gene expression 2 Flashcards
Polypeptides are made from mRNA during
translation
The genetic code specifies the relationship between the sequence of nucleotides in ______ and the sequence of amino acids in a polypeptide.
mRNA
There are __ nucleotide bases in one codon.
3
How many amino acids can be specified by a codon?
1
Which of the following statements best describes the genetic code?
- It is universal; no exceptions have been discovered
- It is not universal; a lot of exceptions have been discovered
- It is nearly universal; only a few rare exceptions have been discovered
It is nearly universal; only a few rare exceptions have been discovered
The synthesis of __ using information within the mRNA is called translation.
polypeptides, proteins, polypeptide, or protein
Because the same amino acid can be specified by more than one codon, the genetic code is characterized as ______.
degenerate
What is the purpose of the genetic code?
It specifies the relationship between mRNA and polypeptide sequences.
Codons that specify the same amino acid typically differ in the base at position number __.
3
The genetic code is read in groups of three nucleotide bases known as __.
codons
The start codon encodes the amino acid
methionine or met
A codon in a messenger RNA molecule consists of ______ nucleotides. Each mRNA codon specifies ______ amino acid(s).
three; one
The portion of an mRNA sequence that specifies the amino acid sequence of a polypeptide is called the __ sequence.
coding
The genetic code is said to be nearly __ because with few exceptions, all organisms use the same code.
universal or identical
The end of translation is signaled by the
stop codon
The genetic code is said to be __ because more than one codon can specify the same amino acid.
degenerate or redundant
In most cases, codons that specify the same amino acid vary in the ________ base.
third
What part of a tRNA binds to the codon of a messenger RNA molecule?
Anticodon
What amino acid is specified by the start codon?
Methionine
There are __ nucleotides are in an anticodon.
3
A coding sequence specifies the amino acid sequence of a(n)
polypeptide or protein
Which part of a tRNA molecule binds to a codon on mRNA to determine which amino acid will be added to a growing polypeptide?
Anticodon
A stop codon specifies the end of
translation.
Which RNA molecule functions as an intermediary between an mRNA codon and an amino acid?
The tRNA
Because the same amino acid can be specified by more than one codon, the genetic code is characterized as ______.
degenerate
The components mRNA, tRNA, ribosomes, and translation factors must be made by a cell so that __ can be synthesized.
polypeptides, proteins, or protein
What is the function of the anticodon of a tRNA molecule?
It binds to a codon on an mRNA molecule.
The three major types of RNA are involved in translation. The information to synthesize a polypeptide sequence is contained in __; Amino acids are brought to the ribosome by __; and __ is a major component of the ribosome.
Blank 1: mRNA or messengerRNA
Blank 2: tRNA or transferRNA
Blank 3: rRNA or ribosomalRNA
In a tRNA molecule, the anticodon is a ______-base sequence.
three
The structural features common to all transfer RNAs include a stem-loop containing a(n) __ that is complementary to the codon on mRNA and an acceptor stem where a(n) __ __ can be attached.
Blank 1: anticodon or anti-codon
Blank 2: amino
Blank 3: acid
The __ in tRNA binds to a codon in an mRNA.
anticodon
A __-__ structure in a tRNA molecule consists of a region where the RNA is double-stranded due to complementary base pairing, and another region without base pairing.
stem-loop or hair-pin
The __ molecule is attached to an amino acid and has an anticodon that can base pair with a codon.
tRNA or transferRNA
Which of the following components are necessary for translation?
- translation factors
- RNA polymerase
- ribosomes
- tRNA
- spliceosomes
- mRNA
translation factors
ribosomes
tRNA
mRNA
mRNA function
contains information needed to synthesize a polypeptide
tRNA function
binds to a codon and carries the appropriate amino acid to be added to the polypeptide
ribosome function
catalyzes the formation of peptide bonds to synthesize a polypeptide
translation factor function
proteins required for translation
What structural features are common to all tRNAs?
- Acceptor stem for amino acid attachment
- A, P, and E sites
- Cloverleaf pattern with three stem-loops
- Loop that attaches to the spliceosome
Acceptor stem for amino acid attachment
Cloverleaf pattern with three stem-loops
What must be attached to the 3’ end of a tRNA molecule in order for translation to proceed properly?
An amino acid
A tRNA molecule assumes a stem-loop structure which results from ________ bonds that form between nearby regions.
hydrogen
What is attached to a charged tRNA molecule?
An amino acid
The components mRNA, tRNA, ribosomes, and translation factors must be made by a cell so that __ can be synthesized.
polypeptides, proteins, or protein
The three major types of RNA are involved in translation. The information to synthesize a polypeptide sequence is contained in __; Amino acids are brought to the ribosome by __; and __ is a major component of the ribosome.
Blank 1: mRNA or messengerRNA
Blank 2: tRNA or transferRNA
Blank 3: rRNA or ribosomalRNA
What is the site of translation?
Ribosome
In order for translation to be accurate, the appropriate amino acid must be attached to the:
3’ end of the correct tRNA
What are the two subunits of a ribosome called?
Large and small subunits
A __-__ structure in a tRNA molecule consists of a region where the RNA is double-stranded due to complementary base pairing, and another region without base pairing.
stem loop or hairpin
The ribosomal subunits contain two types of macromolecules:
Blank 1: protein, proteins, or polypeptides
Blank 2: rRNA, RNA, RNA molecules, ribonucleic acid, ribosomalRNA, RNAs, nucleic acids, nucleic acid, ribonucleicacid, or RNAmolecules
A tRNA molecule with its attached amino acid is called a(n) __ tRNA.
charged, aminoacyl, or aminoacylated
Which of the following components are necessary for translation?
- translation factors
- RNA polymerase
- tRNA
- spliceosomes
- mRNA
- ribosomes
translation factors
tRNA
mRNA
ribosomes
What are the names of the three sites where tRNA molecules bind to the ribosome?
- the exit site
- the peptidyl site
- the anticodon site
- the aminoacyl site
- the codon site
the exit site
the peptidyl site
the aminoacyl site
Translation occurs on structures called
ribosomes
Translation occurs in three stages: initiation, __, and __.
elongation
termination
A(n) __ is composed of structures called the large and small subunits.
ribosome
Which macromolecules are found in ribosomes?
- polysaccharides
- DNA
- RNA
- protein
- phospholipids
RNA
protein
During the initiation stage of translation, an mRNA molecule, the first (initiator) __ molecule, and the ribosomal subunits associate. During elongation, __ bonds are formed between amino acids. Finally, translation ends when the ribosome reaches a(n) __ codon.
Blank 1: tRNA or transferRNA
Blank 2: peptide or covalent
Blank 3: stop, termination, nonsense, or non-sense
A ribosome contains three discrete sites where tRNAs may be located. These are known as the A or __ site, the P or __ site, and the E or __ site.
Blank 1: aminoacyl
Blank 2: peptidyl
Blank 3: exit
What molecules must assemble during the initiation stage of translation?
- ribosomal subunits
- the first tRNA
- mRNA molecule
- the DNA molecule
ribosomal subunits
the first tRNA
mRNA molecule
The stages of translation are called:
initiation, elongation and termination
In most cases, the start codon used for translation is
AUG or ATG
What are the two subunits of a ribosome called?
Large and small subunits
During initiation of translation, the initiator tRNA recognizes the __ codon in mRNA and binds to it.
start, AUG, starting, initiation, methionine, or starter
The ribosomal subunits contain two types of macromolecules:
Blank 1: protein, proteins, or polypeptides
Blank 2: rRNA, RNA, RNA molecules, ribonucleic acid, ribosomalRNA, RNAs, nucleic acids, nucleic acid, ribonucleicacid, or RNAmolecules
key events that occur during Initiation
The mRNA, tRNA, and ribosomal subunits are assembled.
key events that occur during Elongation
Peptide bonds are formed between amino acids to synthesize a polypeptide.
key events that occur during termination
A release factor binds to the A site of the ribosome.
During the initiation phase of translation, a complex is formed between an mRNA molecule, the first __, and the __ subunits.
Blank 1: tRNA, transferRNA, transfer RNA, or tRNA molecule
Blank 2: ribosomal or ribosome
In a strand of mRNA, the nucleotide sequence of the start codon is
AUG.
Which tRNA recognizes and binds to the start codon in mRNA?
Initiator tRNA
In bacteria, translation is initiated when a(n) __ molecule binds to the small ribosomal subunit.
mRNA, messengerRNA, or RNA
Which macromolecules are found in ribosomes?
- phospholipids
- DNA
- polysaccharides
- protein
- RNA
protein
RNA
The __ stage of translation involves the covalent bonding of amino acids to each other, one at a time.
elongation or second
During the initiation stage of translation, an mRNA molecule, the first (initiator) __ molecule, and the ribosomal subunits associate. During elongation, __ bonds are formed between amino acids. Finally, translation ends when the ribosome reaches a(n) __ codon.
Blank 1: tRNA or transferRNA
Blank 2: peptide or covalent
Blank 3: stop, termination, nonsense, or non-sense
What is attached to a peptidyl tRNA?
A short polypeptide
What molecules must assemble during the initiation stage of translation?
the first tRNA
mRNA molecule
ribosomal subunits
Because the anticodon in the tRNA is complementary to the codon in the mRNA, during the elongation phase of translation, a charged tRNA carrying a single amino acid binds to the ______ site.
A
In most cases, the start codon used for translation is
AUG or ATG
To obtain the energy required for tRNA to bind to the A site, elongation factors hydrolyze:
GTP
Identify the stage of translation in which polypeptide synthesis occurs.
Elongation
The peptidyl transfer reaction involves the removal of the polypeptide from the tRNA in the ______ site and its transfer to the amino acid in the ______ site.
P ; A
A tRNA with a polypeptide attached to it is called a(n):
peptidyl tRNA
A charged tRNA molecule carrying a single amino acid binds to the A site because the anticodon in the tRNA has a sequence that is __ to the codon in the mRNA.
complementary or corresponding
Proteins functioning as elongation factors provide the energy for binding tRNA to the ______ site.
A
In bacteria, translation is initiated when a(n) __ molecule binds to the small ribosomal subunit.
mRNA, messengerRNA, or RNA
During the elongation stage of translation, the polypeptide is removed from the tRNA in the P site and added to the tRNA in the A site. This event is termed the ___ ____ reaction.
Blank 1: peptidyl
Blank 2: transfer or transferase
The peptidyl transferase center, which catalyzes the peptidyl transfer reaction, is composed of several proteins and
rRNA
What is attached to a peptidyl tRNA?
A short polypeptide
During the translocation step of protein synthesis, the ribosome moves toward the
3’ end of mRNA by exactly one codon
Because the anticodon in the tRNA is complementary to the codon in the mRNA, during the elongation phase of translation, a charged tRNA carrying a single amino acid binds to the ______ site.
A
To obtain the energy required for tRNA to bind to the A site, elongation factors hydrolyze:
GTP
In the process of protein synthesis, what recognizes the three stop codons?
A protein called release factor
The three-dimensional structure of a release factor protein mimics the structure of
tRNAs
The peptidyl transfer reaction that occurs in translation is catalyzed by
a region in the 50S subunit
What happens as a result of the translocation step of protein synthesis?
- The next codon moves into the P site
- The tRNA in the P site moves into E site
- The tRNA in the A site moves into P site
- The next codon moves into the A site
- The tRNA in the P site moves into A site
- The tRNA in the A site moves into E site
The tRNA in the P site moves into E site
The tRNA in the A site moves into P site
The next codon moves into the A site
A charged tRNA molecule carrying a single amino acid binds to the A site because the anticodon in the tRNA has a sequence that is __ to the codon in the mRNA.
complementary or corresponding
During translation, the stop codons are recognized by a protein called a(n) )__ factor.
release
The translation release factor has a 3-D structure that resembles that of:
tRNA
During bacterial translation, when a stop codon is encountered, a protein known as a(n) _ factor binds to the A site, which triggers the removal of the _ from the tRNA in the P site.
Blank 1: release
Blank 2: polypeptide or protein
During the translocation step of protein synthesis, the ribosome moves toward the
3’ end of mRNA by exactly one codon
Because the anticodon in the tRNA is complementary to the codon in the mRNA, during the elongation phase of translation, a charged tRNA carrying a single amino acid binds to the ______ site.
A
The three-dimensional structure of a release factor protein mimics the structure of
tRNA
