Chapter 9 (book)

Question 1

Which of the following are features of transcription in eukaryotes only?

Answer 1

Presence of multiple types of RNA polymerases
Addition of 5’ cap to mRNA
Alternative splicing of transcripts can produce multiple types of polypeptides

Question 2

To begin each round of elongation during translation, the tRNA carrying the next amino acid to be added to the polypeptide chain binds to the [] site of the ribosome

Answer 2

A or aminoacyl

Question 3

During elongation in prokaryotic cells, which proteins bring tRNAs into the A site?

Answer 3

Elongation factors

Question 4

In order to initiate translation, a eukaryotic small ribosomal subunit must first bind the 5’ cap and then scan the 5’ UTR until it locates the start codon. This feature of translation explains why eukaryotic mRNAs ______.

Answer 4

are monocistronic

Question 5

features of transcription in prokaryotes only

Answer 5

A single type of RNA polymerase
The promoter consists of a -35 and a -10 sequence
A single mRNA contains multiple polypeptide start sites

Question 6

During translation in prokaryotes, each round of elongation begins when a tRNA carrying the next amino acid to be added to the polypeptide, binds to the ____.

Answer 6

A site on the ribosome

Question 7

Crick and Brenner performed experiments using combinations of bacteriophage mutations. If a single nucleotide deletion (–) occurred, which additional mutations or combinations of mutations could suppress the mutant phenotype?

Answer 7

single nucleotide insertion (+)

two single nucleotide deletions (– –)

Question 8

What feature of eukaryotic translation requires that eukaryotic mRNAs be monocistronic?

Answer 8

The small ribosomal subunit must bind the 5’ cap and scan the 5’ UTR until it finds the initiator codon.

Question 9

To decipher the genetic code, an in vitro translation system containing cellular extracts with ribosomes, tRNAs, enzymes and radioactive amino acids was used to ______.

Answer 9

synthesize radioactively-labeled polypeptides from synthetic messenger RNAs

Question 10

If transcription is proceeding to the right, which of these would be the correct representation of the conventional system used by geneticists to number nucleotides in a gene?

Answer 10

-5 -4 -3 -2 -1 +1 +2 +3 +4 +5
Since, the question states that transcription proceeds to the right, the numbering of nucleotides to the left of the transcriptional start site should use negative numbers.

Question 11

Enzymes known as [] -tRNA [] are responsible for attaching amino acids to their corresponding tRNAs.

Answer 11

Aminoacyl; synthetases

Question 12

For some amino acid positions, Yanofsky identified multiple missense mutations that resulted in a change in the amino acid. For example, in tryptophan synthase, the sequence GGA codes for a glycine at position 211. Mutation to AGA causes an arginine at this position. Mutation to GAA results in a glutamic acid. Neither of these mutants is able to survive in the absence of tryptophan. Yanofsky found that he could recombine these mutations, resulting in

Answer 12

GGA recombinants that could survive in the absence of tryptophan.

Question 13

By convention, how is the first nucleotide transcribed by RNA polymerase labeled?

Answer 13

+1

Question 14

Spliceosome

Answer 14

Introns are removed using two sequential cuts.

Question 15

The function of an aminoacyl-tRNA synthetase enzyme is to catalyze the ______.

Answer 15

attachment of an amino acid to its appropriate tRNA

Question 16

Yanofsky found that recombination between two mutations that altered the same amino acid could restore a wild-type phenotype. For example, in tryptophan synthase, the sequence GGA codes for a glycine at position 211. Mutation to AGA causes an arginine at this position. Mutation to GAA results in a glutamic acid. Neither of these mutants can survive in the absence of tryptophan (trpA–). Recombination between these two mutants yields trpA+ (GGA) recombinants. What conclusion about the genetic code do these data support?

Answer 16

A codon is composed of more than one nucleotide.

Question 17

Used in prokaryotic translation but not in eukaryotic translation

Answer 17

Shine-Dalgarno sequence to facilitate mRNA binding to the small ribosomal subunit
tRNAifMet as the initiator tRNA
Coupling of transcription and translation

Question 18

steps in the splicing of primary transcripts via a spliceosome

Answer 18

5’ splice is cut
A lariat is formed
3’ splice is cut
Two exons are joined together

Question 19

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 _____.

Answer 19

genetic code

Question 20

Which sequences of bacterial promoters are particularly important for transcription initiation?

Answer 20

The -10 site with a consensus sequence of 5’ TATAAT 3’

The -35 site with a consensus sequence of 5’ TTGACA 3’

Question 21

Wobble

Answer 21

The ability of a single tRNA to recognize more than one codon

Question 22

In ______ cells, the initiator tRNA carries the amino acid N-formylmethionine.

Answer 22

Prokaryotic

Question 23

antimorphic mutations (or alleles)

Answer 23

block the activity of wild-type alleles of the same gene, causing a loss of function even in heterozygotes. (Synonymous with dominant-negative mutations.)

Question 24

poly-A tail

Answer 24

modification that occurs at the 3’ end of eukaryotic mRNAs
the 3’ end of eukaryotic mRNA, consisting of 100–200 A residues, that stabilizes the mRNA and increases the efficiency of translation initiation.
Serves to: enhance the efficiency of translation; to increase the stability of the mRNA in the cytoplasm

Question 25

Splice Donor

Answer 25

nucleotide sequences in a primary transcript at the border between an intron and the upstream exon that precedes it; required for RNA splicing. At the 5' end of intron

Question 26

splice acceptors

Answer 26

nucleotide sequences in a primary transcript at the border between an intron and the downstream exon that follows it; required for RNA splicing. At the 3' end of the intron

Question 27

branch sites

Answer 27

special base sequences of RNA nucleotides within an intron that helps form the lariat intermediate required for RNA splicing. An A that bonds to the 5' end of the intron

Question 28

function of an aminoacyl-tRNA synthetase enzyme

Answer 28

attachment of an amino acid to its appropriate tRNA

Question 29

amorphic, or loss-of-function

Answer 29

A mutation that completely abolishes the function of a gene

Question 30

In what type of cell do the terms transcript and mRNA refer to the same molecule?

Answer 30

In a bacterium

Question 31

intragenic suppression

Answer 31

The restoration of function by a second mutation at a different site in the same gene

Question 32

Frameshift mutation

Answer 32

The addition or deletion of a number of bases that is not a multiple of 3

Question 33

A loss-of-function allele that results in a complete lack of gene function is a ____.

Answer 33

null allele

Question 34

In bacteria, the term open promoter complex refers to the small bubble-like structure that forms ____.

Answer 34

during the initiation phase of transcription

Question 35

closed promoter complex

Answer 35

Transcription in E. coli is initiated when the sigma factor of the RNA polymerase holoenzyme binds to the promoter region to form a

Question 36

Mutation in the 3' UTR

Answer 36

mutation in a noncoding region that can affect the rate of translation of an mRNA

Question 37

A missense mutation that changes the properties of a single amino acid in a protein is a

Answer 37

nonconservative substitution.

Question 38

Primary transcript

Answer 38

The first transcript produced from protein-encoding genes of eukaryotes is a long molecule

Question 39

Capping

Answer 39

The addition of a methylated "backward G" to the 5' end of a eukaryotic mRNA

Question 40

The RNA-like strand of DNA is also called the coding strand because it _____.

Answer 40

has the same polarity and sequence as the mRNA but with T's instead of U's

Question 41

Introns

Answer 41

Intervening sequences of DNA that are not represented in mature mRNA

Question 42

Describes the presence of exons and introns in protein-coding genes in eukaryotes

Answer 42

While most protein-coding eukaryotic genes have introns, a few have none.

Question 43

Open promoter complex

Answer 43

the complex of RNA polymerase holoenzyme bound to an unwound template strand of DNA during the initiation phase of transcription

Question 44

coding strand

Answer 44

For protein-encoding genes, the RNA-like strand

Question 45

describe variations in the sizes and numbers of introns in eukaryotic organisms

Answer 45

A gene can have none or many introns and introns can be short or very long (hundreds of kilobases long).

Question 46

The RNA-like strand of DNA is also called the coding strand because it _____.

Answer 46

has the same polarity and sequence as the mRNA but with T's instead of U's

Question 47

ribozyme

Answer 47

An RNA molecule that has catalytic activity

Question 48

In mammals, what process is used to produce two types of antibodies (secreted and membrane-embedded) in a B cell?

Answer 48

Alternative splicing

Question 49

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

Answer 49

Anticodon

Question 50

following must bind to an aminoacyl-tRNA synthetase enzyme in order to charge a transfer RNA with an amino acid

Answer 50

ATP A specific transfer RNA A specific amino acid

Question 51

During translation, which base of the codon can be mismatched with an anticodon base on the tRNA?

Answer 51

Third base of the codon

Question 52

In order to charge a tRNA, ATP, a specific transfer RNA and a specific amino acid all bind to which enzyme?

Answer 52

Aminoacyl-tRNA synthetase

Question 53

The RNA-like strand of DNA is also called the coding strand because it _____.

Answer 53

has the same polarity and sequence as the mRNA but with T's instead of U's

Question 54

The amino acid phenylalanine is specified in the genetic code as UUPy. If a cell uses a single tRNA for phenylalanine, that tRNA should be able to recognize _____.

Answer 54

only U or C at the 3' end of a codon that starts with UU

Question 55

Site of aminoacyl-tRNA binding

Answer 55

A site

Question 56

Site that contains a tRNA with an attached peptide

Answer 56

P site

Question 57

Site where an uncharged tRNA leaves the ribosome

Answer 57

E site

Question 58

From crystallization studies, it has been shown that the component making up most of the mass in the central part of the ribosome is the ribosomal []

Answer 58

RNA

Question 59

The component of peptidyl transferase that catalyzes the transfer of the polypeptide in the P site to the amino acid in the A site is a [] in the 50S unit

Answer 59

Ribozyme

Question 60

Polyribosome

Answer 60

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

Question 61

How does the speed of translation compare between eukaryotes and prokaryotes?

Answer 61

The speed of translation is generally higher in prokaryotes.

Question 62

possible posttranslational modifications

Answer 62

Addition of a carbohydrate Addition of ubiquitin Addition of a phosphate group

Question 63

During translation, transfer RNAs bind to ______ specific regions on the ribosome, called the ______.

Answer 63

three; P, A and E sites.