Download II - Humble ISD

Name _________________________________________________________
Test Date ______________
UNIT 9 – PROTEIN SYNTHESIS
I. THE IMPORTANCE OF RNA (pp. 300-301)
The instructions in ________ are carried out through the making of _____________. Protein synthesis
occurs at the ___________________ in the ____________________ of the cell, but DNA is found in the
___________________. DNA cannot leave the nucleus because __________________________________,
so another molecule is required to take the genetic code from the nucleus to the _________________ so
protein synthesis can take place. This molecule is __________________________________ or ________.
A. RNA Structure – RNA differs from DNA in three ways:
Characteristic
Sugar
Base
Structure
DNA
RNA
RNA is able to leave the nucleus through the _________________________ because it is a
_________________________________; thus, the genetic code can be carried out.
B. Types of RNA – There are three principal forms of RNA involved in carrying out the genetic instructions
of DNA:
1. mRNA - _________________ RNA. Carries instructions (_________________) from DNA in
_______________ to __________________. “___________________” for genetic code.
2. tRNA - __________________ RNA. Carries (transfers) _________________________ to ribosome
according to instructions encoded in ____________.
3. rRNA - ________________ RNA. Structural component of ____________________; also produces
_____________________ to bond _________________________________ together to form
__________________.
II. PROTEIN SYNTHESIS
(pp. 301-306)
Protein synthesis takes place in two steps:
A. Transcription
The word “transcribe” means to ____________________. Transcription creates a _________________
copy of DNA’s instructions that can be carried out to the ___________________. Transcription takes
place in the ________________.
B. Translation
Translates or ____________________ the _____________________ sequence of ___RNA to an
___________________________ sequence to make a protein. Translation takes place at the
___________________.
III. A CLOSER LOOK AT TRANSCRIPTION, THE FIRST STEP IN PROTEIN SYNTHESIS
A. First, the enzyme ___________________________, unzips part of the DNA molecule.
B. RNA nucleotides are moved in according to base pairing rules and __________ is synthesized. There are
2 important ways that transcription differs from replication:
1. Only _____________________ of the DNA molecule is copied in transcription.
2. In RNA, the nucleotide that pairs with adenine is ________________. The nitrogen base,
____________________, is not found in RNA.
C. When the mRNA is first transcribed, there are long sequences of __________________ that are not
required for the synthesis of the protein called _______________. The DNA sequences that code for the
protein are known as ______________. Introns are edited out (cut out) of the mRNA before it leaves the
nucleus and the remaining __________ are spliced together to form the final mRNA.
D. mRNA leaves the ________________ through the ___________________________ and travels to the
______________________, the site of protein synthesis.
For the following “gene”, give the corresponding mRNA sequence:
TACCCGGAATTCGAG
___________________________________________________________________
IV. A CLOSER LOOK AT TRANSLATION, THE SECOND STEP IN PROTEIN SYNTHESIS
A. Codons – A Way to “Read” mRNA
The __________________ (building blocks) of proteins are ____________________. There are
______ amino acids used to build the proteins essential for life. The mRNA message is read by the
ribosome in groups of three _____________________ called _______________. Each codon codes
for a specific amino acid. A codon can be made up of any combination of the 4 nucleotides; in other
words, there are 4 X 4 X 4, or ______ possibilities for codons. Since there are only 20 amino acids,
many different codons represent the same amino acid. There are codons that are start (______) and
stop signals for the amino acid chain. The genetic code is _________________; that is, the same
__________ codes for the same _________________ in all organisms.
CODON CHART
For the following codons, give the name of the corresponding amino acid:
a. UAC - ___________________________________
b. GCA - __________________________________
c. AGA - __________________________________
d. CCU - __________________________________
For the following amino acids, give all the possible codons:
a. arginine - _____________________________________________________________________
b. glycine - ______________________________________________________________________
B. tRNA
The function of tRNA is to transfer the _____________________ specified by the __________________
to the ____________________ for protein synthesis. The _______________ of the cell is stocked with
all 20 amino acids required for protein synthesis. The tRNA molecule carries an ________________ at
one end and at the other end, it has a group of _____ nucleotides known as an ________________. The
anticodon binds to the mRNA codon cording to base pairing rules and insures that the proper amino acid
is brought to the ribosome.
C. Building a Protein
The ___________ slides through the ribosome a ____________ at a time. As the codon is read, the
tRNA with the corresponding _______________________ comes to the ribosome carrying its amino
acid. The next mRNA codon is read, and another __________ arrives with its amino acid, according to
its anticodon and base-pairing rules. As another tRNA arrives at the ribosome, the first tRNA is
bumped off, but it leaves its amino acid behind. This process continues and a chain of amino acids
forms until a stop codon is reached. Then the ribosome releases the amino acid chain, which coils &
folds to form a _______________.
V. GENETIC MUTATIONS
(pp. 307-308)
A mutation is a ________________________________________________________________
Although many mutations are harmful, some mutations are ______________, and others may be very
_____________________ to an organism. There are two categories of mutations:
A. Chromosomal Mutations
A chromosomal mutation involves a change in the _______________ of the entire chromosome or a
change in the total _____________ of chromosomes. Does not alter individual _____________. These
errors generally occur during __________________ or __________________.
B. Types of Chromosomal Mutations
C. Gene Mutations
A gene mutation is a change in one gene on an individual chromosome. This may result in a change in
only one ___________________ or many nucleotides making up that gene might be altered. The
incidence of gene mutations is relatively low due to the action of ___________________ that
________________________ the DNA sequence after ______________________________.There are
two types of gene mutations:
1. Point Mutations – This is a change in one or just a few ________________, but the total number of
nucleotides in the gene is not changed. This might have no effect, or change one amino acid.
Therefore, the resulting ________________ may or may not be altered.
2. Frameshift Mutations – This involves the _________________ or _________________ of a
_______________________. When a nucleotide is inserted or deleted, this shifts the reading of the
remainder of the _____________; therefore, the ___________________ of the remainder of the
mRNA is altered. This will usually result in tremendous changes in the ________________________
chain and completed protein.
Suggested Study Questions
p. 315 (3-10, 12-16, 18-21, 23)