Chapter 7

Question 1

List three ways in which the process of eukaryotic transcription differs from the process of bacterial transcription.

Answer 1

Any three of the following are acceptable. 1. Bacterial cells contain a single RNA polymerase, whereas eukaryotic cells have three. 2. Bacterial RNA polymerase can initiate transcription without the help of additional proteins, whereas eukaryotic RNA polymerases need general transcription factors. 3. In eukaryotic cells, transcription regulators can influence transcriptional initiation thousands of nucleotides away from the promoter, whereas bacterial regulatory sequences are very close to the promoter. 4. Eukaryotic transcription is affected by chromatin structure and nucleosomes, whereas bacteria lack nucleosomes.

Question 2

Name three covalent modifications that can be made to an RNA molecule in eukaryotic cells before the RNA molecule becomes a mature mRNA.

Answer 2

A poly-A tail is added. A 5′ cap is added. Introns can be spliced out.

Question 3

In eukaryotic cells, general transcription factors are required for the activity of all promoters transcribed by RNA polymerase II. The assembly of the general transcription factors begins with the binding of the factor _____ to DNA, causing a marked local distortion in the DNA. This factor binds at the DNA sequence called the ____ box, which is typically located 25 nucleotides upstream from the transcription start site. Once RNA polymerase II has been brought to the promoter DNA, it must be released to begin making transcripts. This release process is facilitated by the addition of phosphate groups to the tail of RNA polymerase by the factor _____.

Answer 3

TFIID; TATA; TFIIH

Question 4

The genetic code specifies which amino acids are encoded by the codons on the mRNA. It is _________ because some amino acids have more than one codon. ____________ codons do not specify an amino acid.

Answer 4

redundant; STOP

Question 5

12. Which of the following is not a key advantage of wobble in the codon-anticodon reaction? a. It allows for fewer tRNAs in the cell. b. It allows for making more than one protein from the same coding sequence. c. It allows for a certain amount of mutation in the mRNA without affecting the protein sequence. d. All of these are advantages of wobble.

Answer 5

b

Question 6

The _______________ in a tRNA molecule is designed to base-pair with a complementary sequence of three nucleotides, the ________________, in an mRNA molecule.

Answer 6

anticodon; codon

Question 7

In all cells, a special_____molecule, recognizing the ___________codon AUG and carrying the amino acid ______________, provides the amino acid that begins a protein chain.

Answer 7

initiator tRNA; start; Met_( methionine)

Question 8

15. Which of the following pairs of codons might you expect to be read by the same tRNA as a result of the wobble? (a) CUU and UUU (b) GAU and GAA (c) CAC and CAU (d) AAU and AGU

Answer 8

c These two codons differ only in the third position and also encode the same amino acid, which is the definition of wobble.

Question 9

The piece of RNA below includes the region that codes the binding site for the initiator tRNA needed in translation. 5′-GUUUCCCGUAUACAUGCGUGCCGGGGGC-3′ Which amino acid will be on the tRNA that is the first to bind to the A-site of the ribosome? (a)methionine (b)arginine (c)cysteine (d)valine

Answer 9

(a)methionine

Question 10

Once an mRNA is produced, its message can be decoded on ribosomes. The ribosome is composed of two subunits: the ________ subunit, which catalyzes the formation of the peptide bonds that link the amino acids together into a polypeptide chain, and the __________ subunit, which matches the tRNAs to the codons of the mRNA.

Answer 10

large; small

Question 11

During the chain elongation process of translating an mRNA into protein, the growing polypeptide chain attached to a tRNA is bound to the ____ site of the ribosome. An incoming aminoacyl-tRNA carrying the next amino acid in the chain will bind to the ________ site by forming base pairs with the exposed codon in the mRNA.

Answer 11

P; A

Question 12

The _____ enzyme catalyzes the formation of a new peptide bond between the growing polypeptide chain and the newly arriving amino acid.

Answer 12

peptidyl transferase

Question 13

The end of a protein-coding message is signaled by the presence of a stop codon, which binds the __________________ called ____.

Answer 13

protein; release factor.

Question 14

Eventually, most proteins will be degraded by a large complex of proteolytic enzymes called the _____.

Answer 14

proteasome

Question 15

The instructions specified by the DNA will ultimately specify the sequence of proteins. This process involves DNA, made up of ___ different nucleotides, which gets ____into RNA, which is then ________ into proteins, made up of _____ different amino acids.

Answer 15

4; transcribed; translated; 20

Question 16

In eukaryotic cells, DNA gets made into RNA in the _______, while proteins are produced from RNA in the _____.

Answer 16

nucleus; cytoplasm

Question 17

The segment of DNA called a ____ is the portion that is copied into RNA; this process is catalyzed by RNA _____.

Answer 17

gene; polymerase

Question 18

Where does transcription take place?

Answer 18

nucleus

Question 19

Where does translation take place?

Answer 19

cytoplasm/ribosome

Question 20

Where does RNA splicing take place?

Answer 20

nucleus

Question 21

Where does polyadenylation take place?

Answer 21

nucleus

Question 22

Where does RNA capping take place?

Answer 22

nucleus

Question 23

Unlike DNA, which typically forms a helical structure, different molecules of RNA can fold into a variety of three-dimensional shapes. This is largely because ___________________.

Answer 23

RNA is ss

Question 24

For a cell’s genetic material to be used, the information is first copied from the DNA into the nucleotide sequence of RNA in a process called ___ ____.

Answer 24

transcription

Question 25

Various kinds of RNA are produced, each with different functions. _____ molecules code for proteins, _________ molecules act as adaptors for protein synthesis, ________ molecules are integral components of the ribosome, _________ molecules regulate gene expression, and _______other __________ molecules are important in the splicing of RNA transcripts, gene regulation, telomere maintenance, and many other processes.

Answer 25

mRNA; tRNA; rRNA; microRNAs; noncoding RNAs

Question 26

Imagine that an RNA polymerase is transcribing a segment of DNA that contains the following sequence: 5′-AGTCTAGGCACTGA-3′ 3′-TCAGATCCGTGACT-5′ If the polymerase is transcribing from this segment of DNA from left to right, which strand (top or bottom) is the template?

Answer 26

bottom

Question 27

Imagine that an RNA polymerase is transcribing a segment of DNA that contains the following sequence: 5′-AGTCTAGGCACTGA-3′ 3′-TCAGATCCGTGACT-5′ What will be the sequence of that RNA (be sure to label the 5′ and 3′ ends of your RNA molecule)?

Answer 27

5’-AGUCUAGGCACUGA-3’

Question 28

Most rRNA genes are transcribed by which main polymerase?

Answer 28

RNA Polymerase I

Question 29

tRNA genes are transcribed by which main polymerase?

Answer 29

RNA Polymerase III

Question 30

5S rRNA genes are transcribed by which main polymerase?

Answer 30

RNA Polymerase III

Question 31

protein-coding genes are transcribed by which main polymerase?

Answer 31

RNA Polymerase II

Question 32

miRNA genes are transcribed by which main polymerase?

Answer 32

RNA Polymerase II

Question 33

The genetic code specifies which amino acids are encoded by the codons on the mRNA. It is _________ because some amino acids have more than one codon. ____________ codons do not specify an amino acid.

Answer 33

redundant; STOP

Question 34

Which of the following pairs of codons might you expect to be read by the same tRNA as a result of wobble?

1. 5’-AGA-GGA-GAU-3’
2. 5’-ACA-CCC-ACU-3’ (Thr- Pro-Thr)
3. 5’-GGG-AAA-UUU-3’ (GLy-Lys-Phe)
4. 5’-CGG-GGU-GAC-3’(Arg-Gly-Asp)

Answer 34

a

Question 35

1. Which of the following pairs of codons might you expect to be read by the same tRNA as a result of wobble?
   (a) CUU and UUU
   (b) GAU and GAA
   (c) CAC and CAU
   (d) AAU and AGU

Answer 35

c

These two codons differ only in the third position and also encode the same amino acid, which is the definition of wobble.

Question 36

_____ produces an RNA molecule that is complementary strand of DNA.

Answer 36

transcription

Question 37

The sequence of the coding strand is equivalent to the ______.

Answer 37

RNA products

Question 38

_______ mediate transcription.

Answer 38

RNA Polymerase

Question 39

The growing RNA chain is extended in the ___ to ___ direction.

Answer 39

5’; 3’

Question 40

What is responsible for both unwinding the RNA helix and catalyzing the formation of the phosphodiester bonds between nucleotides.

Answer 40

RNA Polymerase

Question 41

What type of RNA codes for proteins?

Answer 41

mRNA

Question 42

What type of RNA forms the core of the ribosome’s structure and catalyze protein synthesis?

Answer 42

rRNA

Question 43

What type of RNA regulate gene expression?

Answer 43

miRNA

Question 44

What type of RNA serve as adaptors between mRNA and amino acids during protein synthesis?

Answer 44

tRNA

Question 45

What type of RNA is used in RNA splicing, gene regulation, telomere maintenance, and many other processes?

Answer 45

Other noncoding RNAs

Question 46

What is required for RNA Pol II to initiate?

Answer 46

General transcription factors