SQ Topic 16 BIOL1009

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? -38 -24 -12 -31

-12

If a DNA sample were composed of 10% thymine, what would be the percentage of guanine? -40% -90% -10% -80%

-40%

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' G C C T A G G 3' -5' A C G T T A G G 3' -3' G C C T A G G 5' -5' A C G U U A G G 3'

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

Which enzyme catalyzes the elongation of a DNA strand in the 5' → 3' direction? -primase -topoisomerase -DNA ligase -DNA polymerase III

-DNA polymerase III

What kind of chemical bond is found between paired bases of the DNA double helix? -Hydrogen -Phosphate -Ionic -Covalent

-Hydrogen

What is "chromatin"? -Origins of DNA replication -Special proteins that function as chromosomal attachment sites for the mitotic spindle apparatus. -The combination of DNA and proteins that forms chromosomes -The ends of linear chromosomes

-The combination of DNA and proteins that forms chromosomes

Which of the following are NOT components of a nucleotide? -a nitrogenous base -an "R" group -a phosphate group -a sugar

-an "R" group

The elongation of the leading strand during DNA synthesis: -progresses away from the replication fork. -occurs in the 3' → 5' direction. -depends on the action of DNA polymerase. -produces Okazaki fragments.

-depends on the action of DNA polymerase.

In a nucleosome, the DNA is wrapped around: -ribosomes. -satellite DNA. -histones. -polymerase molecules.

-histones.

In a double-stranded DNA molecule, the two DNA strands base pair in such a way that the 5' end of one DNA strand base pairs with the 3' end of the other DNA strand. The two DNA strands are said to be: -homologously paired -covalently bound -in an antiparallel arrangement -in an Okazaki arrangement

-in an antiparallel arrangement

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: -Okazaki fragments and RNA primers. -leading strands and Okazaki fragments. -lagging strands and Okazaki fragments. -leading strands and RNA primers.

-leading strands and Okazaki fragments.

The DNA molecule is able to carry a vast amount of hereditary information in which of the following? -phosphate-sugar backbones -sequence of bases -complementary pairing of bases -side groups of nitrogenous bases

-sequence of bases

The ends of linear chromosomes are known as: -centromeres -telomeres -DNA replication origins -endomeres

-telomeres

What is the function of DNA polymerase III? -to add nucleotides to the 3' end of a growing DNA strand -to seal together the broken ends of DNA strands -to rejoin the two DNA strands (one new and one old) after replication -to unwind the DNA helix during replication

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

What would be the sequence of the DNA molecule made by replication of the DNA molecule shown below?5' AAGGCTT 3' -5' TTCGGAA 3' -5' AAGCCUU 3' -5' TTCCGAA 3' -5' AAGCCTT 3'

-5' AAGCCTT 3'

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

-5' TATTCGC 3'

What would be the sequence of the DNA molecule made by replication of the DNA molecule shown below?5' TTCCGGA 3' -5' UCCGGAA 3' -5' TCCGGAA 3' -5' AAGGCCT 3' -5' AAGGCCT 3'

-5' TCCGGAA 3'

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? -58% -16% -8% -42%

-8%

In an analysis of the nucleotide composition of DNA, which of the following will be found? -A + C = G + T -A = G and C = T -G + C = T + A -A = C

-A + C = G + T

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 -E -D -C

-B

Why do our chromosomes become shorter as we age? -Because DNA repair enzymes become defective as we age. -All of these answers are correct. -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. -Because DNA polymerase becomes defective as we age, so that it is not able to fully replicate our DNA within a single replication cycle.

-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.

Which of the following shows the correct base pairing of deoxyribonucleotides that occurs in nature? -C with T -C with A -C with U -C with G

-C with G

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? -C -D -B -E

-D

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. -Neither of the two daughter cells would be radioactive. -All four bases of the DNA would be radioactive. -One of the daughter cells, but not the other, would have radioactive DNA.

-DNA in both daughter cells would be radioactive.

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 III -helicase -DNA polymerase I -primase

-DNA polymerase I

What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized? -Polymerase can work on only one strand at a time. -DNA ligase works only in the 3' → 5' direction. -The origins of replication occur only at the 5' end. -DNA polymerase can join new nucleotides only to the 3' end of a growing strand.

-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 begins adding nucleotides at the 5' end of the template. -DNA polymerase can only add nucleotides to the free 3' end. -replication must progress toward the replication fork. -the polarity of the DNA molecule prevents addition of nucleotides at the 3' end.

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

Why are primases necessary in order for DNA replication to occur? -Primases modify DNA molecules to allow replication of those molecules by DNA polymerases -Primases modify deoxyribonucleotides to allow them to serve as substrates for DNA polymerases -Primases modify DNA polymerases to allow them to carry out their function. -DNA polymerases can not initiate synthesis of new nucleotide chains

-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 5' end of an existing nucleotide chain -the evolution of telomerase enzyme -DNA polymerases can only add deoxyribonucleotides to the 3' end of an existing nucleotide chain -the "no ends" of a circular chromosome

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

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: -chromosome duplication -DNA transcription -DNA ligation -DNA replication

-DNA replication

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? -D -C -E -B

-E

Which of the following statements about histones is FALSE? -Histones help package DNA -Histones help transport mRNA molecules out of the nucleus -Histones are an important component of chromatin -Histones are composed of amino acids

-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. -Yes, because DNA repair enzymes do not function properly in germline cells (the cells that produce egg or sperm cells). -Yes, because DNA polymerase is not able to fully replicate the ends of chromosomes. -No, because DNA repair enzymes will fill in any missing gaps at the ends of 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.

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 -DNA ligases join the RNA primers to DNA fragments to create a single, long nucleotide chain -DNA repair enzymes chemically modify the ribonucleotides so that they are converted to deoxyribonucleotides -The RNA primers are unwound by helicases.

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

Which of the following statements describes the eukaryotic chromosome? -The number of genes on each chromosome is different in different cell types of an organism. -The structure of the chromosome is determined by the nucleotide sequence of its DNA. -It is composed of DNA alone. -It consists of a single linear molecule of double-stranded DNA plus proteins.

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

What is the role of DNA ligase during DNA replication? -It unwinds the parental double helix. -It joins DNA fragments together. -It synthesizes RNA nucleotides to make a primer. -It catalyzes the lengthening of telomeres.

-It joins DNA fragments together.

Why are there concerns about using increased telomerase activity to slow down the aging process? -All of these answers are correct. -One concern is that increasing telomerase activity could increase joint problems. -One concern is that increasing telomerase activity could increase cancer rates. -One concern is that increasing telomerase activity could increase diabetes rates.

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

Which of the following shows the correct base pairing of deoxyribonucleotides that occurs in nature? -T with C -T with U -T with A -T with G

-T with A

Why do some scientists feel that telomerase might be used to slow the aging process? -There is no real evidence; the idea that telomerase could be used to help reduce aging is based solely on theoretical arguments. -Telomere extension in mice and worms allowed them to live to be approximately 100 years old -Teleomere extension in humans has reversed some signs of aging. -Telomere extension in mice and worms has reversed some signs of aging.

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

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. -One strand is positively charged and the other is negatively charged. -The twisting nature of DNA creates nonparallel strands. -One strand contains only purines and the other contains only pyrimidines.

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

The order in which chromatin packing occurs is as follows: -The DNA wraps around histones, forming nucleosomes; the chromatin forms loops by attaching to scaffold proteins; the histones within each nucleosome interact with adjacent nucleosomes and with the DNA between nucleosomes to form a 30-nm fiber -The histones within nucleosomes interact with adjacent nucleosomes and with the DNA between nucleosomes to form a 30-nm fiber; the chromatin forms loops by attaching to scaffold proteins, forming a 300-nm fiber; the DNA wraps around histones, forming nucleosomes -The chromatin forms loops by attaching to scaffold proteins; the histones within nucleosomes interact with adjacent nucleosomes and with the DNA between nucleosomes to form a 30-nm fiber; the DNA wraps around histones, forming nucleosomes -The DNA wraps around histones, forming nucleosomes; the histones within each nucleosome interact with adjacent nucleosomes and with the DNA between nucleosomes to form a 30-nm fiber; the chromatin forms loops by attaching to scaffold proteins, forming a 300-nm fiber

-The DNA wraps around histones, forming nucleosomes; the histones within each nucleosome interact with adjacent nucleosomes and with the DNA between nucleosomes to form a 30-nm fiber; the chromatin forms loops by attaching to scaffold proteins, forming a 300-nm fiber

In an experiment, DNA is allowed to replicate in an environment with all necessary enzymes, dATP, dCTP, dGTP, and radioactively labeled dTTP (3H thymidine) for several minutes and then switched to nonradioactive medium. It is then viewed by electron microscopy and autoradiography. The figure shown below represents the results.The grains in the figure represent radioactive material within the replicating eye.Which of the following is the most likely interpretation? -Thymidine is only being added where the DNA strands are furthest apart. -Replication proceeds in one direction only. -Thymidine is only added at the very beginning of replication. -There are two replication forks going in opposite directions.

-There are two replication forks going in opposite directions.

Which of the following will happen to your chromosomes as you become older? -Your chromosomes will become shorter. -The frequency of mutations will become smaller as DNA repair enzymes do their job. -Your DNA will accumulate segments of RNA that are left over from the work of primase. -All of these answers are correct.

-Your chromosomes will become shorter.

Which of the following would you expect of a eukaryote lacking telomerase? -a high probability of somatic cells becoming cancerous -increased rates of DNA mutations -inability to repair thymine dimers -a reduction in chromosome length in gametes

-a reduction in chromosome length in gametes

A chromosome is: -a single long DNA molecule plus the short RNA molecules with which that DNA molecule is complexed -the group of proteins that bind to DNA molecules -a single long DNA molecule plus the proteins with which that DNA molecule is complexed -a single long DNA molecule

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

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

-all of these answers are correct

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

-all of these statements are true

Which of the following statements regarding primases is TRUE? -all of these statements are true -Primases catalyze the formation of an RNA molecule -Primases can initiate synthesis of a new nucleotide chain -Primases add nucleotides to the 3' end of a nucleotide or nucleotide chain

-all of these statements are true

The formation of hydrogen bonds between complementary nucleotides is known as: -complementation -base pairing -homologous joining -DNA binding

-base pairing

The pairs of nucleotides that interact to join together two DNA strands are known as: -partner nucleotides -homologous nucleotides -complementary nucleotides -homozygous nucleotides

-complementary nucleotides

The reaction used to join together nucleotides to form a nucleotide chain is known as a: -dehydration reaction -DNA catalysis reaction -phosphodiesterase reaction -hydrolysis reaction

-dehydration reaction

According to the "semi-conservative" model of DNA replication, after a double-stranded DNA molecule is replicated: -one of the two resulting double-stranded DNA molecules will consist of two "daughter" DNA strands and the other double-stranded DNA molecule will consist of two "parental" DNA strands -each of the two resulting double-stranded DNA molecules will consist of one "daughter" and one "parental" DNA strand -each DNA strand of one of the two resulting double-stranded DNA molecules will consist partly of "daughter" DNA and partly of "parental" DNA and each DNA strand of the other double-stranded DNA molecule will consist solely of "daughter" DNA -each DNA strand of each of the two resulting double-stranded DNA molecules will consist partly of "daughter" DNA and partly of "parental" DNA

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

The two strands of a double-stranded DNA molecule are held together by: -polar covalent bonds -nonpolar covalent bonds -ionic bonds -hydrogen bonds

-hydrogen bonds

The two strands of a double-stranded DNA molecule are held together by: -ionic bonds between phosphate groups and nitrogenous bases -hydrogen bonds between sugar groups -hydrogen bonds between phosphate groups -hydrogen bonds between complementary nitrogenous bases

-hydrogen bonds between complementary nitrogenous bases

Which of the following enzymes covalently connects segments of DNA? -DNA polymerase I -DNA polymerase III -ligase -primase

-ligase

Which of the following represents the order of increasingly higher levels of organization of chromatin? -nucleosome, 30-nm chromatin fiber, looped domain -30-nm chromatin fiber, nucleosome, looped domain -looped domain, 30-nm chromatin fiber, nucleosome -nucleosome, looped domain, 30-nm chromatin fiber

-nucleosome, 30-nm chromatin fiber, looped domain

DNA polymerases can add deoxyribonucleotides to: -only the 3' end of an existing nucleotide chain -either the 3' or the 5' end of an existing nucleotide chain -only the end of an RNA chain -only the 5' end of an existing nucleotide chain

-only the 3' end of an existing nucleotide chain

DNA replication begins are special sites on the parental DNA molecule known as: -Okazaki regions -primase binding sites -DNA polymerase binding sites -origins of replication

-origins of replication

Histones are: -part of nucleosomes -part of DNA replication origins -part of centromeres -part of telomeres

-part of nucleosomes

Which of the following enzymes initiates the synthesis of a new nucleotide chain during DNA replication? -primase -DNA polymerase II -DNA polymerase III -DNA polymerase I

-primase

Which of the following enzymes synthesizes short segments of RNA? -DNA polymerase I -primase -DNA polymerase III -ligase

-primase

Histones are: -proteins around which the DNA in chromosomes wrap -proteins that bind solely to centromeres -proteins that bind solely to telomeres -proteins that help unwind DNA prior to DNA replication

-proteins around which the DNA in chromosomes wrap

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

-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

Telomeres are: attachment sites for the mitotic spindle apparatus -part of the extracellular matrix -pores in the nuclear membrane that allow for passage of materials --into and out of the nucleus -the ends of linear chromosomes

-the ends of linear chromosomes

The leading and the lagging strands differ in that: -the lagging strand is synthesized continuously, whereas the leading strand is synthesized in short fragments that are ultimately stitched together. -the leading strand is synthesized by adding nucleotides to the 3' end of the growing strand, and the lagging strand is synthesized by adding nucleotides to the 5' end. -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. -the leading strand is synthesized at twice the rate of the lagging strand.

-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.

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. -the lagging strand is synthesized continuously, whereas the leading strand is synthesized in short fragments that are ultimately stitched together. -the leading strand is synthesized at twice the rate of the lagging strand. -the leading strand is synthesized by adding nucleotides to the 3' end of the growing strand, and the lagging strand is synthesized by adding nucleotides to the 5' end.

-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.

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. -triphosphate monomers are active in the nucleoside triphosphates, but not in ATP. -the nucleoside triphosphates have two phosphate groups; ATP has three phosphate groups. -ATP contains three high-energy bonds; the nucleoside triphosphates have two.

-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 -the nucleotides used to make RNA molecules have ribose instead of deoxyribose as their sugar and two phosphate groups instead of three -the nucleotides used to make RNA molecules have ribose instead of deoxyribose as their sugar and uracil instead of adenine as one of their nitrogenous bases -the nucleotides used to make RNA molecules have deoxyribose instead of ribose as their sugar and uracil instead of thymine as one of their nitrogenous bases

-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