Cell Bio Final TopHat/Homework Questions
Many transcriptional activators are composed of two or more independent _____, each with its own separate function
Domains
Why can't a digest of human genomic DNA be resolved by gel electrophoresis
A typical digest of the human genome produces too many fragments to resolve
The pH of endosmoses and lysosomes is
Acidic
Protein transport into the ER or mitochondria requires unfolding of the protein and threading the amino acid chain through a channel or pore into the organelle. In contrast, protein transport into the nucleus does not require unfolding of the protein. Why is unfolding necessary for nuclear protein import?
Because the protein is carried by an import in protein through the nuclear pore complex
If a human gene is found to have 5 introns, then the mature mRNA encoded by that gene would have how many exons?
Between 1 and 6
WHich of the following lipids are distinctly enriched in lipid rafts?
Cholesterol and sphingolipids
The characterization of restriction endonucleases was a key step in the development of recombinant DNA technology. What is the function of these enzymes?
Cleavage of double-stranded DNA at specific sequences
What are two likely reasons that the NLS is not cleaved off for nuclear proteins?
It is necessary for transporter proteins to bind
Which statement about heterochromatin is FALSE?
It is transcriptionally active
What statement is true about Myosin I
It links actin bundles to the plasma membrane in the microvilli of intestinal cells
What is NOT true of the assembly of actin filaments
It requires ATP
What are the expected phenotypic consequences of a mutation in RanGAP that reduces its affinity for cytoplasmic filaments of the nuclear pore?
It would include less transportation of molecules into the nucleus due to the lack of conversion of GTP to GDP on import in proteins
NADH produced in glycolysis yields fewer ATP molecules than that produced in the citric acid cycle because
Its electrons are shuttled across the mitochondrial inner membrane to complex II
The fibrous proteins underlying the inner mitochondrial membrane are
Lamins
Membrane proteins are able to move
Laterally within the plane of the membrane
Eukaryotic transcriptional activators have activation domains that interact with
Mediator proteins and transcription factors
Injection of MPF into frog oocytes induces them to enter
Meiosis
Transport of glucose into the intestinal epithelium is driven by ion gradients established by the
Na+-K+ pump
Which molecule has a critical role in transcription elongation
P-TEFb
The DNA sequence to which an RNA polymerase binds to initiate transcription of a gene is called a(n)
Promoter
An important step in the import of the transcription factor NF-KB into the nucleus is regulated by a
Protease
SH2 domains are
Protein domains that bind phosphotyrosine-containing peptides
Zellweger syndrome is caused by a defect in
Protein import into peroxisomes
Most of the effects of cAMP in the cell are mediated by
Protein kinase A
What is NOT one of the functions of the cytoskeleton?
Protein translocation into the ER
Tim and Tom are
Protein translocators in mitochondrial membranes
Which of the following is NOT involved in receptor mediated endocytosis
Pseudopodia
What is not involved in the tissue-specific expression of the immunoglobulin heavy-chain gene?
RNA polymerase II
What are the two families of small GTP-binding proteins that are involved in the formation of coated vesicles?
Rab and ARF proteins
LDL uptake by cells is one of the functions of
Receptor-mediated endocytosis
Monosaccharides are to ____ as _____ are to RNA.
Starch; Nucleotides
Lipids play important roles in a number of functions. What is not one of those functions?
Storage of genetic material
In dogs, the Fgf4 gene encodes a protein that regulates bone growth, and in its normal chromosomal location, Fgf4 yields dogs with long legs. WHich statement best explains the mechanism leading to a short-legged phenotype in dogs?
The Fgf4 gene is retrotransposed into the middle of a LINE that contains mutated regulatory sequences that give abnormal expression of Fgf4
What is true about ion channels?
They open either by the binding of ligands or by changes in electrical potential across the membrane
What is the function of karyopherins
They transport macromolecules into/out of the nucleus
Which of the following deletions will not change the reading frame of a gene?
Three nucleotides
Proteins are translated into the ER lumen
Through an aqueous channel created by the Sec61 protein
In the polymerase chain reaction, the purpose of the step in which the temperature is between 70 C and 75 C is
To allow DNA polymerase to synthesize DNA
The primary function of rRNAs in the ribosome is
To catalyze peptide bond formation
The function of telomeres is
To ensure chromosome replication and maintenance
Many cancers arise as a result of a breakdown in signaling pathways that control cell proliferation (T/F)
True
A centrosome is
the major microtubule-organizing center in animal cells
The 5' end of mRNA is modified by
Capping with 7-methylguanosine
The unfolded protein response involves
Increased synthesis of chaperones
As they emerge from the ribosome, signal sequences are recognized and bound by a(n)
Signal recognition particle (SRP)
The term "paracrine signaling" refers to
Signaling between cells located close to each other
During replication, _______ stabilizes the unwound DNA template so it can be copied by the DNA polymerase
Single stranded DNA binding proteins
WHich statement best describes the mechanism of action of miRNAs in blocking expression of proteins?
Single-stranded miRNA in association with the RISC complex, binds to the complementary sequence in the 3' UTR of mRNAs, blocking translation and inducing degradation of the mRNA
The basis for muscle contraction is the
Sliding of myosin and actin fibers past each other
A PCR reaction does not require
Sodium dodecyl sulfate
In prokaryotes, sigma factors are necessary for
Specific binding to certain promoters
Which character is NOT necessary in a plasmid vector to facilitate successful cloning
Strong bacterial promoter
A mutation that causes a G-protein to lose its ability to hydrolyse bound GTP would be expected to have constitutively
Active alpha subunits
What is NOT a commonly observed consequence of the binding of a signaling molecule to its cell surface receptor?
Increased synthesis of the receptor
Which statement about transcription of ribosomal RNA is FALSE
TBP binds the TATA sequence in the promoter of the ribosomal gene
Passive transport across the membrane refers to
Transport in the energetically favorable direction
Why is telomerase important in cancer cells
Abnormal increases in telomerase activity can allow tumor cells to replicate telomeres and keep proliferating indefinitely
The mass of the nuclear pore complex is estimated to be
About 30 times that of a ribosome
The citric acid cycle consists of the oxidation of ______ to produce ______
Acetyl CoA; CO2, NADH, and FADH2
Which of the following is not a function of actin-binding proteins?
Incorporation of micro filaments into the extracellular matrix
What statement about cyclin B is FALSE?
It cycles between active and inactive states in the cell cycle
What is not a destination for vesicles leaving the Golgi apparatus?
Mitochondria
WHich of the following RNAs is RNA polymerase II NOT responsible for transcribing
tRNA
On a typical prokaryotic chromosome, one would find how many telomeres?
0
Approximately what percentage of the mitochondrial proteome is encoded by mitochondrial DNA
1.0%
What is the net yield of ATP molecules per molecule of glucose from glycolysis?
2
You have a piece of circular DNA that can be cut by the restriction nucleases Xhol and Smal. If you were to cut the DNA with both Xhol and Smal, how many fragments of DNA would you end up with?
2
A restriction enzyme with a four-base recognition site would cleave DNA with a statistical frequency of once every
256 bp
The percentage of the average human gene that encodes proteins is approximately
3%
Regarding PCR, place the following in correct order: 1. Annealing - Cool to allow primers to form hydrogen bonds with ends of target sequence 2. Extension - DNA polymerase adds nucleotides to the 3' ends of each primer 3. Denaturation - Heat briefly to separate DNA strands
3-1-2
How many replication origins are there in the human genome
30,000
The human genome is distributed among ____ chromosomes
46 chromosomes
If n represents one copy of single-stranded genomic DNA, then which of the following represents the amount of DNA in a typical cell at G2 of the cell cycle?
4n
Suppose that a gene has three exons and two introns in the following order: 5' exon 1 — intron 1 — exon 2 — intron 2 — exon 3 3' Which of the following could not result from alternative splicing in this gene?
5' exon 2 — exon 1 3'
How many molecules would be produced from two molecules of DNA following five rounds of PCR
64
Taken together, what is the total number of unique nucleotides in DNA and RNA?
8
What correctly describes a cDNA molecule?
A DNA copy of an RNA sequence synthesized by the enzyme reverse transcriptase
A pseudogene is
A gene that arose through gene duplication, but by acquiring mutations became nonfunctional
A molecule that is not membrane permeable binds to a membrane protein on the outside of a cell. This changes the conformation of the protein, causing the binding site to face the inside of the cell. The molecule is then released into the cell and the conformation of the binding site changes again so that it is outside the cell. This is what type of transporter?
A membrane carrier
The feature that most clearly discriminates eukaryotes from prokaryotes is the presence of ______ in eukaryotic cells
A nucleus
MRNA molecules are exported from the nucleus to the cytoplasm via
A recruited protein complex
Suppose an E. Coli cell is in an environment that is rich in glucose and poor in lactose. Which statement best explains gene expression of enzymes used in lactose breakdown?
A repression binds to the operator site of the lac operon and inhibits transcription of the genes involved in lactose breakdown
The ribosomes of the rough ER are targeted to the cytoplasmic side of the membrane via
A sequence within the protein being synthesized
Which statement about introns in the yeast Saccharomyces cervisae is true?
A small percentage of S. Cervesae genes contain introns, and these introns are usually located near the beginning of the gene
Some bacterial promoter regions are regulated by ____ that stimulate RNA polymerase binding and by _____ that block RNA polymerase binding
Activators; repressors
Dynesin and kinesin are similar in that they consist of heavy chains with globular heads which bind both ______ and _______
ATP; microtubules
Mutations in the internalization signal of endocytic receptors prevent their interaction with
Adaptor proteins
Which process both stabilizes and increases the efficiency of translation of an mRNA
Addition of a 7-methylguanosine cap
CAMP is synthesized from ATP by the action of
Adenylyl cyclase
Which statement about cis-acting elements is true?
All of the above
Estimates of mutation rates for a variety of genes indicate that the frequency of errors during replication is much lower than would be predicted on the basis of complementary base pairing. Which mechanisms account for the higher degrees of fidelity?
All of the above (conformational changes in DNA polymerase, 3' to 5' exonuclease activity of DNA polymerase, requirement of a primer for DNA synthesis by DNA polymerase)
Point mutations in DNA result from
All of the above (incorporation of incorrect bases during replication, changes as a result of chemical exposure, changes as a result of radiation exposure)
In the developing of an antibiotic, which of the following would be an effective strategy or target drug?
All of the above (inhibition of translational initiation, induction of premature polypeptide chain termination, inhibition of aminoacyl tRNA binding)
The human genome contains only 20,000 to 25,000 actual gene sequences, yet the human genome can produce up to 100,000 gene products. Which of the following processes accounts for this difference?
Alternative splicing
A feature common to most transmembrane proteins is
An a-helical region of approximately 20-25 hydrophobic amino acids
Which statement about exons is FALSE?
An exon may contain sequences for snoRNAs
Human disease caused by mutations in mitochondrial genomes
Are inherited from the mother
If a drug blocked the activity of mitochondrial inner membrane proteins Tim9 and Tim10, what would most likely not be found in the outer mitochondrial membrane?
B-barrel proteins
All of the following are general transcription factors used in eukaryotic transcription except
BRE
Which of the following RNAs is least stable and has the shortest half life?
Bacterial mRNAs
How does nucleotide-excision repair differ from base-excision repair?
Base-excision repair recognizes and removes single damaged bases, whereas nucleotide-excision repair is more general, recognizing many different lesions that distort the DNA molecule
Typically, nuclear localization signals are composed primarily of
Basic amino acids
MRNAs are degraded in the cytoplasm by
Both a and b (shortening of the poly-A tail and degradation from the 3' end; removal of the 5' cap and degradation from the 5' end)
Which of the following statements concerning elongation of DNA at the replication fork is false?
Both strands are synthesized continuously at the replication fork
The nuclear lamina associates with
Both the inner nuclear envelope membrane and chromatin
What is the function of cofilin in creating a dynamic cytoskeleton?
By cleaving actin filaments, which can lead to further polymerization or degradation of the filaments, which leads to a dynamic cytoskeleton
The signaling molecule nitric oxide (NO) functions
By diffusing across the cell membrane and changing the activities of intracellular enzymes
Which is not a type of histone modification used for controlling gene expression
C-terminal amidation
The major cation responsible for regulating actin-myosin contraction is
Calcium
The amino terminal presequence on proteins imported into the mitochondrial inner membrane is
Cleaved by mitochondrial matrix processing peptidase (MPP)
mutation in the MutS gene is most commonly associated with
Colorectal cancer
Which statement about the relative concentration of Na+ and K+ inside and outside the membrane of a typical mammalian cell is true?
Concentration of Na+ outside the cell is about 30 times higher than inside the cell, and the concentration of K+ inside the cell is 10-30 times higher than outside the cell
Which is a mechanism of histone change that is mediated by chromatin remodeling factors?
Conformational change of histone tertiary structure
Mitochondria differ from other organelles in that they
Contain their own genome
Which steroid hormones are NOT secreted by the gonads?
Corticosteroids
According to the central dogma of molecular biology, transcription of genetic information occurs via
DNA-dependent RNA synthesis
Which step is considered the final aspect of processing an RNA molecule?
Degradation in the cytoplasm
The response initiated by protein kinase A is terminated by
Dephosphorylation of phosphoproteins by protein phosphatase 1
The role of the sigma factor in prokaryote transcription is to
Direct RNA polymerase to bind to different promoter regions
The outer mitochondrial membrane contains proteins that
Direct translocation
Cofilin plays a role in the
Disassembly of actin filaments
Which statement about ABC transporters is FALSE?
Each member of the family is a Cl- channel
The outer nuclear membrane is contiguous with
Endoplasmic reticulum
Cells regulate gene expression to conserve which resource?
Energy
Cell cycle checkpoints ensure that complete genomes are transmitted to daughter cells. DNA damage checkpoints are found in all of the phases, except
M phase
The lumen of the ER is equivalent topologically to the
Extracellular space
After development, liver cells stop cycling and stay in G1 (T/F)
False
All molecules that are in the nucleus are transported by a process that requires GTP (True/False)
False
Avery, Macleod, and McCarty showed that one type of bacteria could be transformed into another type by the uptake of purified RNA. True/False
False
Polypeptides in the ER are usually larger than polypeptides synthesized from the same mRNA that have not entered the ER (T/F)
False
Ribosomal proteins are synthesized in the nucléoles and then assembled onto rRNAs (T/F)
False
The generation of ATP by the mitochondrial ATP synthase is an active transport process. True/False
False
Which statement about the glucose transporter is false?
Flow through it is unidirectional
Ran GAP association with cytoplasmic filaments of the nuclear pore results in the conversion of the nucleotide that is bound to nuclear Ran into
GDP
What is true regarding heterotrimeric G proteins in a resting state
GDP is bound to the a-subunit in a complex with both the B and y subunits
The junctions between animal cells that allow for free passage of molecules smaller than approximately 1000 daltons are called
Gap junctions
In polysaccharides, sugars are linked together by means of what kind of bonds?
Glycosidic bonds
Ribosomes contain one copy of each of 5.8S, 18S, 28S rRNA. The major mechanism ensuring that each is produced in equal molar amounts is the
Grouping of DNA in segments encoding each rRNA into a single rRNA gene
In nucleotide-excision repair of thymine dimers, what is the correct order of enzymatic activity, following damage recognition
Helices —> nuclease —> polymerase —> ligase
In the chromatin around centromeres, nucleosomes are present that have a unique structure in which the core protein ______ is replaced by _______, and this variant of the nucleosome is required for protein assembly at the kinetochore
Histon H3; CENP-A
Which of the following are not phosphorylation by the CdK1/cyclin B complex during mitosis?
Histone H3
The two strands of DNA in the double helix are held together by
Hydrogen bonds between the bases of each strand
In E. Coli, the major enzyme responsible for DNA replication is DNA polymerase
III
A reporter gene is used to
Identify regulatory sequences from the upstream regions of other genes
Transgenic mice carry a foreign gene
In all of their cells
Chromosomes are distributed in the nucleus
In distinct territories
A ribozymes is defined as an enzyme
In which an RNA molecule is responsible for the catalytic activity
The lac operon in E. Coli is regulated by lactose, which
Inactivates a repression of transcription
In proteins being made on rough ER, short spans of hydrophobic amino acids that form alpha helices
Induce a conformational change in the translocations, allowing them to exit the ER membrane
The nuclear basket protein complex is a component of the nuclear pore complex found
Inside the nucleus
What is an example of endocrine signaling?
Insulin release by B cells in the pancreas, mediating the effect of glucose uptake by muscle cells
What is not one of the four major classes of organic molecules in the cell?
Ions
One way that a promoter differs from an enhancer is that it
Is not located far away from the gene it regulates
In cell fractionation experiments in which sub cellular organelles are separated on the basis of their density, the smooth ER is _____ the rough ER
Lighter than
Which of the following are NOT compartments in the nucleus?
Lipid droplets?
WHich of the following transposable elements accounts for ~21% of the human genome?
Long interspersed elements (LINEs)
Which rationale best describes the ability of an enhancer to mediate transcription from very distant sites
Looping of the DNA can occur, allowing the transcription factor to come into the proximity of RNA polymerase
The lac operon is regulated by both a positive transcriptional control system and a negative transcriptional control system. Under what conditions will both systems operate to stimulate transcription of the lac operon?
Low glucose and high allolactose
During mismatch repair in E. Coli, the parental strand is recognized by
Methylated adenines
Which of the following will NOT solubilize a typical peripheral membrane protein
Mildly hypertonic saline
WHich statement about LINEs is FALSE?
Mutation induced by LINEs are exclusively harmful
What statement about LINEs is false?
Mutations induced by LINEs are exclusively harmful
Together, glycolysis and the citric acid cycle directly generate 2 molecules of ATP and 2 molecules of GTP. Most of the energy derived from the oxidation of glucose comes from the oxidation of the ______ generated from ________
NADH; the citric acid cycle
What class of amino acids is buried within the folded structure of the protein?
Non-polar
The human mitochondrial genome encodes only 22 tRNAs. This limited array of tRNAs can read 64 possible triplet corons through extreme wobble in base pairing at the third codon position and the use of a(n) ________ genetic code
Nonuniversal mitochondrial
The most prominent nuclear body is the
Nucleolus
Spliced mRNAs have protective mechanisms to prevent rapid degradation, but introns are rapidly degraded in the
Nucleus
Which of the following is not found in a nucleosome core particle
One molecule of H1 protein
What statement about protein kinase A is FALSE?
PKA binds a total of four molecules of cAMP, one on each of the four subunits
The ingestion of large particles by cells is a form of endocytosis known as
Phagocytosis
Which transport mechanism can bring whole cells into a cell
Phagocytosis
CREB is activated by
Phosphorylation by protein kinase A in the nucleus
Proteins with a C-terminal transmembrane sequence are
Posttranslationally brought to the ER by TRC40, where they remain in the ER membrane with their N-terminal domain facing the lumen
Which of the following is NOT a part of the transcription complex
RFC
The initiator codon in prokaryotes is
Recognized via the Shine-Dalgarno sequence
The nucléoles is the site where
Ribosomal RNA is transcribed and ribosomes are partially assembled
In the "pulse-chase" experiment, Palade and colleagues studied the pathway taken by newly secreted proteins in pancreatic avinât cells by labeling them with radioactive amino acids and then determining their progressive location within the cells. Which of the following represents the correct order from which the proteins were identified?
Rough ER —> Golgi aparratus —> secretory vesicles
You perform an experiment by incubating a radiolabeled nucleotide into the medium of a culture of cells. The cells that take up the radio label would be expected to be in what phase of the cell cycle?
S phase
When a striated muscle is stimulated to contract, calcium is released primarily from the
Sarcoplasmic reticulum
A major function of tight junctions is to
Seal the space between adjacent cells
Which of the following is NOT a contiguous membrane domain?
Secretory granules
Protein transport into the nucleus occurs by
Selective transport through nuclear pore complexes
Though Na+ is smaller than K+,, its passage through K+ channels is blocked by the ____ filter
Selectivity
Most mitochondrial genomes consist of
Several circular DNA molecules
DNA polymerase requires a primer and cannot initiate synthesis de novo. WHat serves as a primer for DNA replication?
Short fragments of RNA complementary to the template strand
Which statement about ion channels is true
THey are opened either by the binding of ligands or by changes in electric potential across the membrane
In some proteins, the only transmembrane sequence is located C-terminally in the protein. These proteins are recognized by
TRC40 (GET3)
Which molecule serves as an adaptor between amino acids and mRNA during translation
TRNA
A protein's alpha hélices and beta sheets fold together to create an overall shape at the _____ level of protein folding.
Tertiary
Cholesterol has a chemical structure similar to
Testosterone and estrogen
What statement about G protein signaling is FALSE?
The alpha subunit becomes deactivated when the protein dissociates from the receptor
Binding of SRP to the signal sequence arrests the further translation of the nascent polypeptide chain. How does the arrest of translation promote the subsequent translocation of the polypeptide chain through the Sec61 translocation complex?
The arrest of translation cause the polypeptide to move through the complex as the tRNA releases the new polypeptide chain allowing the complex
Partial digestion of chromatin with micrococcal nuclease was found to yield DNA fragments approximately 200 bp long. What accounts for this phenomenon?
The binding of proteins to DNA in chromatin protects regions of DNA from nuclease digestion
Peroxisomes are NOT involved in
The biosynthesis of catalase
What reaction will NOT result in water being formed as a product?
The cleavage of sucrose into fructose and glucose
Adherins junctions and des osmoses may be distinguished from each other on the basis of
The linkage of cadherins either to actin filaments or intermediate filaments respectively
What are some possible benefits of the evolution of a nucleus in eukaryotes?
The nucleus can filter which substances enter and leave due to the nuclear pores and the nuclear envelope
What is true of a peripheral membrane protein?
The protein can interact with hydrophilic portions of phospholipids
Whether a microtubule shrinks or grows is determined by
The rate of GTP-bound tubulin addition relative to the rate of tubulin GTP hydrolysis
Which statement about transcriptional termination in prokaryotes is FALSE
The ribosome comes to a UAA, UAG, or UGA stop codon, and transcription ceases
Voltage-sensitive K+ channels are 1000 times more permeable to K+ than to Na+ because
The selectivity filter removes the water molecules from K+ ions but not from Na+ ions
A KDEL sequence is necessary for
The transport of resident ER proteins from the Golgi to the ER
What statement about introns is true?
They are part of a gene, but they are absent from the corresponding mRNA
A member of the heat-shock class of proteins, BiP, is necessary for the proper folding of proteins in the ER, in terms of function, what do BiP and the heat shock proteins (HSP) have in common
They both protect the protein or polypeptide from extracellular environmental factors that may cause the protein to degrade
Which statement about pyrimidique dimers is FALSE?
They can be repaired by photoreactivation in human cells
Which statement describes centraméricain sequences in humans
They consist of A/T-rich-a-satellite DNA, spanning 1-5 million base pairs
How are lncRNAs similar to miRNAs?
They correspond to non coding regions of the genome
G protein-coupled receptors are important molecules involved in signal transduction. Which statements about G protein-coupled receptors is true?
They generally contain seven membrane spanning alpha helices
Which statement is true of all known DNA polymerases
They synthesize DNA in the 5' to 3' direction, and they require a preformed primer hydrogen-bonded to the template
Which statement about introns is true?
Though they are part of a gene, they are absent from the corresponding mRNA
What is NOT a protein translon/transolcase found in the mitochondrial inner or outer membrane?
Toc75
The twisting of the parental DNA strands around each other ahead of a replication fork is relieved by enzymes called
Topoisomerases
RNA is copied from DNA through a process called
Transcription
The role of cytochrome c in the electron transport chain is to
Transfer electrons from complex III to complex IV
The process by which proteins are made from RNA templates is called
Translation
What process does NOT take place in the nucleus?
Translation
Christian Anfisen and colleagues showed that proteins contain all the information to spontaneously fold into an active enzyme. Yet sixty years later, we can still not predict the 3-D shape of a protein from its amino acid sequence. True/false?
True
Nucleosides are an impediment to transcription in eukaryotic cells (True/False)
True
The progression from metaphase to anaphase is triggered by
Ubiquitin-mediated proteolysis of key proteins
Deamination of cytosine results in the conversion of cytosine to
Uracil
What is NOT involved in protein transport into mitochondria?
Vesicular transport
The directionality of nuclear protein import is determined by
an unequal distribution of Ran/GTP
Glucose repression is mediated by several positive transcriptional control mechanisms. What is NOT one of those mechanisms?
cAMP-activated CAP transcribes genes that metabolize lactose
Two examples of membrane lipids that are present in small amounts are
glycolipids and phosphatidylinositol.
THe ENCODE project revealed that as much as 75% of the human genome is actually transcribed into RNA. Most of this is non-protein coding RNA. WHich of the following include two new classes of non coding RNA discovered by the ENCODE project?
microRNA and lncRNA
The enzyme that synthesizes DNA using RNA templates is called
reverse transcriptase
What statement regarding tRNAs is FALSE?
tRNAs differ in sequence only at the anticodon
