genetics ch 15.

Which areas of an mRNA molecule do not encode a polypeptide? 3' UTR 5' UTR Coding region

3' UTR 5' UTR

Which nucleotide in a tRNA anticodon would bind to the U nucleotide in an mRNA codon? U T C A G

A

At the beginning of each round of elongation during translation, binding of the tRNA carrying the next amino acid to be added to the polypeptide binds occurs at the P site on the ribosome. (The P site holds the tRNA carrying the growing peptide chain.) Shine-Dalgarno sequence. A site on the ribosome. E site on the ribosome.

A site on the ribosome.

Which enzyme catalyzes the attachment of a specific amino acid to the correct tRNA? Peptidyl transferase Aminoacyl-tRNA synthetase Transfer RNA nucleotidyltransferase Amino acid transferase RNA polymerase

Aminoacyl-tRNA synthetase

To bring a specific amino acid into its location on a polypeptide chain, which sequence on transfer RNA must bind to messenger RNA? 3' sequence 5' sequence Anticodon Codon

Anticodon

Which of the following were used in the efforts to decipher the genetic code? Cell-free translation experiments using synthetic messenger RNAs Cell-free translation experiments using RNA copolymers with repeating patterns of nucleotides In vitro transcription assays to show which types of mRNA are produced Triplet-binding assays to determine which transfer RNAs bind to specific codons In vitro assays of specific tRNA and mRNA binding interactions

Cell-free translation experiments using synthetic messenger RNAs Cell-free translation experiments using RNA copolymers with repeating patterns of nucleotides Triplet-binding assays to determine which transfer RNAs bind to specific codons

Which one is NOT found in all transfer RNA molecules? One or more variable sites (Although structurally similar, tRNAs vary from each other at a few locations.) Amino acid acceptor stem with a 3' single-stranded region(A specific amino acid will be attached to the amino acid acceptor stem of each tRNA molecule.) Codon to specify which amino acid will be attached Stem-loop structures, with stabilized by hydrogen bonding on the stems Anticodon(The anticodon is located in the second loop region of an anticodon.)

Codon to specify which amino acid will be attached

Select all types of new information that led to modification of the original one-gene/one-enzyme hypothesis. Enzymes are not the only protein products of genes. One gene can be used to make more than one polypeptide. Some genes code for functional RNA products. Many genes can affect the same phenotypic trait. One gene can affect more than one phenotypic trait. Some proteins are made of more than one type of polypeptide.

Enzymes are not the only protein products of genes. One gene can be used to make more than one polypeptide. Some genes code for functional RNA products. Some proteins are made of more than one type of polypeptide.

True or false: The entire mRNA molecule encodes a polypeptide. True (There are regions on the mRNA that precede the start codon and follow the stop codon, they are called the 5' UTR and 3' UTR respectively.) False (There are regions on the mRNA that precede the start codon and follow the stop codon, they are called the 5' UTR and 3' UTR respectively.)

False

Which type of R group is consistent with an amino acid that is found on the exterior of a folded protein? Hydrophilic Neither hydrophilic nor hydrophobic Hydrophobic (Nonpolar, hydrophobic, amino acids are more likely to be buried within the interior of a protein.) Both hydrophilic and hydrophobic

Hydrophilic

Which type of R group is consistent with an amino acid that is found in the interior of a folded protein? Hydrophobic Neither hydrophobic nor hydrophilic Both hydrophobic and hydrophilic Hydrophilic (Polar, hydrophilic, amino acids are more likely to be on the surface of a protein.)

Hydrophobic

In the first step of initiation complex formation, which factors bind to the small ribosomal subunit to prevent it from associating with the large ribosomal subunit? tRNAfMet IF3 IF2 IF1 Peptidyl-transferase

IF3 IF1

Which description matches each stage of translation? Initiation Elongation Termination The newly produced polypeptide is released from the ribosome. Amino acids are linked together in the order designated by the codons. A complex form between the ribosomal subunits, one mRNA molecule and the first tRNA molecule.

Initiation -> A complex forms between the ribosomal subunits, one mRNA molecule and the first tRNA molecule. Elongation-> Amino acids are linked together in the order designated by the codons. Termination -> The newly produced polypeptide is released from the ribosome.

During bacterial translation, which component is found in a space between the 30S and 50S ribosomal subunits? Messenger RNA The polypeptide as it is synthesized Ribosomal proteins (Ribosomal proteins are a component of the ribosome.) Transfer RNA (Transfer RNA brings amino acids to the ribosome/mRNA complex.)

Messenger RNA

In prokaryotic cells, formation of the initiation complex requires the binding of tRNAfMet to the ____ site of the ribosome.

P

To form the initiation complex in prokaryotic cells, the transfer RNA carrying N-formylmethionine (tRNAfMet) binds to the E site. P site. A site. (It is believed that IF1 occupies part of the A site preventing tRNAfMet from binding to the A site.)

P site.

A polyribosome is a messenger RNA transcript that has many bound ribosomes in the act of translation. a messenger RNA bound to a ribosome with three or more subunits. a ribosome with three or more subunits. many ribosomes bound to transfer RNAs. (During translation, one ribosome can bind to two tRNAs at a time. Transfer RNAs are small molecules that cannot bind to more than one ribosome.) many messenger RNAs bound to the same two ribosomal subunits.

a messenger RNA transcript that has many bound ribosomes in the act of translation.

Cells of human muscle and adipose tissue have a protein receptor for insulin embedded in their plasma membranes. The receptor is a product of the INSR gene, where the dominant allele leads to a functional version of the protein. When insulin binds to this receptor, a cascade of reactions occurs that leads to an increase in the number of glucose transporters present in the membranes. This allows the uptake of glucose from the bloodstream into muscle and adipose cells. Some cases of insulin-resistance, observed in patients with obesity, are related to slower rates of glucose uptake. Which is the best explanation for differences at the cellular level for insulin-resistance contrasted with proper insulin response? People with insulin-resistance produce the insulin receptor while people with proper insulin response are lacking the receptor. People with insulin-resistance produce a lower level of the insulin receptors than people with proper insulin response. People with normal insulin response have an extra copy of the INSR gene that codes for the insulin receptor. People with insulin-resistance produce a higher level of insulin receptors than people with proper insulin response. People with insulin-resistance are missing the INSR gene that codes for the insulin receptor. (Loss of the receptor gene would be a lethal mutation.)

People with insulin-resistance produce a lower level of the insulin receptors than people with proper insulin response.

*Figure 15.4 The directionality of polypeptide synthesis* What is the name for the type of bond that joins the amino acids shown by the arrows in the diagram? Ionic bond Hydrogen bond Phosphodiester bond Peptide bond

Peptide bond

What is the role of initiation factors IF1 and IF3? Promote the formation of the peptide bond Promote messenger RNA binding to the ribosome Promote the binding of the first transfer RNA to messenger RNA )IF2, bound to GTP, promotes the binding of the first tRNA to the start codon on the mRNA.) Prevent messenger RNA from binding to the small ribosomal subunit (This action would inhibit translation.) Prevent the small ribosomal subunit from associating with the large ribosomal subunit

Prevent the small ribosomal subunit from associating with the large ribosomal subunit

The sequence of amino acids that results from gene transcription and mRNA translation represents which structure of the protein? Secondary structure Primary structure Quaternary structure Tertiary structure

Primary structure

Each of the 20 amino acids has a unique. carboxylic acid group. central carbon. amino group. R group.

R group.

The unique chemical properties of each amino acid are determined by its R group. carboxylic acid group. central carbon. amino group.

R group.

Which components are assembled into the subunits of a ribosome? Ribosomal RNA Transfer RNA Ribosomal proteins Messenger RNA

Ribosomal RNA Ribosomal proteins

Which type of codon would lead to the placement of a specific amino acid such as leucine into the polypeptide sequence? Sense codon Nonsense codon Start codon Stop codon

Sense codon

Select ways in which the one-gene/one-enzyme hypothesis had to be modified from its original form. Some genes encode functional RNA molecules rather than polypeptides. Alternative splicing and RNA editing can produce more than one polypeptide from a single gene. All proteins, including enzymes as well as other types of proteins, are encoded by genes. One gene encodes one polypeptide, which may be part of a protein made of multiple polypeptides. All proteins, including enzymes as well as other types of proteins, are encoded by genes. One gene encodes one protein, which may be made up of many different polypeptide chains. (this was the original hypothesis)

Some genes encode functional RNA molecules rather than polypeptides. Alternative splicing and RNA editing can produce more than one polypeptide from a single gene. All proteins, including enzymes as well as other types of proteins, are encoded by genes. One gene encodes one polypeptide, which may be part of a protein made of multiple polypeptides.

What term is used to identify multiple codons that encode the same amino acid (i.e. UUU and UUC both encode phenylalanine)? Missense codons Synonymous codons Nonsense codons Redundant codons Sense codons (Any codon specifying an amino acid is considered to be a sense codon.)

Synonymous codons

What dictates the pattern of folding of a protein? The chemical features of the R groups in the primary sequence The number of polypeptide chains that associate with each other (The folding pattern is determined by the primary sequence of the polypeptide.) The number of ionic bonds occurring in the secondary structure

The chemical features of the R groups in the primary sequence

Suppose you are comparing two cellular proteins that have different three-dimensional shapes. What is the determining factor that led to those differences? The two proteins have the same R groups, but different N groups. (All amino acids have the same N group.) The two proteins were synthesized at different speeds. The two proteins have different amino acid sequences. The two proteins were produced by different ribosomes.

The two proteins have different amino acid sequences.

According to the wobble rules, which base of the codon can be mismatched with an anticodon base on the tRNA? None of the three bases of the codon Third base of the codon Any of the three bases of the codon First base of the codon Second base of the codon

Third base of the codon

Which of the following represent common structural features of transfer RNA molecules? Codon sequence to specify which amino acid will bind Three stem-loops Amino acid acceptor stem with a 3' single-stranded region Anticodon sequence A small number of variable sites

Three stem-loops Amino acid acceptor stem with a 3' single-stranded region Anticodon sequence A small number of variable sites

*Figure 15.10 Secondary structure of tRNA* Which type of RNA is shown in the figure? Ribosomal RNA Messenger RNA Transfer RNA

Transfer RNA

During which process is the code of mRNA used to synthesize a polypeptide? Transcription Replication Translation

Translation

Which method uses a three-nucleotide RNA molecule to cause a ribosome to bind the tRNA carrying that amino acid? Codon-binding assay Triplet-binding assay Cell-free translation of synthetic mRNA mixtures Amino acid-binding assay Cell-free translation of copolymers

Triplet-binding assay

Which nucleotide in a tRNA anticodon would bind to the A nucleotide in an mRNA codon? G C T U A

U

For translation in vertebrates and vascular plants, the AUG used as the start codon requires specific bases in the surrounding sequences, including a pyrimidine at position -3, preferably a cytosine. a purine at position -3, preferably adenine, but guanine will also work. an adenine at position +4. a guanine at position +4. a cytosine at position +1..

a purine at position -3, preferably adenine, but guanine will also work. a guanine at position +4.

For bacterial translation, the mRNA is found within a space between the ribosomal subunits, and the polypeptide exits through a channel within the large ribosomal subunit. a channel in the small ribosomal subunit, and the polypeptide exits through a channel in the large ribosomal subunit. (The mRNA is found in a space between the two subunits.) a channel in the large ribosomal subunit, and the polypeptide is located within a space between the ribosomal subunits.

a space between the ribosomal subunits, and the polypeptide exits through a channel within the large ribosomal subunit.

An aminoacyl-tRNA is a transfer RNA that is ready to pick up an amino acid. a transfer RNA that has delivered its amino acid to a growing peptide chain. a transfer RNA with an amino acid attached to its 3' end. a transfer RNA with an amino acid attached to its 5' end.

a transfer RNA with an amino acid attached to its 3' end.

The location on a transfer RNA where an amino acid becomes attached is the variable site. stem-loop structure. anticodon. (The anticodon is the site that is complementary to the mRNA codon.) acceptor stem with a 3' single-stranded region. 5' end with a double-stranded region.

acceptor stem with a 3' single-stranded region.

Francis Crick proposed that certain types of RNA molecules were involved in the incorporation of amino acids into a polypeptide chain in the ____ hypothesis.

adaptor

To account for the involvement of RNA molecules for incorporating amino acids into a protein chain, Francis Crick proposed the base-pairing hypothesis. genetic code hypothesis. wobble hypothesis. (Crick proposed the wobble hypothesis to account for the redundancy of the genetic code.) adaptor hypothesis.

adaptor hypothesis.

The single-stranded region at the 3' end of a transfer RNA is the location where a(n) ______ becomes attached. 7-methyl guanosine cap poly-A tail hydroxyl group carboxyl group amino acid

amino acid

The location on a polypeptide where a nitrogen (N) atom can be found is the ____-____

amino terminus

When a polypeptide is synthesized, the first amino acid to be put in place is located at the __-___

amino-terminus

The first amino acid in a polypeptide chain is located at the carboxyl-terminus. R-terminus. amino-terminus. central-terminus.

amino-terminus.

A transfer RNA that has an amino acid attached to its 3' end is called a(n) ____-tRNA.

aminoacyl

To explain why patients had a buildup of the urine-darkening metabolite homogentisic acid, Archibald Garrod proposed that they were lacking an enzyme that would metabolize homogentisic acid. mitochondria. ribosomes to make metabolic enzymes. receptors for homogentisic acid.

an enzyme that would metabolize homogentisic acid.

A series of three nucleotides in transfer RNA that is complementary to a codon in messenger RNA is called a(n) ___

anticodon

The function of an aminoacyl-tRNA synthetase enzyme is to catalyze the synthesis of tRNA. attachment of an amino acid to its appropriate tRNA. binding of a tRNA anticodon to a mRNA codon. addition of a single-stranded sequence to the 3' end of the tRNA. addition of amino acids to a growing polypeptide chain.

attachment of an amino acid to its appropriate tRNA

In addition to cell-free translation experiments with mixtures of synthetic RNAs, efforts to decipher the genetic code included transcription assays and cell-free translation of copolymers. DNA-RNA binding assays and triplet-binding assays. (Deciphering the genetic code involves a study of translation, which does not directly involve DNA.) in vivo assays of specific amino acid and mRNA binding interactions cell-free translation of copolymers and triplet-binding assays.

cell-free translation of copolymers and triplet-binding assays.

To decipher the genetic code, scientists were able to synthesize radioactively-labeled polypeptides from synthetic messenger RNAs in a cell-free translation system. tRNA-free translation system. cell-free transcription system. ribosome-free translation system.

cell-free translation system.

A protein that assists with the proper folding of other polypeptides is a(n) ____

chaperone

Proper folding of some polypeptides requires the assistance of a(n) transfer RNA. enzyme. (Folding is based on the primary structure of the peptide chain and is facilitated by a type of protein that binds to the polypeptide.) chaperone. ribosome.

chaperone.

Both eukaryotic and prokaryotic cells have ribosomes in the ____

cytosol

A plant cell will have ribosomes in its chloroplasts only. cytosol only. mitochondria only. cytosol and chloroplasts only. (Plant and algal cells are eukaryotic and they have ribosomes in their chloroplasts and mitochondria.) cytosol, mitochondria and chloroplasts.

cytosol, mitochondria and chloroplasts.

Amino acids are added sequentially to a growing polypeptide chain during initiation. elongation. termination.

elongation.

Archibald Garrod proposed that the buildup of homogentisic acid leading to the symptoms of alkaptonuria resulted from a missing _____

enzyme

The bacterial RNA polymerase core enzyme is composed of five different polypeptide chains. The number of genes needed to code for this enzyme is ______. Assume alternative splicing is not used here.

five

A sequence of bases that begins with the start codon and continues to the end of the coding sequence by reading the bases in groups of three is called the _____ ____

genetic code

Arranging the four RNA nucleotides A, G, C and U in groups of three with all possible combinations leads to a set of codons called the gene sequence. ribosomal RNA sequence. genetic code. transfer RNA sequence. amino acid sequence. (The genetic code is comprised of codons, located within a molecule of mRNA.)

genetic code.

Translation is divided into three stages: the first is ___, the next is ___, and the last is ____ .

initiation, elongation and termination

The Shine-Dalgarno sequence facilitates the binding of the first tRNA to the P site of the ribosome. (The sequence facilitates mRNA binding to the ribosome.) mRNA to the small ribosomal subunit. mRNA to the large ribosomal subunit. (mRNA binds to the small ribosomal subunit.) the second tRNA to the A site of the ribosome.

mRNA to the small ribosomal subunit.

The bond formed between the carboxylic acid group of one amino acid and the amino group of the next amino acid is a(n) ______ bond. ionic phosphodiester hydrogen peptide

peptide

The combination of a messenger RNA and many bound ribosomes in the process of translation is called a(n) ____

polyribosome

The consecutive order of amino acids in a polypeptide chain represents its____structure.

primary

In ______ cells, the initiator tRNA is carrying the amino acid N-formylmethionine. prokaryotic eukaryotic

prokaryotic

Genes that determine the amino acid sequence of a polypeptide are called ___-___ genes, or structural genes.

protein encoding

Genes that determine the order of amino acids found in a polypeptide are called ribosomal RNA genes. transfer RNA genes. protein-encoding genes.

protein-encoding genes.

Each ribosomal subunit is assembled from ribosomal RNA and many different ____

proteins

Properties such as cell shape and organization and cellular movement depend upon the direct action of which type of cellular component? Carbohydrates Lipids Proteins Nucleic Acids

proteins

For a protein, an association of two or more polypeptide chains represents its ____ structure.

quaternary

The oxygen-carrying molecule hemoglobin is an association of four polypeptides, two called α-hemoglobin and two called β-hemoglobin. The level of protein structure demonstrated by hemoglobin is secondary structure. tertiary structure. quaternary structure. primary structure.

quaternary structure.

Beginning with the start codon and reading the following bases in groups of three determines the reading frame. transcript. genomic DNA sequence. untranslated region.

reading frame.

The complex of rRNA and protein that acts as the site of translation is the _____

ribosome

Translation takes place on a structure called the ____

ribosome

*Figure 15.6 Levels of structures formed in proteins* For polypeptides, alpha (α) helix and beta (β) sheet represent ____ structures.

secondary

The initial folding of a polypeptide into a regular repeating shape represents its ____structure.

secondary

The protein structure stabilized by the formation of hydrogen bonds between atoms found in the polypeptide backbone is primary structure. quaternary structure. secondary structure. tertiary structure.

secondary structure.

Which are the twenty-first and twenty-second amino acids that can be used in protein synthesis? phosphocysteine and acetyl-lysine selenocysteine and pyrrolysine acetylserine and acetylthreonine hydroxyproline and homoserine

selenocysteine and pyrrolysine

An exception to the genetic code involves the incorporation of which of the following chemically modified amino acids into polypeptides? selenocysteine. methyl-lysine. pyrrolysine. methyl-arginine acetylcysteine.

selenocysteine. pyrrolysine.

A series of three nucleotide bases that specifies the insertion of a particular amino acid into a polypeptide chain is a ___ ___

sense codon

A set of three-letter combinations of nucleotides called codons, each of which corresponds to a specific amino acid, represents the ____ _____

sense codon

A 9-nucleotide sequence in prokaryotic mRNA that facilitates binding to the small ribosomal subunit is the ___- ___sequence.

shine-dalgarno

In experiments where Beadle and Tatum were able to deduce the steps in a biochemical pathway, they concluded that a single gene controlled the synthesis of a ______ ______. single carbohydrate single enzyme Second single chromosome single gene (The statement refers to the control of the synthesis of a component required in a biochemical pathway.)

single enzyme

In experiments where Beadle and Tatum were able to deduce the steps in a biochemical pathway, they concluded that the synthesis of a single enzyme was controlled by a ______ single enzyme (At the DNA level, one gene will control the synthesis of one enzyme.) Second single chromosome single gene

single gene

An AUG codon, which specifies the amino acid methionine and is often the first codon that begins a polypeptide sequence, is called a ____ codon.

start

In prokaryotic cells, a transfer RNA carrying N-formylmethionine recognizes the ______ and is the first tRNA to bind to the ribosomal subunits, so it is called the initiator tRNA. start codon exon operon stop codon promoter

start codon

A series of three nucleotide bases that specifies the placement of the amino acid methionine at the beginning of a polypeptide chain is a synonymous codon. start codon. stop codon. nonsense codon.

start codon.

The signal for termination of translation is called a(n) ____ codon.

stop

A series of three nucleotide bases that signals the end of a polypeptide chain is a(n) sense codon. start codon. antisense codon. synonymous codon. stop codon.

stop codon.

For translation in vertebrates and vascular plants, the AUG chosen as the start codon will be the AUG closest to the Shine-Dalgarno sequence. the AUG closest to the 5' end of the mRNA. the AUG closest to the 3' end of the mRNA. (In many, but not all, cases, the ribosome uses the first AUG it encounters near the 5' end. The sequence of bases around the AUG codon plays an important role in determining whether or not it is selected as the start codon.) surrounded by specific bases as defined by Kozak's rules.

surrounded by specific bases as defined by Kozak's rules.

The codons UUU and UUC both encode phenylalanine, thus they are called ____ ____

synonymous codon

To decipher the genetic code, a cell-free translation system containing ribosomes, tRNAs, enzymes and radioactive amino acids was used to synthesize prokaryotic DNA from RNA. synthesize messenger RNAs from prokaryotic DNA. (The system tests the products of translation rather than transcription.) synthesize radioactively-labeled polypeptides from synthetic messenger RNAs. synthesize radioactively-labeled polypeptides in the absence of mRNA. (RNA always is required for translation, whether it is naturally produced as mRNA or synthetically made.) directly observe codon-anticodon binding.

synthesize radioactively-labeled polypeptides from synthetic messenger RNAs.

The folded-three dimensional conformation of a polypeptide represents its ____ structure.

tertiary

The folding of α helical regions and beta-sheet regions relative to each other leads to formation of a polypeptide's primary structure. quaternary structure. secondary structure. (The secondary structure consists of alpha helices and beta pleated sheets. When these are further folded it produces the proteins tertiary structure.) tertiary structure.

tertiary structure.

Cells of the pancreas secrete the hormone insulin to assist with glucose uptake while neurons release neurotransmitters to conduct nerve signals. The difference in products released by these two types of cells depends on differences in the genetic code between the two types of cells. (The genetic code is identical for different cell types in the same organism.) differences in the structure of ribosomes found in each type of cell. DNA content between the two types of cells. (The DNA content of these two types of cells is identical.) the types of proteins produced within each cell.

the types of proteins produced within each cell.

The synthesis of a protein using the sequence of codons in a messenger RNA is called ____

translation

Researchers could determine the codon that specified a particular amino acid in an experiment where a three-nucleotide RNA molecule caused a ribosome to bind the tRNA carrying that amino acid. This experimental method is called the ____-___ assay.

triplet-binding

Codons UUC and UUU lead to the placement of phenylalanine at a specific position in the protein chain. This type of mismatch in codon-anticodon binding that can occur at the third base of the codon is called ____

wobble

*Figure 15.6 Levels of structures formed in proteins* Which of the following represent secondary structures observed in polypeptides, as shown in the diagram? β (beta) sheet double helix condensed globular structure hairpin loop α (alpha) helix

β (beta) sheet α (alpha) helix