Transcript 4a. Know the general pathway by which ribosomes synthesize

4a. Know the general pathway by
which ribosomes synthesize
proteins, using tRNAs to translate
genetic information in mRNA.
Translation (RNA  Protein)
• Process of
converting
____________
in mRNA into a
sequence of
amino acids in a
protein.
Translation Steps
1. The starting end of the mRNA strand attaches to
a _________________.
2. Then, _________ molecules, each carrying a
specific amino acid, approach the ribosome.
3. When a tRNA anticodon pairs w/ the 1st mRNA
codon, the 2 molecules temporarily join
___________.
4. Usually, the 1st codon on mRNA is
________,which codes for the amino acid
methionine.
•
AUG signals the ____________ of protein synthesis.
Translation Steps
5. When the signal is given, the ribosome ____________
along the mRNA to the next codon
6. A new ________ molecule carrying an amino acid
pairs w/ the 2nd ___________ codon
7. When the 1st & 2nd amino acids are in place, an
________________ joins them by forming a peptide
bond between them.
8. As the process continues, a chain of amino acids is
formed until the ribosome reaches a _________ codon
(UAA, UAG, UGA) on the mRNA strand.
Translation
– What is translation?
– Translation is the ________ of an mRNA
message into a polypeptide chain (protein).
– _______________ takes place on ribosomes.
– During translation, the cell uses information
from _______ to produce proteins.
Translation
• Messenger RNA is
___________ in the nucleus,
and then enters the cytoplasm
where it attaches to a
Nucleus
ribosome.
mRNA
Translation
• Translation begins when an mRNA molecule
attaches to a ribosome.
• As each _________ of the mRNA molecule moves
through the ribosome, the proper amino acid is
brought into the ribosome by tRNA.
• In the ribosome, the amino acid is transferred to
the growing ______________ chain.
Translation
• Each tRNA molecule carries only one kind
of _____________ ________.
• In addition to an amino acid, each tRNA
molecule has __________ unpaired bases.
• These bases, called the ____________, are
complementary to one mRNA codon.
Translation
•The ribosome binds new ________ molecules and
amino acids as it moves along the _________.
Phenylalanine
Methionine
Ribosome
mRNA
Start codon
tRNA
Lysine
• Protein Synthesis
Translation
Lysine
tRNA
Translation direction
mRNA
Ribosome
Translation
• The process continues until the ribosome reaches a ______
_________.
Polypeptide
Ribosome
tRNA
mRNA
The Roles of RNA and DNA
• The Roles of RNA and DNA
• The cell uses the_________ “master plan” to
prepare _________ “blueprints.” The _______ stays
in the nucleus.
• The __________ molecules go to the protein
building sites in the cytoplasm—the ribosomes.
Genes and Proteins
• Genes and Proteins
• Genes contain instructions for assembling proteins.
• Many proteins are _____________, which catalyze
and regulate chemical reactions.
• Proteins are each specifically designed to build or
operate a component of a ___________ _____.
Genes and
Proteins
• The sequence of
bases in _________
is used as a
template for
mRNA.
• The codons of
_________ specify
the sequence of
amino acids in a
protein.
Codon
Codon Codon
Single strand of DNA
Codon Codon Codon
mRNA
Alanine Arginine Leucine
Amino acids within
a polypeptide
4b. Know to apply the genetic
coding rules to predict the sequence
of amino acids from a sequence of
codons in RNA.
The Genetic Code
• The nucleotide sequence
transcribed from DNA to a
strand of mRNA acts as a
genetic message, the
complete information for the
building of a protein
• _________: set of 3
nitrogen bases that
represents an amino acid
• The way that the amino
acids are placed will
determine the ___________
to be made
The Genetic Code
• The Genetic Code
• The genetic code is the “______________” of
mRNA instructions.
• The code is written using four “________” (the
bases: A, U, C, and G).
The Genetic Code
• A __________ consists of three consecutive
nucleotides on mRNA that specify a
particular amino acid.
The Genetic Code
• Each codon specifies a particular amino acid that is to be
placed on the _____________ chain.
• Some amino acids can be specified by more than one
codon.
The Genetic Code
The Genetic Code
• There is one codon AUG that can either specify the amino
acid _________________ or serve as a “________” codon
for protein synthesis.
• There are three “________________” codons that do not
code for any amino acid. These “stop” codons signify the
end of a polypeptide.
4e. Know proteins can differ from
one another in the number &
sequence of amino acids.
Protein Sequences—Hemoglobin
Protein Sequences—HIV
Wrap—Up
• Protein molecules vary from about ___ to
_______ amino acids in length.
• The types, sequences, and numbers of
amino acids used determine the type of
_________ produced.