerase releases both the DNA
molecule and newly formed RNA molecule
• All three types of RNA are involved in protein
synthesis
• mRNA leaves the nucleus and moves into the
cytosol to direct protein synthesis
TRANSLATION
• Process of assembling polypeptides from
information encoded in mRNA by codons
• Codon: a combination of three mRNA
nucleotides that code for a specific amino
acid
– Some codons code for translation to start and
stop
• Start codon (AUG) codes for methionine
• Stop codon (UAA, UAG, UGA) causes translation
to stop
TRANSLATION
• When mRNA leaves the nucleus, it migrates to a
ribosome in the cytosol (this is the site of protein
synthesis)
• tRNA transports amino acids to the ribosomes
• tRNA has a region that bonds to a specific amino
acid and on the opposite end, it has an
anticodon
• Anticodon: three nucleotides that is
complimentary to and pairs with its mRNA codon
• Ribosomes are composed of rRNA and proteins
PROTEINS
• Proteins: polymers, made up of one or
more polypeptides
• Polypeptides: amino acids linked by
peptide bonds
• Sequence of amino acids determines the
shape of the protein
• The shape (3-D structure) determines the
function of the protein
Protein Assembly
• http://nobelprize.org/educational_games/m
edicine/dna/b/translation/translation_ani.ht
ml
• http://highered.mcgrawhill.com/sites/0072437316/student_view0/
chapter15/animations.html#
• http://learn.genetics.utah.edu/content/begi
n/dna/transcribe/