Biology 12-3 RNA and Protein Synthesis
Objectives for this section
 Compare and contrast DNA and RNA
 Name the 3 main types of RNA
 Describe transcription and the editing of RNA
 Identify the genetic code
 Summarize translation
 Explain the relationship between genes and proteins
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The _____________________ of DNA explains how it can be ______________, but it does not tell how a
_________ ________________.
____________—coded DNA instructions that control the production of proteins within the cell
We now know that the _____________ ______________ of biology is ________ to _______ to
__________________
o The first step in __________________ the genetic message is to _________ part of the
________ nucleotide ________________ into RNA (ribonucleic acid)
o These ________ molecules contain the ______________ instructions for making
_________________
The Structure of RNA
 _________, like _________, is a long chain of ___________________
 _________ consists of the same _____________________ as _________
o A ____________________________
o A ____________________________
o A ____________________________
 There are _______ main _____________________ between DNA and RNA
o The _____________ in RNA is _______________ instead of the _____________________ in
________
o __________ is generally _____________-___________________
o RNA contains ____________ instead of _________________
 RNA is like a ___________________ copy of a __________________ of DNA
 In many cases, ________ is a copy of a _______________ ______________—the ability to copy a single
DNA sequence into RNA makes it possible for a single gene to produce hundreds or even thousands of
RNA molecules
Types of RNA
 _______ molecules have many ________________, but in the majority of cells most RNA molecules are
involved in just one job—___________________ __________________
 There are 3 main types of RNA
o ______________________________ (_____________)—carry copies of instructions for
assembling amino acids into proteins; serve as “messengers” from DNA to the rest of the cell
o ______________________________ (___________)—a component of ribosomes
o ______________________________ (_____________)—works during the construction of a
protein; transfers each amino acid to the ribosome as it is specified by the coded messages in the
mRNA
Transcription
 ______________________________—when RNA molecules are produced by copying part of the
nucleotide sequence of DNA into a complementary sequence in RNA
 Transcription requires the ________________ ________ _____________________—binds to DNA and
separates the DNA strands. Then uses one strand of DNA as a template from which nucleotides are
assembled into a strand of RNA
 How does the RNA polymerase know where to start and stop making the RNA copy?
o The ______________ will only bind to _________________ of DNA known as
_____________________, which have specific ________ ___________________
o Similar _________________ tell the RNA _________________________ where to stop
RNA Editing
 The first molecule of _____________ (known as the ___________________) produced by copying the
DNA ________________________ is like a rough ______________ and it requires
_____________________
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DNA contains sequences of ____________________ called _____________, which are not involved in
__________________ for ___________________
The DNA _________________ that code for ___________________ are called ___________, because they
are expressed in the _________________ of ________________
When an ______ molecule is formed, it contains both _________________ and ____________
o The ________________ are cut out of the _______ molecule while it is still in the
_________________
o The remaining _____________ are _______________ back together and form the final
_______________________ molecule
The Genetic Code
 Remember that proteins are made by joining _____________ _________________ into long chains called
_________________________
o Each _____________________ contains a combination of any or all of the _____ different
__________________ ________________
o The __________________ of _________________ are determined by the order in which
different amino acids are joined together to produce __________________________
 The “___________________” of mRNA instructions is called the __________________ _____________
o ___________ contains 4 different _______________________ bases (____, ____, ____, ____)
o How can a code with only 4 letters translate into 20 different amino acids?
o The ____________________ code is read ______ letters at a time, so each “_____________” of
the coded message is 3 ______________ long
 Each 3-letter “_____________” in mRNA is known as a _____________________
 A _____________ consists of 3 consecutive _______________________ that specify a _______________
amino acid that is to be added to the ____________________________
 Example: UCGCACGGU would be read as _______-________-__________. These codons represent 3
amino acids: _________________-________________-_________________
 Because there are ______ different bases, there are _______ possible _____-base codons.
o Note that some ______________ ______________ can be _______________________ by more
than one ________________
o There are also “______________” and “________________” codons
 ______________ codons (__________) tell where protein synthesis is to
__________________
 ________________ condons (_____ different ones) tell where the _________ of the
___________________________ is
Translation
 The mRNA molecule has been _______________________ and serves as _____________________, but
we need something to read the instructions and put them to use
o In the cell, the _______________________ takes care of this
 ________________________—the decoding of an mRNA message into a polypeptide chain (protein)
 Steps in translation
o Begins when an __________________ molecule in the __________________ attaches to a
___________________
 Each ______________ of the mRNA moves through the _____________________ and
the proper amino acid is brought to the ___________________________ by the
_________
 Each ____________ carries only one kind of amino acid and picks it up based on the
______________________ it is carrying
 Example: if the __________________ is UUU, the tRNA would pick up the
amino acid with the codon ______________ (they are
_________________________)
o The ______________________ forms a peptide ______________ between the first and second
amino acids
 At the same time, it _________________ the bond with the _________ molecule and
releases it
 The ___________________ moves on to the third amino codon, where a __________
molecule brings it the amino acid ______________________ by the third
________________
o The ___________________________ chain continues to grow until the
__________________________ reaches a ___________ _________________ on the mRNA
molecule
 When the _____________ codon is reached, it releases the newly formed
_______________________ and ___________ molecule, completing the process of
_________________________
Genes and Proteins
 What does ___________________ ______________________ have to do with the color of a flower, eye
color, or height?
 Remember that many proteins are ________________, which ______________________ and
______________________ chemical reactions.
o A _____________ that codes for an ____________________ to produce pigment controls flower
color.
 ______________________ are _______________________ tools that build or operate
__________________________ of living cells.