Chapter 17 Questions Flashcards Preview

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Flashcards in Chapter 17 Questions Deck (59)

Who formulated the one gene–one enzyme hypothesis?

Beadle and Tatum


Genetic information of eukaryotic cells is transferred from the nucleus to the cytoplasm in the form of _____.



Which of the following statements is true?

Each amino acid in a protein is coded for by three bases in the DNA.


When RNA is being made, the RNA base _____ always pairs with the base _____ in DNA.

U ... A

-In RNA uracil takes the place of thymine


Generally speaking, how many genetic codes are there?



What mRNA codon would be made from the DNA triplet CGT?



The number of nucleotide bases "read" together on the mRNA to designate each amino acid is _____; this unit is called a(n) _____.

three ... codon


The codons AAA, CCC, GGG, and UUU specify the amino acids lysine, proline, glycine, and phenylalanine, respectively. What peptide sequence would be encoded by the sequence 5'-CCCAAATTTGGG-3', if present in the coding strand of the DNA?



How many nucleotides are needed to code for a protein with 450 amino acids?

at least 1,350


In many cases, more than one codon codes for the same amino acid. Because of this, we say that the code is _____.



Bacteria can transcribe and translate human genes to produce functional human proteins because _____.

the genetic code is nearly universal

- All organisms use the same genetic code, so it is possible (and the basis of many biotech applications) to produce human proteins using another organism's protein synthesis machinery.


In a eukaryotic cell, transcription takes place _____.

in the nucleus


Which of the following best describes the arrangement of genetic information in a DNA molecule?

The three-nucleotide words of a gene are arranged in a nonoverlapping series on the DNA template strand.


At one point, as a cell carried out its day-to-day activities, the nucleotides GAT were paired with the nucleotides CUA. This pairing occurred _____.

during transcription


Which of the following catalyzes the linkage between ribonucleotides to form RNA during gene expression?

RNA polymerase

-The enzyme responsible for transcription is RNA polymerase.


In eukaryotic cells, a terminator in mRNA synthesis is _____.

a specific nucleotide sequence in DNA that signals the RNA polymerase to stop


One strand of a DNA molecule has the following sequence: 3′-AGTACAAACTATCCACCGTC-5′. In order for transcription to occur in that strand, there would have to be a specific recognition sequence, called a(n) _____, to the left of the DNA sequence indicated.



During the transcription of a given portion of a DNA molecule _____.

mRNA is synthesized on only one of the chains


In transcription, _____.

-the promoter region acts as an initial binding site for RNA polymerase
-only one of the DNA strands is used as the template
-the RNA nucleotides used are produced by the cell


Which of the following statements is false?

In bacteria, proteins called transcription factors enhance the affinity of RNA polymerase to the promoter sites of genes.

-This statement is false. Transcription factors are required to initiate transcription in eukaryotes. In bacteria, the RNA polymerase alone can bind to the promoter site of a gene.


In eukaryotes, which of the following mechanisms of gene regulation operates after transcription, but before translation of mRNA into protein?

RNA splicing

-Introns are deleted and exons are spliced together after transcription and before translation.


Which of the following accurately describes the usual process of transcription for eukaryotic genes?

Exons are transcribed, but the RNA transcribed from introns does not leave the nucleus.


Which of the following statements correctly describes mRNA processing?

Introns are cut out of the primary transcript, and the resulting exons are spliced together.

-Eukaryotic mRNA molecules are processed before leaving the nucleus; introns are removed and exons joined before the mRNA enters the cytoplasm for translation.


The structures called snRNPs are _____.

part of a spliceosome

-Particles called small nuclear ribonucleoproteins, or snRNPs, recognize the splice sites and are part of a larger assembly, called a spliceosome.


Nuclei of eukaryotic cells contain spliceosomes that are made up of _____.

snRNA and protein


A cell biologist found that two different proteins with largely different structures were translated from two different mRNAs. These mRNAs, however, were transcribed from the same template within the cell nucleus. Which mechanism below could best account for this?

Exons from the same gene could be spliced in different ways to make different mRNAs.


The function of tRNA during protein synthesis is to _____.

deliver amino acids to their proper site during protein synthesis

-Each tRNA molecule is used repeatedly, picking up its designated amino acid in the cytosol, depositing this cargo at the ribosome, and leaving the ribosome to pick up another load.


Which of the following summaries of protein synthesis is correct?

Messenger RNA is made on a DNA template, and then amino-acid-bearing transfer RNAs bind to it through codon-anticodon pairing.


The bonds that hold tRNA molecules in the correct three-dimensional shape are _____.

hydrogen bonds


During translation in a eukaryotic cell _____.

polypeptides are synthesized at ribosomes, according to instructions carried by mRNA


The P site of a ribosome does which of the following?

It holds the tRNA carrying the growing polypeptide chain.


The first amino acid inserted into a new polypeptide chain in eukaryotic cells is usually _____.



Which of the following is a post-translational modification of a polypeptide?

cleavage of a polypeptide into two or more chains

-Once a polypeptide has been formed during translation, it can undergo post-translational modifications.


During translation, amino acid chain elongation occurs until _____.

the ribosome encounters a "stop" codon

-Translation stops because of a signal present within the mRNA.


Polysomes may be defined as _____.

groups of ribosomes

-Polysomes are involved in translation.


Cells are able to distinguish proteins destined for secretion or for segregation to specific intracellular compartments from those that will remain in the cytoplasm because _____.

some proteins, as they begin to be synthesized, contain a signal region that causes the ribosome with its growing polypeptide to attach to the ER and translocate the polypeptide into the lumen (space) of the ER


What is the proper order of the following events in the expression of a eukaryotic gene?

1. translation
2. RNA processing
3. transcription
4. modification of protein

3, 2, 1, 4

-In eukaryotic cells, the transcription of a pre-mRNA is followed by processing. The mRNA then moves to the cytoplasm, where ribosomes construct a polypeptide based on the codons in the RNA. The polypeptide is then modified, if necessary.


The mRNA codons 5′-CAA-3′ or 5′-CAG-3′ are translated as the amino acid glutamine by _____.

the same tRNA with the anticodon 3′-GUU-5′


Which of the following statements regarding the structure and function of tRNA is false?

Although each tRNA consists of a relatively short, single RNA strand, this single strand can achieve a three-dimensional structure by folding back upon itself and forming covalent bonds between complementary bases.


A virus infects a cell and randomly inserts many short segments of DNA containing a stop codon throughout an organism's chromosomes. This will probably cause _____.

manufactured proteins to be short and defective

-Alterations that insert stop codons cause premature termination of the polypeptides.


Ultraviolet (UV) radiation is damaging to cells because it _____.

causes mutations in the DNA


Transcription factors are found in _____.

archaea and eukaryotes


When genes are expressed, they produce _____.

-RNA molecules


What is a key difference in gene expression between eukaryotic and prokaryotic cells?

In prokaryotic cells, the mRNA transcript is immediately available as mRNA without processing.

-Neither prokaryotes nor eukaryotes assemble proteins directly from DNA.


In eukaryotic cells, transcription cannot begin until

several transcription factors hace bound to the promoter


Which of the following is true of a codon?

-it consists of three nucleotides.
-it may code for the same amino acid as another codon.
-it never codes for more than one amino acid.
-it is the basic unit of the genetic code.


Which of the following is NOT true of a codon?

it extends from one end of a tRNA molecule


The anticodon of a particular tRNA molecule is

complementary to the corresponding mRNA codon


Which of the following is true of RNA processing?

-nucleotides may be added at both ends of the RNA
-ribozymes may function in RNA splicing
-RNA splicing can be catalyzed by spliceosomes
-a primary transcript is often much longer than the final RNA molecule that leaves the nucleus


Which of the fallowing is NOT true of RNA processing?

exons are cut out before mRNA leaves the nucleus


Which component is NOT directly involved in translation?



which components are directly involved in translation?



Identify a 5' ---> 3' sequence of nucleotides in the DNA template strand for an mRNA coding for the polypeptide sequence Phe-Pro-Lys.



Which of the following mutations would be most likely to have a harmful effect on an organism?

a single nucleotide insertion downstream of, and close to, the start of the coding sequence


Messenger RNA (mRNA) Functions

carries information specifying amino acid sequences of proteins from DNA to ribosomes


Transfer RNA (tRNA) Functions

serves as translator molecule in protein synthesis; translates mRNA codons into amino acids


Ribosomal RNA (rRNA) Functions

plays catalytic (ribozyme) toles and structural roles in ribosomes


Primary transcript Functions

is a precursor to mRNA, rRNA, or tRNA, before being processed; some intron RNA acts as a ribozyme, catalyzing its own splicing


Small nuclear RNA (snRNA) Functions

plays structural and catalytic roles in spliceosomes, the complexes of protein and RNA that splice pre-mRNA