Genetics Translation

Question 1

All amino acids have a […] an […], and a […]. An enzyme of the ribosome catalyzes formation of a […] between the carboxyl group of one amino acid and the amino group of the next
The […] of each amino acid is distinct; some are not charged, some are polar, and some are […].

Answer 1

central carbon; an amino group; carboxyl group; peptide bond; R-group; electrically charged

Question 2

Polypeptides are strings of […] that are assembled by ribosomes. Ribosomes are “machines” that contain multiple […] and proteins. Ribosomes translate mRNA in the […] direction, reading each triplet codon and assembling the amino acids in the order specified by the codons. Specific tRNAs bound to amino acids (charged tRNAs) […] the appropriate amino acid into the ribosome

Answer 2

amino acids; ribosomal RNAs; 5′-to-3′; deliver

Question 3

Ribosomes in bacteria, archaea, and eukaryotes perform three tasks: Bind [..] and identify the start codon, where translation begins, Facilitate complementary base pairing of […] and the corresponding tRNA anticodons. Catalyze formation of peptide bonds between amino acids on the growing […].

Answer 3

mRNA; mRNA codons; polypeptide chain

Question 4

Ribosome composition—number and sequence of […] molecules and number and type of proteins—differs between bacteria, archaea, and eukaryotes. Ribosomes are composed of two subunits, the […] ribosomal subunit and the [..] ribosomal subunit. Ribosomal subunit size is measured in […] units (S), a property based on size, shape, and hydration state

Answer 4

rRNA; large; small; Svedberg

Question 5

The […] site (P site) holds the tRNA to which the polypeptide is attached. The […] site (A site) binds a new tRNA molecule containing an amino acid to be added to the growing polypeptide chain. The […] site (E site) provides an avenue for exit of the tRNA after its amino acid has been added to the chain. The large subunit contains a channel from which the polypeptide chain […].

Answer 5

peptidyl; aminoacyl; emerges

Question 6

Translation can be divided into three phases: […], […], […]. The phases are similar in bacteria and eukaryotes, though there are several […]. The differences lie largely in how the […] is identified when translation is initiated

Answer 6

Initiation; Elongation; Termination; differences; start codon

Question 7

Initiation begins when the [….] binds near the 5′ end of the mRNA and identifies the start codon. The initiator tRNA, carrying the first […] of the polypeptide, binds to the start codon
Finally, the large subunit joins the small subunit to form the intact ribosome and […] begins.

Answer 7

ribosomal subunit; amino acid; translation begins

Question 8

[…] factor proteins help control ribosome formation and binding of the initiator tRNA. GTP provides the energy for […]. tRNAs used during translation that carry an amino acid are called […] tRNAs, whereas tRNAs without amino acids attached are uncharged.

Answer 8

Initiation; initiation; charged

Question 9

The preinitiation complex forms when the 16S rRNA and the […] sequence on the mRNA base pair. The Shine–Dalgarno sequence is a […] sequence of about six nucleotides located three to nine nucleotides upstream of the start codon. A complementary pyrimidine-rich sequence is found near the 3′ end of the 16S […]. For most of initiation, the 30S subunit is affiliated with an […], IF3, which prevents the 30S subunit from binding the 50S subunit

Answer 9

Shine–Dalgarno; purine-rich; rRNA; initiation factor

Question 10

The initiator tRNA binds to the start codon where the […] will be once the ribosome is fully assembled. Initiator tRNA carries a modified […], N-formylmethionine (f Met); the charged. initiator t R N A is called […]. IF2 and GTP help facilitate binding of […]. IF1 joins the […]. Together these form the […] initiation complex.

Answer 10

P site; amino acid; tRNA fmet; complex; 30S

Question 11

In the last stage of initiation, the 50S subunit joins the 30S subunit to form the intact […] . The union of the two subunits is driven by […] of GTP to GDP. The dissociation of IF1, IF2, and IF3 accompanies the joining of the subunits to create the 70S […] complex

Answer 11

ribosome; hydrolysis; initiation

Question 12

The correct start codon (A U G) can be located because it is embedded in a […]: 5’-ACCAUGG-3’. This sequence is called the […] sequence, after its discoverer, Marilyn Kozak. Location of the start codon leads to recruitment of the 60S subunit to the complex, using energy from […], and the dissociation of the e I F proteins.

Answer 12

consensus sequence; Kozak; GTP hydrolysis

Question 13

Elongation begins with recruitment of […] (E F) proteins and uses energy of GTP hydrolysis to: Recruit charged tRNAs to the […]. Form […] between sequential amino acids. Translocate the ribosome in the […] direction along the mRNA.

Answer 13

elongation factor; A site; peptide bonds; 3′

Question 14

Several different EFs and other ribosomal proteins carry out […] in a series of steps. EF-Tu and GTP carry charged tRNAs to the […]; the tRNA with the correct […] sequence pairs with the codon. When a tRNA pairs with the […] codon, hydrolysis of GTP releases EF-Tu-GDP from tRNA. […] catalyzes peptide bond formation between amino acids at the P and A sites, elongating the polypeptide and transferring it to the tRNA at the […].

Answer 14

elongation; anticodon; mRNA; Peptidyl transferase; A site

Question 15

The tRNA from the P site then exits through the [..]. EF-G translocates the ribosome, using GTP hydrolysis, moving it […] nucleotides toward the 3′ end of the m R N A. This moves the t R N A at the [..] to the [..] and opens the A site for the next charged t R N A carrying the correct anticodon.

Answer 15

E site; three; A site; P site

Question 16

Distinct elongation factors carry out elongation in […] and archaea and the steps are similar to those of bacteria. Based on sequence, archaeal and eukaryotic […] are more alike than archaeal and bacterial E Fs. This sequence comparison reinforces the conclusion that eukaryotes and archaea are more […] to one another than either is to bacteria.

Answer 16

eukaryotes; EF homologs; closely related

Question 17

The elongation cycle continues until one of the three stop codons (U A A, U A G, U G A) enters the […] of the ribosome. All organisms use […] to bind a stop codon in the A site. The polypeptide bound to the t R N A at the […] is then released while the RF is ejected and the ribosomal subunits separate.

Answer 17

A site; release factors; P site

Question 18

In bacteria, the release factor […] recognizes UAG and UAA and […] recognizes UAA and UGA, while […] recycles RF1. Eukaryotic and archaeal termination is accomplished by a single release factor […] in eukaryotes and a RF1 in archaea, each of which recognizes all three stop codons
Eukaryotes have a […] release factor that recycles e R F 1

Answer 18

RF1; RF2; RF3; eRF1; second

Question 19

Cell biologists estimate that each bacterial cell contains about […] ribosomes, collectively accounting for 25% of the mass of the cell
[…] micrographs reveal structures called polyribosomes, containing groups of ribosomes all actively translating the same […].

Answer 19

20,000; Electron; m R N A

Question 20

Each polypeptide-producing gene in eukaryotes produces […] mRNA, an RNA that directs synthesis of a single kind of polypeptide. Groups of bacterial and archaeal genes, called […], often share a single promoter and produce polycistronic m R N As that lead to synthesis of several different proteins
The genes of operons function in the same […] pathway and are regulated as a unit.

Answer 20

monocistronic; operons; metabolic

Question 21

[…] m R N As contain multiple polypeptide-producing segments, each with a start and stop codon. In bacterial and all but leaderless archaeal mRNAs, most translation-initiating regions contain a […] site. An […] spacer sequence that is not translated separates the segments. When the spacer sequences are short (a few nucleotides long), intact ribosomes may proceed to the next start codon after finishing […] of the previous segment

Answer 21

Polycistronic; Shine–Dalgarno; intercistronic; translation

Question 22

The term […] describes the correspondence between m R N A codon sequences and the amino acid sequences of the resulting polypeptides
Transfer R N As are […] molecules that interpret and then act on information carried in m R N A
They have [….] complementary to m R N A codons

Answer 22

“genetic code”; adaptor; anticodon sequences

Question 23

Groups of three consecutive nucleotides (codons) in an m R N A each correspond to […] amino acid
The genetic code contains […] different codons; with only […] common amino acids, this leads to redundancy—some amino acids are specified by more than […] codon

Answer 23

one; 64; 20; one

Question 24

The […] , with 64 combinations, provides enough variety to code 20 amino acids. 61 codons specify […], and 3 are stop codons. All amino acids except methionine and tryptophan are specified by at least two codons, called […] codons

Answer 24

triplet genetic code; amino acids; synonymous

Question 25

t R N A molecules with different anticodons for the same amino acids are called […] t R N As. Though there are 61 different codons that specify amino acids, most […] have 30 to 50 different t R N A genes. A relaxation of the strict complementary base-pairing rules at the third base of the codon is called […]

Answer 25

isoaccepting; genomes; third-base wobble

Question 26

Most synonymous codons can be grouped into pairs that differ only in the […]; the pairs either both carry a [..] (A or G) or both carry a pyrimidine (C or U). Third-base wobble occurs through […] pairing at the 3’ most nucleotide of the codon and the 5’ most nucleotide of the anticodon. However, a pyrimidine must still base-pair with a […]

Answer 26

third base; purine; flexible; purine

Question 27

In all organisms from bacteria to humans, the process of […] is similar
Because the genetic code is […], bacteria can be used to produce important proteins from plants and animals. However, there are a few exceptions to the universality of the genetic code, found principally in […], though there are three exceptions in nuclear D N A

Answer 27

translation; universal; mitochondria

Question 28

t R N A molecules are transcribed from […]. Correct charging of each t R N A molecule is […] for the integrity of the genetic code. Enzymes called […] or t R N A synthetases catalyze the addition of the correct amino acid to t R N As
Recognition of the isoaccepting tRNAs by the enzyme is complex with no single set of […].

Answer 28

t R N A genes; crucial; aminoacyl-t R N A synthetases; rules

Question 29

The production of […] is not complete until polypeptides are folded into their functional tertiary or quaternary structures. These steps involve formation of certain […], possible chemical modification, and other modifications followed by sorting and transport of proteins to their final destinations. […]polypeptide processing may include a variety of different steps

Answer 29

functional proteins; chemical bonds; Posttranslational

Question 30

The […] of one or more amino acids from a polypeptide is a common form of posttranslational polypeptide processing. For example, fMet is not found in functional […] proteins, nor is methionine always the first amino acid in eukaryotic proteins. The absence of these from the […] of proteins is due to their removal after translation

Answer 30

removal ; bacterial; N-terminus

Question 31

One of the most common amino acid modifications is […] , carried out by kinases. This modification can activate or inactivate a […]. Other enzymes may add methyl, hydroxyl, or acetyl groups to […]. […] side chains are also added to some proteins

Answer 31

phosphorylation; protein; amino acids; Carbohydrate

Question 32

Signal sequences of about 15 to 20 amino acids at the N-terminal end directs proteins to their […]. The […] suggests a mechanism by which proteins are transported to their correct locations. It proposes that the first 15 to 20 amino acids of many polypeptides contain an […] that directs proteins to their correct locations
[…] suggested that the signal sequence directs proteins to the endoplasmic reticulum (E R) and then the Golgi apparatus, where they are sorted for their specific destinations

Answer 32

cellular destinations; signal hypothesis; “address label”; Blobel

Question 33

Proteins destined to remain in the cell are typically translated at […] ribosomes in the cytoplasm
Polypeptides destined for […] are produced at the rough E R

Answer 33

“free”; secretion

Question 34

A remarkable set of experiments in the […] deciphered the genetic code and answered the following questions: Do […] codons overlap one another? How many nucleotides make up an […] codon? Is the polypeptide-coding information of m R N A […] or does it contain gaps?

Answer 34

1960s; neighboring; m R N A; continuous

Question 35

In 1964, [..] and […] used mini-RNAs just three nucleotides long (one for each possible codon) to resolve the ambiguities of previous experiments
They added the mini-RNAs (one type per experiment) to […] translation systems—each system contained all amino acids with one of these labeled with 14C. They isolated the ribosome–t R N A–m R N A complexes and determined which mini-R N A was associated with each labeled […]

Answer 35

Nirenberg; Leder; in vitro; amino acid

Question 36

Nirenberg and Leder tested all […] possible codons. They identified all 61 of the […] associations. They also identified the three stop codons, […], […], & […].

Answer 36

64; codon–amino acid; U A A, U A G, and U G A