bio quiz 10 (lectures 16 and 17)

If a DNA sample were composed of 10% thymine, what would be the percentage of guanine?

40%

The figure below represents a tRNA that recognizes and binds a particular amino acid (in this instance, phenylalanine). Which codon on the mRNA strand codes for this amino acid?

5' UUC 3'

Which of the following statements is TRUE?

DNA is transcribed and RNA is translated

How do some scientists feel that telomerase might be used to slow the aging process?

If telomerase activity was increased in our cells, the rate at which our chromosomes shorten as we age might be decreased.

Which of the following statements about pre-mRNAs (primary mRNAs) is correct?

Introns are removed from primary mRNAs by splicing Primary mRNAs may contain both exons and introns PolyA tails are added to primary mRNAs Correct: all of these answers are correct

What is the function of the release factor?

It binds to the stop codon in the A site in place of a tRNA.

Which of the following statements describes the eukaryotic chromosome?

It consists of a single linear molecule of double-stranded DNA plus proteins.

Which of the following statements about the genetic code is TRUE?

Mitochondrial genes use a slightly different genetic code than nuclear genes.

What is meant by the description "antiparallel" regarding the strands that make up DNA?

The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand.

A particular triplet of bases in the coding strand of a gene is AAA. If an mRNA is made from this gene, the anticodon on the tRNA that will bind the codon on the mRNA is

UUU

A particular triplet of bases in the template strand of DNA is TTT. The anticodon on the tRNA that binds the mRNA codon is

UUU

Which of the following types of mutation, resulting in an error in the mRNA just after the AUG start of translation, is likely to have the LEAST serious effect on the polypeptide product?

a deletion of three nucleotides

A chromosome is

a single long DNA molecule plus the proteins with which that DNA molecule is complexed

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

The formation of hydrogen bonds between complementary nucleotides is known as

base pairing

In a nucleosome, the DNA is wrapped around

histones.

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

several transcription factors (TFs)

The leading and the lagging strands differ in that

the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction.

During translation, after the ribosome breaks the bond between the growing polypeptide chain and the tRNA in the P site and then forms a covalent (peptide) bond between the growing polypeptide chain and the amino acid attached to the tRNA in the A site,

the ribosome shifts over one codon on the mRNA, such that the codon specifying the next amino acid is now lined up with the A site

What is the function of DNA polymerase III?

to add nucleotides to the 3' end of a growing DNA strand

Cytosine makes up 38% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?

12

How many different amino acids could be specified if codons were two nucleotides in length?

16

How many different amino acids could be specified if codons were four nucleotides in length?

256

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 could possibly be made?

27

A possible sequence of nucleotides in the template strand of DNA that would code for the polypeptide sequence phe-leu-ile-val would be

3' AAA-GAA-TAA-CAA 5'.

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

3' CCA 5'

A part of an mRNA molecule with the following sequence is being read by a ribosome: 5' CCG-ACG 3' (mRNA). The anticodon loop of the first tRNA that will complement this mRNA is

3' GGC 5'

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'

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

3' UUA 5'

At a specific area of a chromosome, the sequence of nucleotides below is present where the chain opens to form a replication fork: 3' C C T A G G C T G C A A T C C 5' An RNA primer is formed starting at the underlined T (T) of the template. Which of the following represents the primer sequence?

5' A C G U U A G G 3'

What would be the sequence of the DNA molecule made by replication of the DNA molecule shown below? 5' AAGGCTT 3'

5' AAGCCTT 3'

The nucleotide sequence of the coding strand of a DNA molecule is shown below. What will be the nucleotide sequence of the RNA molecule made from this segment of DNA? 5' AATTCGGG 3'

5' AAUUCGGG 3'

The nucleotide sequence of the template strand of a DNA molecule is shown below. What will be the nucleotide sequence of the RNA molecule made from this segment of DNA? 5' AATTCGGG 3'

5' CCCGAAUU 3'

The nucleotide sequence of the template strand of a DNA molecule is shown below. What will be the nucleotide sequence of the RNA molecule made from this segment of DNA? 5' TTTAAGG 3'

5' CCUUAAA 3'

An Okazaki fragment has which of the following arrangements?

5' RNA nucleotides, DNA nucleotides 3'

What would be the sequence of the DNA molecule made by replication of the DNA molecule shown below? 5' GCGAATA 3'

5' TATTCGC 3'

A peptide has the sequence NH2-phe-pro-lys-gly-phe-pro-COOH. Which of the following sequences in the coding strand of the DNA would code for this peptide?

5' TTT-CCC-AAA-GGG-TTT-CCC 3'

The nucleotide sequence of the coding strand of a DNA molecule is shown below. What will be the nucleotide sequence of the RNA molecule made from this segment of DNA? 5' TTTAAGG 3'

5' UUUAAGG 3'

Which of the following statements is TRUE?

5' and 3' untranslated regions (UTRs) are parts of exons, but do not code for proteins.

The nucleotide sequence of the template strand of a DNA molecule is shown below. What will be the nucleotide sequence of the RNA molecule made from this segment of DNA? 5' ATGCGTA 3'

5'UACGCAU 3'

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 different artificial mRNA 3 nucleotide codons could possibly be made?

8

Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?

8%

In an analysis of the nucleotide composition of DNA, which of the following will be found?

A + C = G + T

A particular triplet of bases in the coding strand of a gene is TTT. If an mRNA is made from this gene, the anticodon on the tRNA that will bind the codon on the mRNA is

AAA

A particular triplet of bases in the template strand of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is

AAA

The nitrogenous base adenine is found in all members of which group?

ATP, RNA, and DNA

A space probe returns with a culture of a microorganism found on a distant planet. Analysis shows that it is a carbon-based life-form that has DNA. You grow the cells in 15N medium for several generations and then transfer them to 14N medium and grown them for another generation. Which pattern in the figure shown below would you expect if the DNA was replicated in a conservative manner?

B

Why do our chromosomes become shorter as we age?

Because DNA polymerases can only add nucleotides to an existing nucleotide chain, an RNA primer is used to initiate DNA synthesis. Once that RNA primer is removed from the end of a linear chromosome, there is no mechanism to completely fill in the missing nucleotides at the end of a linear chromosome.

A particular triplet of bases in the coding strand of a gene is GGG. If an mRNA is made from this gene, the anticodon on the tRNA that will bind the codon on the mRNA is

CCC

In the late 1950s, Meselson and Stahl grew bacteria in a medium containing "heavy" nitrogen (15N) and then transferred them to a medium containing 14N. Which of the results in the figure shown below would be expected after one round of DNA replication in the presence of 14N?

D

Which component is not directly involved in translation?

DNA

Suppose you are provided with an actively dividing culture of E. coli bacteria to which radioactive thymine has been added. What would happen if a cell replicates once in the presence of this radioactive base?

DNA in both daughter cells would be radioactive.

A biochemist isolates, purifies, and combines in a test tube a variety of molecules needed for DNA replication. When she adds some DNA to the mixture, replication occurs, but each DNA molecule consists of a normal strand paired with numerous segments of DNA a few hundred nucleotides long. What has she probably left out of the mixture?

DNA ligase

Which of the following enzymes removes the RNA nucleotides from the primer and adds equivalent DNA nucleotides to the 3' end of DNA fragments resulting from DNA replication of one of the two DNA strands?

DNA polymerase I

Which enzyme catalyzes the elongation of a DNA strand in the 5' → 3' direction?

DNA polymerase III

What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized?

DNA polymerase can join new nucleotides only to the 3' end of a growing strand.

A new DNA strand elongates only in the 5' to 3' direction because

DNA polymerase can only add nucleotides to the free 3' end.

Why are primases necessary in order for DNA replication to occur?

DNA polymerases can not initiate synthesis of new nucleotide chains

Eukaryotic telomeres replicate differently than the rest of the chromosome. This is a consequence of which of the following?

DNA polymerases can only add deoxyribonucleotides to the 3' end of an existing nucleotide chain

Which of the following statements regarding DNA polymerases is TRUE?

DNA polymerases can only add nucleotides to the 3' end of a nucleotide chain DNA polymerases can NOT initiate synthesis of a new deoxyribonucleotide chain Correct: -all of these statements are true DNA polymerases can add nucleotides to the 3' end of an RNA molecule

The process by which DNA molecules are copied so that when cells divide each cell can have a complete copy of the DNA is known as

DNA replication

Which of the following correctly shows the flow of information in a cell?

DNA to RNA to protein

E. coli cells grown on 15N medium are transferred to 14N medium and allowed to grow for two more generations (two rounds of DNA replication). DNA extracted from these cells is centrifuged. Which of the samples shown in the figure below shows the density distribution of DNA you would expect in this experiment?

E

What is meant by the statement that "the genetic code is not ambiguous"?

Each codon specifies just one amino acid.

What are the coding segments of a stretch of eukaryotic DNA called?

Exons

Which of the following statements about RNA processing is FALSE?

Exons are cut out before mRNA leaves the nucleus.

Which of the following shows the correct base pairing of deoxyribonucleotides that occurs in nature?

G with C

A particular triplet of bases in the template strand of DNA is GGG. The anticodon on the tRNA that binds the mRNA codon is

GGG

Which of the following statements about histones is FALSE?

Histones help transport mRNA molecules out of the nucleus

Will the chromosomes you pass onto your children be shorter than your chromosomes?

Hopefully not, because telomerase will restore the telomeres in your germline cells (the cells that produce egg or sperm cells) to approximately their original length.

The "universal" genetic code is now known to have exceptions. Evidence for this can be found if which of the following is true?

If UGA, usually a stop codon, is found to code for an amino acid such as tryptophan (usually coded for by UGG only).

What happens to the short RNA "primers" that primase synthesizes and that are extended by DNA polymerase III during DNA replication?

In E. coli, DNA polymerase I removes the RNA primers and fills in the resulting gaps with deoxyribonucleotides

Which of the following statements about a codon is FALSE?

It extends from one end of a tRNA molecule.

What is the role of DNA ligase during DNA replication?

It joins DNA fragments together.

What is meant by the statement that "the genetic code is redundant"?

Most amino acids are specified by more than one codon.

Why are there concerns about using increased telomerase activity to slow down the aging process?

One concern is that increasing telomerase activity could increase cancer rates.

Which of the following statements regarding primases is TRUE?

Primases can initiate synthesis of a new nucleotide chain Primases catalyze the formation of an RNA molecule Correct Answer: all of these statements are true Primases add nucleotides to the 3' end of a nucleotide or nucleotide chain

Which of the following is NOT a major difference between transcription in prokaryotes versus eukaryotes?

Prokaryotic mRNA molecules are synthesized by RNA polymerase catalyzing the formation of phosphodiester bonds between ribonucleotides that are base paired with the DNA template strand; eukaryotic mRNA molecules are synthesized by RNA polymerase catalyzing the formation of phosphodiester bonds between ribonucleotides that are base paired with the DNA coding strand

Which of the following shows the correct base pairing of deoxyribonucleotides that occurs in nature?

T with A

Why do some scientists feel that telomerase might be used to slow the aging process?

Telomere extension in mice and worms has reversed some signs of aging.

What is "chromatin"?

The combination of DNA and proteins that forms chromosomes

In comparing DNA replication with transcription, which of the following is true only of DNA replication?

The entire template molecule is represented in the product.

When the genome of a particular species is said to include 20,000 protein-coding regions, what does this imply?

There are also genes for RNAs other than mRNA.

Which of the following statements is true about protein synthesis in prokaryotes?

Translation can begin while transcription is still in progress.

Which of the following shows the correct base pairing of ribonucleotides that occurs in nature?

U with A

Which of the following will happen to your chromosomes as you become older?

Your chromosomes will become shorter.

Which of the following types of mutation, resulting in an error in the mRNA just after the AUG start of translation, is likely to have the MOST serious effect on the polypeptide product?

a deletion of two nucleotides

Which of the following would you expect of a eukaryote lacking telomerase?

a reduction in chromosome length in gametes

When a ribosome reaches the end of the coding region of an mRNA molecule, so that a stop codon is in the A site of the ribosome,

a release factor binds the stop codon at the A site and the polypeptide is freed from the tRNA in the P site

If an organism uses the "conservative" model of DNA replication, rather than the normal "semi-conservative" model of DNA replication,

after DNA replication occurs, one of the two double-stranded DNA molecules will consist of two "daughter" DNA strands and the other will consist of two "parental" DNA strands

The enzyme that catalyzes the formation of a covalent bond between a tRNA and a specific amino acid is

an aminoacyl tRNA synthetase

Transfer RNAs, or tRNAs

are translated to form short polypeptides that are part of ribosomes. Correct Answer: -None of these answers is correct. form 3-dimensional shapes as a result of ionic bonds between different parts of the molecule. are important components of ribosomes

Transfer RNAs, or tRNAs

bind only a specific amino acid Correct Answer: -All of these answers are correct. contain an anticodon that base pairs with an appropriate codon on a mRNA molecule have 3-dimensional shapes that are formed by hydrogen bonding between the nitrogenous bases of some of the ribonucleotides comprising the tRNA

During translation, the role of release factors is to

bind the mRNA stop codon in the A site of the ribosome, causing release of the completed polypeptide

Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the

bonding of the anticodon to the codon and the attachment of amino acids to tRNAs.

Aminoacyl tRNA synthetases

catalyze the formation of a covalent bond between an amino acid and an appropriate tRNA molecule

Which of the following statements is TRUE?

coding regions are part of exons 3' UTRs are part of exons Correct Answer: -all of these answers are correct 5' UTRs are part of exons

The group of three nucleotides that specifies an amino acid is known as a

codon

The pairs of nucleotides that interact to join together two DNA strands are known as

complementary nucleotides

The anticodon of a particular tRNA molecule is

complementary to the corresponding mRNA codon.

The "polyA" tail that is added to the 3' end of eukaryotic mRNA molecules

consists of a string of adenosine ribonucleotides

The reaction used to join together nucleotides to form a nucleotide chain is known as a

dehydration reaction

The elongation of the leading strand during DNA synthesis

depends on the action of DNA polymerase.

According to the "semi-conservative" model of DNA replication, after a double-stranded DNA molecule is replicated

each of the two resulting double-stranded DNA molecules will consist of one "daughter" and one "parental" DNA strand

Which of the following types of RNA molecules have polyA tails?

eukaryotic mRNA molecules

What type of bonding is responsible for maintaining the shape of a tRNA molecule?

hydrogen bonding between base pairs

The two strands of a double-stranded DNA molecule are held together by

hydrogen bonds

The two strands of a double-stranded DNA molecule are held together by

hydrogen bonds between complementary nitrogenous bases

A single aminoacyl tRNA synthetase can typically recognize

just one amino acid, but several tRNAs

You briefly expose bacteria undergoing DNA replication to radioactively labeled nucleotides. When you centrifuge the DNA isolated from the bacteria, the DNA separates into two classes. One class of labeled DNA includes very large molecules (thousands or even millions of nucleotides long), and the other includes short stretches of DNA (several hundred to a few thousand nucleotides in length). These two classes of DNA probably represent

leading strands and Okazaki fragments.

Which of the following enzymes covalently connects segments of DNA?

ligase

Which of the following statements about translation is TRUE?

mRNA molecules are read by the translation machinery in the 5' to 3' direction. Translation of an mRNA begins at an AUG codon The 5' and 3' UTRs of an mRNA molecule are not translated. Correct: -All of these statements are true.

A transcription unit that is 8,000 nucleotides long may use 1,200 nucleotides to make a protein consisting of approximately 400 amino acids. This is best explained by the fact that

many noncoding stretches of nucleotides are present in mRNA.

What amino acid sequence will be generated, based on the following mRNA codon sequence? 5' AUG-UCU-UCG-UUA-UCC-UUG 3'

met-ser-ser-leu-ser-leu

Which of the following represents the order of increasingly higher levels of organization of chromatin?

nucleosome, 30-nm chromatin fiber, looped domain

DNA polymerases can add deoxyribonucleotides to

only the 3' end of an existing nucleotide chain

DNA replication begins are special sites on the parental DNA molecule known as

origins of replication

The covalent linkages joining together nucleotides in a DNA molecule are known as

phosphodiester linkages

Which of the following is NOT a typical modification of a eukaryotic primary (or precursor) mRNA?

phosphorylation

Which of the following enzymes initiates the synthesis of a new nucleotide chain during DNA replication?

primase

Which of the following enzymes synthesizes short segments of RNA?

primase

A part of an mRNA molecule with the following sequence is being read by a ribosome: 5' CCG-ACG 3' (mRNA). The charged transfer RNA molecules (with their anticodons shown in the 3' to 5' direction) shown in the table below are available. Two of them can correctly match the mRNA so that a dipeptide can form. The dipeptide that will form will be

proline-threonine.

Histones are

proteins around which the DNA in chromosomes wrap

When a DNA molecule is replicated,

replication generally occurs by a "semi-conservative" mechanism Correct Answer: -all of these answers are correct the DNA strands that are made by copying the parental DNA strands are known as the "daughter" strands the DNA strands in the original molecule are known as the "parental" DNA strands

Which of the following describes the sequence of events that occurs during DNA replication of a double-stranded DNA molecule?

separation of the DNA strands at DNA replication origins, unwinding of the DNA double helix, synthesis of RNA primers, synthesis of DNA, ligation of DNA fragments

The DNA molecule is able to carry a vast amount of hereditary information in which of the following?

sequence of bases

In eukaryotic cells, transcription cannot begin until

several transcription factors have bound to the promoter.

The DNA strand to which ribonucleotides hydrogen bond during transcription is known as the

template strand

During translation, tRNAs leave the ribosome from

the E site

Telomeres are

the ends of linear chromosomes

Scientists sometimes transfer genes from one species to a different species. What property of the genetic code typically allows these genes to produce a protein of the same amino acid sequence in the new species as they did in the original species?

the genetic code is almost universal

During translation,

the growing polypeptide chain is transferred from the tRNA in the P ribosome site to the amino acid attached to the tRNA in the A ribosome site.

The difference between ATP and the nucleoside triphosphates used during DNA synthesis is that

the nucleoside triphosphates have the sugar deoxyribose; ATP has the sugar ribose.

How do the nucleotides used to make RNA molecules differ from those used to make DNA molecules?

the nucleotides used to make RNA molecules have ribose instead of deoxyribose as their sugar and uracil instead of thymine as one of their nitrogenous bases

During translation, after the ribosome breaks the bond between the growing polypeptide chain and the tRNA in the P site and then forms a covalent (peptide) bond between the growing polypeptide chain and the amino acid attached to the tRNA in the A site,

the position of the ribosome on the mRNA shifts and a new, charged tRNA enters the A site of the ribosome

During translation, after the ribosome breaks the bond between the growing polypeptide chain and the tRNA in the P site and then forms a covalent (peptide) bond between the growing polypeptide chain and the amino acid attached to the tRNA in the A site,

the tRNA that was in the P site is now in the E site and leaves the ribosome

For the DNA molecule shown below, where would the promoter be located?

to the right of the template strand

Which of the following are needed for the initiation of transcription?

transcription factors Correct: -all of these answers are correct a promoter sequence RNA polymerase

Which of the following help form a transcription complex at a promoter?

transcription factors and RNA polymerase