Chapter 14 APBIO

Generally speaking, how many genetic codes are there?

1

The figure shows the simple metabolic pathway. Enzyme 1 catalyzes the transformation of A into B and enzyme 2 catalyzes the transformation of B into C. Examine the simple metabolic pathway in the figure. According to Beadle and Tatum's hypothesis, how many genes are necessary for this pathway?

2

The enzyme polynucleotide phosphorylase randomly assembles nucleotides into a polynucleotide polymer. You add polynucleotide phosphorylase to a solution of ATP, GTP, and UTP. How many artificial mRNA 3 nucleotide codons would be possible?

27

A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is

3' UCA 5'.

DNA template strand 5'___________________________3' DNA complementary strand 3'___________________________5' Given the locally unwound double strand in the figure, in which direction does the RNA polymerase move

3' → 5' along the template strand

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

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

3....codon

The enzyme polynucleotide phosphorylase randomly assembles nucleotides into a polynucleotide polymer. You add polynucleotide phosphorylase to a solution of adenosine triphosphate and guanosine triphosphate. How many artificial mRNA 3 nucleotide codons would be possible?

8

Which of the following does not occur in prokaryotic gene expression, but does occur in eukaryotic gene expression?

A poly-A tail is added to the 3' end of an mRNA and a cap is added to the 5' end

Which of the following statements about ribozymes is/are correct?

A ribosome can be regarded as one large ribozyme. In some genes, intron RNA functions as a ribozyme and catalyzes its own excision. Ribozymes are RNA molecules that function as enzymes.

Which of the following molecules is/are produced by translation? Include molecules that are subject to further modification after initial synthesis.

Aminoacyl-tRNA synthetase RNA polymerase

A part of the promoter, called the TATA box, is said to be highly conserved in evolution. Which of the following might this illustrate?

Any mutation in the sequence is selected against.

Which component is NOT directly involved in translation?

DNA

Which of the following mutations would likely be most dangerous to a cell?

Deletion of one nucleotide

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

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

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.

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

GCA

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.

Which of the following statements correctly describes mRNA processing?

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

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

It holds the tRNA carrying the growing polypeptide chain

Which of the following best describes the significance of the TATA box in eukaryotic promoters?

It is the recognition site for a specific transcription factor.

RNA polymerase in a prokaryote is composed of several subunits. Most of these subunits are the same for the transcription of any gene, but one, known as sigma, varies considerably. Which of the following is the most probable advantage for the organism in having such variability in RNA polymerase?

It might allow the polymerase to recognize different promoters under certain environmental conditions.

Where does RNA polymerase begin transcribing a gene into mRNA?

It starts after a certain nucleotide sequence called a promoter.

What is the function of RNA polymerase?

It unwinds the double helix and adds nucleotides to a growing strand of RNA.

Garrod's information about the enzyme alteration resulting in alkaptonuria led to further understanding of these types of metabolic pathways in humans. Phenylketonuria (PKU) occurs when another enzyme in the pathway is altered or missing, resulting in a failure of phenylalanine (phe) to be metabolized to another amino acid: tyrosine. Tyrosine is an earlier substrate in the pathway altered in alkaptonuria. How might PKU affect the presence or absence of alkaptonuria?

It would have no effect because tyrosine is also available from the diet.

The average length of a transcription unit along a eukaryotic DNA molecule is about 27,000 nucleotide pairs, whereas an averaged-sized protein is about 400 amino acids long. What is the best explanation for this fact?

Most eukaryotic genes and their RNA transcripts have long noncoding stretches of nucleotides that are not translated.

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

RNA

When genes are expressed, they produce _________

RNA molecules and polypeptides

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

RNA polymerase

In eukaryotes there are several different types of RNA polymerase. Which type is involved in transcription of mRNA known as pre-mRNA?

RNA polymerase II

Which of the following statements best describes the termination of transcription in prokaryotes?

RNA polymerase transcribes through the terminator sequence, causing the polymerase to separate from the DNA and release the transcript.

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

RNA splicing

Which of the following molecules are produced by transcription?

Ribozymes Messenger RNA

Which of the following summaries of protein synthesis is correct?

The mRNA is made on a DNA template, and then amino-acid-bearing tRNA's bind to it through codon-anticodon pairing.

The template strand of a gene contains this sequence: 3'-TAC TAG GCT AGT TGA-5'. A mutation occurs that changes the gene sequence to 3'-TAC TAG ACT AGT TGA-5'. How does this mutation affect the resulting amino acid sequence?

The mutation introduces a stop codon.

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 non-overlapping series on the DNA template strand.

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

U.....A

In order for a eukaryotic gene to be engineered into a bacterial colony to be expressed, what must be included in addition to the coding exons of the gene?

a bacterial promoter sequence

A geneticist found that a particular mutation had no effect on the polypeptide encoded by the gene. This mutation probably involved __________.

a silent or neutral mutation

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

Which of the following descriptions of nucleotide triplets best represents a codon?

a triplet in the same reading frame as an upstream AUG

The figure shows the simple metabolic pathway. Enzyme 1 catalyzes the transformation of A into B and enzyme 2 catalyzes the transformation of B into C. Examine the simple metabolic pathway in the figure. A mutation results in a defective enzyme 1. Which of the following results would be a consequence of that mutation?

an accumulation of A and no production of B and C

Transcription factors are found in __________.

archaea and eukaryotes

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

at least 1350

Who formulated the one gene-one enzyme hypothesis?

beadle and tatum

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

causes mutations in the DNA

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

cleavage of a polypeptide into two or more chains

The function of tRNA during protein synthesis is to __________.

deliver amino acids to their proper site

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

A point mutation in which a single base pair is inserted or deleted from DNA is called a(n) __________.

frame-shift mutation

The flow of information in a cell proceeds in what sequence?

from DNA to RNA to protein

Garrod hypothesized that inherited diseases such as alkaptonuria, the inability to metabolize the chemical alkapton, occur because

genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes.

Polysomes may be defined as __________.

groups of ribosomes

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

hydrogen bonds

In a eukaryotic cell, transcription takes place __________.

in the nucleus

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

mRNA is synthesized on only one of the chains

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

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

methionine

The figure shows the simple metabolic pathway. Enzyme 1 catalyzes the transformation of A into B and enzyme 2 catalyzes the transformation of B into C. Examine the simple metabolic pathway in the figure. If A, B, and C are all required for growth, a strain mutant for the gene-encoding enzyme 2 would be capable of growing on which of the following media?

minimal medium supplemented with C only

The figure shows the simple metabolic pathway. Enzyme 1 catalyzes the transformation of A into B and enzyme 2 catalyzes the transformation of B into C. Examine the simple metabolic pathway in the figure. If A, B, and C are all required for growth, a strain that is mutant for the gene-encoding enzyme 1 would be able to grow on which of the following media?

minimal medium supplemented with nutrient B only

A base-pair substitution mutation in a germ cell line is likely to have NO effect on phenotype if the substitution __________.

occurs in an intron

During translation in a eukaryotic cell __________.

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

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?

pro-lys-phe-gly

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.

promoter

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

redundant

Transcription in eukaryotes requires which of the following in addition to RNA polymerase?

several transcription factors

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

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

the genetic code is nearly universal

In transcription, __________.

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

During translation, amino acid chain elongation occurs until __________.

the ribosome encounters a "stop" codon

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'

codon consists of __________ bases and specifies which __________ will be inserted into the polypeptide chain.

three ... amino acid

DNA template strand 5'___________________________3' DNA complementary strand 3'___________________________5' In the transcription event of the DNA in the figure, where would the promoter be located?

to the right of the template strand