Lecture 11 - Inheritance

Remember that C and G base pair and that A and T base pair. So, if the DNA sample is 10% thymine, it must also be 10% adenine, because base pairing of thymine and adenine requires that they be present in equal concentration. That means that 80% (100% - 10% - 10%) of the DNA sample must consist of G and C. Because G and C base pair with each other, they need to be present in equal amounts. So, the DNA sample must have 40% guanine and 40% cytosine. The correct answer is: 40%

If a DNA sample were composed of 10% thymine, what would be the percentage of guanine? Select one: a. 40% b. 90% c. 80% d. 10%

Remember that C and G base pair and that A and T base pair. So, the concentrations of C and G must be equal to each other and the concentrations of A and T must be equal to each other. If A = T and C = G, than A + C must equal G + T. The correct answer is: A + C = G + T

In an analysis of the nucleotide composition of DNA, which of the following will be found? Select one: a. A = G and C = T b. A = C c. G + C = T + A d. A + C = G + T

The correct answer is: phosphodiester linkages

The covalent linkages joining together nucleotides in a DNA molecule are known as Select one: a. peptide bonds b. phosphodiester linkages c. nucleotide linkages d. glycosidic bonds

The correct answer is: The combination of DNA and proteins that forms chromosomes

What is "chromatin"? Select one: a. The combination of DNA and proteins that forms chromosomes b. Origins of DNA replication c. Special proteins that function as chromosomal attachment sites for the mitotic spindle apparatus. d. The ends of linear chromosomes

The correct answer is: all of these answers are correct

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

"Chromatin" the mixture of DNA and proteins that forms a chromosome. The first order structure of chromatin is a "nucleosome". A nucleosome consists of double-stranded DNA wrapped around a group of proteins known as "histones". Nucleosomes than associated to form a more compact structure, known as a 30-nm fiber. Loops form in the 30-nm fiber to create an even more dense structure. The correct answer is: nucleosome, 30-nm chromatin fiber, looped domain

Which of the following represents the order of increasingly higher levels of organization of chromatin? Select one: a. nucleosome, 30-nm chromatin fiber, looped domain b. 30-nm chromatin fiber, nucleosome, looped domain c. looped domain, 30-nm chromatin fiber, nucleosome d. nucleosome, looped domain, 30-nm chromatin fiber

The correct answer is: DNA polymerase can only add nucleotides to the free 3' end.

A new DNA strand elongates only in the 5' to 3' direction because Select one: a. the polarity of the DNA molecule prevents addition of nucleotides at the 3' end. b. DNA polymerase can only add nucleotides to the free 3' end. c. replication must progress toward the replication fork. d. DNA polymerase begins adding nucleotides at the 5' end of the template.

Primase catalyzes the synthesis of short RNA "primers". DNA polymerase III than catalyzes the extension of those primers, adding deoxyribonucleotides to the 3' end of the RNA primer and forming DNA in the 5' to 3' direction. In E. coli, DNA polymerase I removes the RNA primers and fills in the resulting gaps. DNA ligase catalyzes the formation of covalent bonds between the ends of adjacent DNA fragments (i.e. Okazaki fragments), resulting in formation of a single, long DNA molecule. The correct answer is: ligase

Which of the following enzymes covalently connects segments of DNA? Select one: a. primase b. ligase c. DNA polymerase I d. DNA polymerase III

One concern is that trying to keep telomeres longer could cause increased rates of cancer. Telomerase is more active in ~ 90% of tumor cells. However, the link between telomere length and cancer is currently VERY unclear. There is no evidence linking telomere length with diabetes or joint problems. The correct answer is: One concern is that increasing telomerase activity could increase cancer rates.

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

The numerous segments of DNA a few hundred nucleotides long likely correspond to Okazaki fragments, formed during synthesis of the lagging strand. DNA ligase is needed to form covalent bonds between the ends of adjacent Okazaki fragments. The correct answer is: DNA ligase

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? Select one: a. DNA ligase b. DNA polymerase c. primase d. Okazaki fragments

The correct answer is: a single long DNA molecule plus the proteins with which that DNA molecule is complexed

A chromosome is Select one: a. a single long DNA molecule plus the proteins with which that DNA molecule is complexed b. a single long DNA molecule plus the short RNA molecules with which that DNA molecule is complexed c. a single long DNA molecule d. the group of proteins that bind to DNA molecules

DNA replication by a conservative, rather than the normal semi-conservative, model would mean that replication of a double-stranded DNA molecule would result in formation of two double-stranded DNA molecules, one of which would consist of two "parental" (i.e. original) DNA strands and the other of which would consist of two "daughter" (i.e. new) DNA strands. So, in the example shown above, the double-stranded DNA molecule that would consist of two parental DNA strands would have a weight equal to the weight of DNA synthesized entirely using 15N. In contast, the double-stranded DNA molecule that would consist of two daughter DNA strands would have a weight equal to the weight of DNA synthesized entirely using 14N. The correct answer is: B

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? Select one: a. E b. B c. C d. D

Okazaki fragments are the short DNA fragments that are made as the lagging DNA strand is synthesized. Remember that nucleotide chains are always synthesized in the 5' to 3' direction and that DNA polymerases only add nucleotides to the end of an existing nucleotide chain. So, DNA synthesis is initiated by an enzyme called primase, which catalyzes the formation of a short RNA primer, using the DNA molecule being copied as a template. DNA polymerase III then catalyzes the addition of deoxyribonucleotides to the 3' end of the RNA primer. So, the short nucleotide chains that are formed during synthesis of the lagging strand (and the long nucleotide chain that is formed during synthesis of the leading strand) consists of RNA nucleotides (ribonucleotides) at the 5' end and DNA nucleotides (deoxyribonucleotides) at the 3' end. The correct answer is: 5' RNA nucleotides, DNA nucleotides 3'

An Okazaki fragment has which of the following arrangements? Select one: a. DNA polymerase I, DNA polymerase III b. 3' RNA nucleotides, DNA nucleotides 5' c. 5' DNA to 3' d. 5' RNA nucleotides, DNA nucleotides 3'

Remember that C and G base pair and that A and T base pair. So, if the DNA sample is 42% cytosine, it must also be 42% guanine, because base pairing of cytosine and guanine requires that they be present in equal concentration. That means that 16% (100% - 42% - 42%) of the DNA sample must consist of A and T. Because A and T base pair with each other, they need to be present in equal amounts. So, the DNA sample must have 8% adenine and 8% thymine. The correct answer is: 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? Select one: a. 42% b. 8% c. 58% d. 16%

The correct answer is: origins of replication

DNA replication begins are special sites on the parental DNA molecule known as Select one: a. DNA polymerase binding sites b. Okazaki regions c. origins of replication d. primase binding sites

The correct answer is: origins of replication

DNA replication begins are special sites on the parental DNA molecule known as Select one: a. DNA polymerase binding sites b. origins of replication c. Okazaki regions d. primase binding sites

The correct answer is: origins of replication

DNA replication begins are special sites on the parental DNA molecule known as Select one: a. origins of replication b. primase binding sites c. Okazaki regions d. DNA polymerase binding sites

DNA polymerases can only add deoxyribonucleotides to the 3' end of an existing nucleotide chain. The correct answer is: DNA polymerases can only add deoxyribonucleotides to the 3' end of an existing nucleotide chain

Eukaryotic telomeres replicate differently than the rest of the chromosome. This is a consequence of which of the following? Select one: a. the "no ends" of a circular chromosome b. DNA polymerases can only add deoxyribonucleotides to the 3' end of an existing nucleotide chain c. DNA polymerases can only add deoxyribonucleotides to the 5' end of an existing nucleotide chain d. the evolution of telomerase enzyme

The correct answer is: part of nucleosomes

Histones are Select one: a. part of telomeres b. part of centromeres c. part of nucleosomes d. part of DNA replication origins

The correct answer is: proteins around which the DNA in chromosomes wrap

Histones are Select one: a. proteins that help unwind DNA prior to DNA replication b. proteins around which the DNA in chromosomes wrap c. proteins that bind solely to centromeres d. proteins that bind solely to telomeres

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 (i.e. the telomere). So, in most cells, our chromosomes get shorter with each round of DNA replication. There is some evidence that suggests that this shortening of our chromosomes is one of the processes that cause us to age. An enzyme known as "telomerase" is able to partially or fully restore the lengths of telomeres. Telomerase is especially active in germline cells, so that the chromosomes that people pass onto their children are approximately as long as the chromosomes they received from their parents. Some scientists feel that if we increased the activity of telomerase in the rest of our cells, all of our cells would maintain chromosomes of approximately their original length and the negative effects of chromosome (telomere) shortening that contribute towards aging would be reduced. In fact, although this hypothesis has not yet been tested in humans, telomere extension in mice and worms has been shown to reverse some signs of aging. The correct answer is: If telomerase activity was increased in our cells, the rate at which our chromosomes shorten as we age might be decreased.

How do some scientists feel that telomerase might be used to slow the aging process? Select one: a. If telomerase activity was decreased in our cells, the rate at which our chromosomes shorten as we age might be decreased. b. If telomerase activity was increased in our cells, the rate at which our chromosomes lengthen as we age might be decreased. c. If telomerase activity was decreased in our cells, the rate at which our chromosomes lengthen as we age might be decreased. d. If telomerase activity was increased in our cells, the rate at which our chromosomes shorten as we age might be decreased.

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 (i.e. the telomere). So, in most cells, our chromosomes get shorter with each round of DNA replication. There is some evidence that suggests that this shortening of our chromosomes is one of the processes that cause us to age. An enzyme known as "telomerase" is able to partially or fully restore the lengths of telomeres. Telomerase is especially active in germline cells, so that the chromosomes that people pass onto their children are approximately as long as the chromosomes they received from their parents. Some scientists feel that if we increased the activity of telomerase in the rest of our cells, all of our cells would maintain chromosomes of approximately their original length and the negative effects of chromosome (telomere) shortening that contribute towards aging would be reduced. In fact, although this hypothesis has not yet been tested in humans, telomere extension in mice and worms has been shown to reverse some signs of aging. The correct answer is: If telomerase activity was increased in our cells, the rate at which our chromosomes shorten as we age might be decreased.

How do some scientists feel that telomerase might be used to slow the aging process? Select one: a. If telomerase activity was increased in our cells, the rate at which our chromosomes lengthen as we age might be decreased. b. If telomerase activity was increased in our cells, the rate at which our chromosomes shorten as we age might be decreased. c. If telomerase activity was decreased in our cells, the rate at which our chromosomes shorten as we age might be decreased. d. If telomerase activity was decreased in our cells, the rate at which our chromosomes lengthen as we age might be decreased.

The correct answer is: 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

How do the nucleotides used to make RNA molecules differ from those used to make DNA molecules? Select one: a. the nucleotides used to make RNA molecules have ribose instead of deoxyribose as their sugar and two phosphate groups instead of three b. 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 c. 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 d. 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

DNA replication by a conservative, rather than the normal semi-conservative, model would mean that replication of a double-stranded DNA molecule would result in formation of two double-stranded DNA molecules, one of which would consist of two "parental" (i.e. original) DNA strands and the other of which would consist of two "daughter" (i.e. new) DNA strands. The correct answer is: 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

If an organism uses the "conservative" model of DNA replication, rather than the normal "semi-conservative" model of DNA replication, Select one: a. 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 b. after DNA replication occurs, each of the two double-stranded DNA molecules will consist of one "daughter" and one "parental" DNA strand c. each of the DNA strands in the double-stranded DNA molecules will consist of partly "parental" DNA and partly "daughter" DNA d. after DNA replication occurs, one of the DNA strands in each double-stranded DNA molecule will consist of a mixture of "daughter" and "parental" DNA and the other DNA strand in each double-stranded DNA molecule will consist of all "daughter" DNA

The correct answer is: in an antiparallel arrangement

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 Select one: a. covalently bound b. in an Okazaki arrangement c. homologously paired d. in an antiparallel arrangement

The correct answer is: histones.

In a nucleosome, the DNA is wrapped around Select one: a. ribosomes. b. polymerase molecules. c. satellite DNA. d. histones.

The correct answer is: There are two replication forks going in opposite directions.

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? Select one: a. Replication proceeds in one direction only. b. There are two replication forks going in opposite directions. c. Thymidine is only being added where the DNA strands are furthest apart. d. Thymidine is only added at the very beginning of replication.

The correct answer is: There are two replication forks going in opposite directions.

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? Select one: a. Thymidine is only added at the very beginning of replication. b. There are two replication forks going in opposite directions. c. Thymidine is only being added where the DNA strands are furthest apart. d. Replication proceeds in one direction only.

Replication of double-stranded DNA molecules occurs by what is known as the "semi-conservative" model. The DNA strands in the original double-stranded DNA molecule are known as the "parental" DNA strands. The DNA strands that are made by copying the parental DNA strands are known as the "daughter" DNA strands. According to the semiconservative model of DNA replication, each parental DNA strand is copied. So, after DNA replication occurs, each of the two resulting double-stranded DNA molecules consists of one parental DNA strand and one daughter DNA strand. In the example above, the nitrogen atoms in each of the parental DNA strands will be 15N, whereas the nitrogen atoms in each of the daughter strands will be 14N. Since each of the double-stranded DNA molecules that will be present after a round of replication will consist of one parental and one daughter DNA strand, each of these DNA molecules will have a weight that is half way in between the weight of DNA made entirely from 15N and the weight of DNA made entirely from 14N. The correct answer is: D

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? Select one: a. C b. D c. E d. B

Replication of double stranded DNA molecules occurs by the "semi-conservative" method. In this method, the two DNA strands of the original double-stranded DNA molecule unwind and are copied, so that the two resulting double-stranded DNA molecules each consist of a DNA strand from the original double-stranded DNA molecule (a "parental" strand) and a newly synthesized DNA strand (the "daughter" strand). So, if a bacterial cell replicates once, each of the two resulting cells will inherit a double-stranded DNA molecule where one strand is composed of the original parental DNA and the other strand will consist of newly synthesized DNA, which, because it was synthesized in the presence of radioactive nucleotides, will be radioactively labeled. The correct answer is: DNA in both daughter cells would be radioactive.

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? Select one: a. DNA in both daughter cells would be radioactive. b. Neither of the two daughter cells would be radioactive. c. One of the daughter cells, but not the other, would have radioactive DNA. d. All four bases of the DNA would be radioactive.

The correct answer is: the ends of linear chromosomes

Telomeres are Select one: a. attachment sites for the mitotic spindle apparatus b. part of the extracellular matrix c. the ends of linear chromosomes d. pores in the nuclear membrane that allow for passage of materials into and out of the nucleus

The correct answer is: sequence of bases

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

ATP and dATP are identical, except that ATP has ribose as its sugar and dATP has deoxyribose as its sugar. The correct answer is: the nucleoside triphosphates have the sugar deoxyribose; ATP has the sugar ribose.

The difference between ATP and the nucleoside triphosphates used during DNA synthesis is that Select one: a. ATP contains three high-energy bonds; the nucleoside triphosphates have two. b. the nucleoside triphosphates have two phosphate groups; ATP has three phosphate groups. c. triphosphate monomers are active in the nucleoside triphosphates, but not in ATP. d. the nucleoside triphosphates have the sugar deoxyribose; ATP has the sugar ribose.

ATP and dATP are identical, except that ATP has ribose as its sugar and dATP has deoxyribose as its sugar. The correct answer is: the nucleoside triphosphates have the sugar deoxyribose; ATP has the sugar ribose.

The difference between ATP and the nucleoside triphosphates used during DNA synthesis is that Select one: a. the nucleoside triphosphates have two phosphate groups; ATP has three phosphate groups. b. ATP contains three high-energy bonds; the nucleoside triphosphates have two. c. triphosphate monomers are active in the nucleoside triphosphates, but not in ATP. d. the nucleoside triphosphates have the sugar deoxyribose; ATP has the sugar ribose.

The correct answer is: depends on the action of DNA polymerase.

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

The correct answer is: telomeres

The ends of linear chromosomes are known as Select one: a. centromeres b. DNA replication origins c. telomeres d. endomeres

The correct answer is: 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 order in which chromatin packing occurs is as follows: Select one: a. 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 b. 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 c. 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 d. 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 pairs of nucleotides that interact to join together two DNA strands are known as complementary nucleotides. They are also sometimes called "complementary bases", since it is hydrogen bonds between the nitrogenous bases of nucleotides that holds together the two DNA strands in a double-stranded DNA molecule. The correct answer is: complementary nucleotides

The pairs of nucleotides that interact to join together two DNA strands are known as Select one: a. homozygous nucleotides b. partner nucleotides c. complementary nucleotides d. homologous nucleotides

Nucleotides are joined by a special type of condensation reaction known as a "dehydration" reaction. Dehydration reactions catalyze the formation of covalent bonds between nucleotides in a nucleotide chain. These bonds between nucleotides are known as "phosphodiester" bonds. The correct answer is: dehydration reaction

The reaction used to join together nucleotides to form a nucleotide chain is known as a Select one: a. dehydration reaction b. DNA catalysis reaction c. phosphodiesterase reaction d. hydrolysis reaction

The two strands of a double-stranded DNA molecule are held together by hydrogen bonds between the nitrogenous bases of the nucleotides. In DNA, the nitrogenous bases of guanine and cytosine interact to form three hydrogen bonds and the nitrogenous bases of adenine and thymine interact to form two hydrogen bonds. In RNA, the nitrogenous bases of guanine and cytosine interact to form three hydrogen bonds and the nitrogenous bases of adenine and uracil interact to form two hydrogen bonds. In the figure shown below, the hydrogen bonds are indicated by the red dotted lines between the bases. The correct answer is: hydrogen bonds

The two strands of a double-stranded DNA molecule are held together by Select one: a. hydrogen bonds b. ionic bonds c. nonpolar covalent bonds d. polar covalent bonds

The two strands of a double-stranded DNA molecule are held together by hydrogen bonds between complementary nitrogenous bases. In the figure shown below, the hydrogen bonds are indicated by the dotted red lines. The correct answer is: hydrogen bonds between complementary nitrogenous bases

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

The two strands of a double-stranded DNA molecule are held together by hydrogen bonds between the nitrogenous bases of the nucleotides. In DNA, the nitrogenous bases of guanine and cytosine interact to form three hydrogen bonds and the nitrogenous bases of adenine and thymine interact to form two hydrogen bonds. In RNA, the nitrogenous bases of guanine and cytosine interact to form three hydrogen bonds and the nitrogenous bases of adenine and uracil interact to form two hydrogen bonds. In the figure shown below, the hydrogen bonds are indicated by the red dotted lines between the bases. The correct answer is: hydrogen bonds

The two strands of a double-stranded DNA molecule are held together by Select one: a. nonpolar covalent bonds b. hydrogen bonds c. polar covalent bonds d. ionic bonds

The correct answer is: In E. coli, DNA polymerase I removes the RNA primers and fills in the resulting gaps with deoxyribonucleotides

What happens to the short RNA "primers" that primase synthesizes and that are extended by DNA polymerase III during DNA replication? Select one: a. DNA ligases join the RNA primers to DNA fragments to create a single, long nucleotide chain b. The RNA primers are unwound by helicases. c. In E. coli, DNA polymerase I removes the RNA primers and fills in the resulting gaps with deoxyribonucleotides d. DNA repair enzymes chemically modify the ribonucleotides so that they are converted to deoxyribonucleotides

Because DNA replication always occurs in the 5' to 3' direction, at each DNA replication fork multiple RNA primers will be needed for replication of one of the parental DNA strands at that fork, whereas replication of the other parental DNA strand at that fork will require only one RNA primer. The DNA strand that is synthesized using multiple RNA primers is known as the "lagging" strand whereas the DNA strand that can be synthesized using only one primer at the DNA fork is known as the "leading" strand. The short DNA fragments that are formed during synthesis of the lagging strand are known as "Okazaki" fragments. As DNA replication proceeds, specific DNA polymerases (DNA pol I in E. coli) remove the RNA primers at the beginning of each Okazaki fragment and fill in the resulting gaps with deoxyribonucleotides. DNA ligase then attaches the Okazaki fragments together. The correct answer is: DNA polymerase can join new nucleotides only to the 3' end of a growing strand.

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

Primase catalyzes the synthesis of short RNA "primers". DNA polymerase III than catalyzes the extension of those primers, adding deoxyribonucleotides to the 3' end of the RNA primer and forming DNA in the 5' to 3' direction. DNA polymerase I removes the RNA primers and fills in the resulting gaps. DNA ligase catalyzes the formation of covalent bonds between the ends of adjacent DNA fragments (i.e. Okazaki fragments), resulting in formation of a single, long DNA molecule. The correct answer is: to add nucleotides to the 3' end of a growing DNA strand

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

Primase catalyzes the synthesis of short RNA "primers". DNA polymerase III than catalyzes the extension of those primers, adding deoxyribonucleotides to the 3' end of the RNA primer and forming DNA in the 5' to 3' direction. DNA polymerase I removes the RNA primers and fills in the resulting gaps. DNA ligase catalyzes the formation of covalent bonds between the ends of adjacent DNA fragments (i.e. Okazaki fragments), resulting in formation of a single, long DNA molecule. The correct answer is: It joins DNA fragments together.

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

The paired bases of the DNA double helix are held together by hydrogen bonds between the nitrogenous bases of the nucleotides. In DNA, the nitrogenous bases of guanine and cytosine interact to form three hydrogen bonds and the nitrogenous bases of adenine and thymine interact to form two hydrogen bonds. In RNA, the nitrogenous bases of guanine and cytosine interact to form three hydrogen bonds and the nitrogenous bases of adenine and uracil interact to form two hydrogen bonds. In the figure shown below, the hydrogen bonds are indicated by the red dotted lines. The correct answer is: Hydrogen

What kind of chemical bond is found between paired bases of the DNA double helix? Select one: a. Covalent Incorrect b. Hydrogen c. Phosphate d. Ionic

Remember that nucleic acid chains bind with what is known as an "anti-parallel" arrangement, meaning that the 5' end of one chain is hydrogen-bonded to the 3' end of the other chain, and vice versa. Also remember that G and C base pair and that A and T base pair. Finally, remember that "U" is used in RNA, not DNA. So, after DNA replication, the double stranded DNA molecule will look like: 5' AAGGCTT 3' 3' TTCCGAA 5' So, the molecule that is synthesized is: 3' TTCCGAA 5' Writing this backwards, so that the new DNA molecule is written out in the conventional 5' to 3' direction, the molecule that is synthesized is: 5' AAGCCTT 3' The correct answer is: 5' AAGCCTT 3'

What would be the sequence of the DNA molecule made by replication of the DNA molecule shown below? 5' AAGGCTT 3' Select one: a. 5' TTCGGAA 3' b. 5' AAGCCUU 3' c. 5' AAGCCTT 3' d. 5' TTCCGAA 3'

Remember that nucleic acid chains bind with what is known as an "anti-parallel" arrangement, meaning that the 5' end of one chain is hydrogen-bonded to the 3' end of the other chain, and vice versa. Also remember that G and C base pair and that A and T base pair. Finally, remember that "U" is used in RNA, not DNA. So, after DNA replication, the double stranded DNA molecule will look like: 5' GCGAATA 3' 3' CGCTTAT 5' So, the molecule that is synthesized is: 3' CGCTTAT 5' Writing this backwards, so that the new DNA molecule is written out in the conventional 5' to 3' direction, the molecule that is synthesized is: 5' TATTCGC 3' The correct answer is: 5' TATTCGC 3'

What would be the sequence of the DNA molecule made by replication of the DNA molecule shown below? 5' GCGAATA 3' Select one: a. 5' UAUUCGC 3' b. 5' CGCTTAT 3' c. 5' CGCTTAT 3' d. 5' TATTCGC 3'

Remember that nucleic acid chains bind with what is known as an "anti-parallel" arrangement, meaning that the 5' end of one chain is hydrogen-bonded to the 3' end of the other chain, and vice versa. Also remember that G and C base pair and that A and T base pair. Finally, remember that "U" is used in RNA, not DNA. So, after DNA replication, the double stranded DNA molecule will look like: 5' TTCCGGA 3' 3' AAGGCCT 5' So, the molecule that is synthesized is: 3' AAGGCCT 5' Writing this backwards, so that the new DNA molecule is written out in the conventional 5' to 3' direction, the molecule that is synthesized is: 5' TTCCGGA 3' The correct answer is: 5' TCCGGAA 3'

What would be the sequence of the DNA molecule made by replication of the DNA molecule shown below? 5' TTCCGGA 3' Select one: a. 5' AAGGCCT 3' b. 5' UCCGGAA 3' c. 5' TCCGGAA 3' d. 5' AAGGCCT 3'

Primase catalyzes the synthesis of short RNA "primers". DNA polymerase III than catalyzes the extension of those primers, adding deoxyribonucleotides to the 3' end of the RNA primer and forming DNA in the 5' to 3' direction. DNA polymerase I removes the RNA primers and fills in the resulting gaps. DNA ligase catalyzes the formation of covalent bonds between the ends of adjacent DNA fragments (i.e. Okazaki fragments), resulting in formation of a single, long DNA molecule. The correct answer is: DNA polymerase III

Which enzyme catalyzes the elongation of a DNA strand in the 5' → 3' direction? Select one: a. primase b. DNA polymerase III c. DNA ligase d. topoisomerase

The correct answer is: 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

Which of the following describes the sequence of events that occurs during DNA replication of a double-stranded DNA molecule? Select one: a. separation of the DNA strands at DNA replication origins, synthesis of RNA primers, synthesis of DNA, ligation of DNA fragments, unwinding of DNA b. 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 c. 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 d. 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

DNA polymerases only add nucleotides to the end of an existing nucleotide chain. So, DNA synthesis is initiated by an enzyme called primase, which catalyzes the formation of a short RNA primer, using the DNA molecule being copied as a template. DNA polymerase III is then able to catalyze the addition of deoxyribonucleotides to the 3' end of the RNA primer. Different DNA polymerases (DNA polymerase I in E. coli) then remove the RNA primers and fill in the resulting gaps with deoxyribonucleotides. The correct answer is: primase

Which of the following enzymes initiates the synthesis of a new nucleotide chain during DNA replication? Select one: a. primase b. DNA polymerase II c. DNA polymerase I d. DNA polymerase III

DNA polymerases only add nucleotides to the end of an existing nucleotide chain. So, DNA synthesis is initiated by an enzyme called primase, which catalyzes the formation of a short RNA primer, using the DNA molecule being copied as a template. DNA polymerase III is then able to catalyze the addition of deoxyribonucleotides to the 3' end of the RNA primer. Different DNA polymerases (DNA polymerase I in E. coli) then remove the RNA primers and fill in the resulting gaps with deoxyribonucleotides. The correct answer is: primase

Which of the following enzymes initiates the synthesis of a new nucleotide chain during DNA replication? Select one: a. primase b. DNA polymerase I c. DNA polymerase II d. DNA polymerase III

Primase catalyzes the synthesis of short RNA "primers". DNA polymerase III than catalyzes the extension of those primers, adding deoxyribonucleotides to the 3' end of the RNA primer and forming DNA in the 5' to 3' direction. In E. coli, DNA polymerase I removes the RNA primers and fills in the resulting gaps. DNA ligase catalyzes the formation of covalent bonds between the ends of adjacent DNA fragments (i.e. Okazaki fragments), resulting in formation of a single, long DNA molecule. The correct answer is: primase

Which of the following enzymes synthesizes short segments of RNA? Select one: a. ligase b. DNA polymerase III c. primase d. DNA polymerase I

G pairs with C A pairs with T U is found in RNA, not DNA The correct answer is: C with G

Which of the following shows the correct base pairing of deoxyribonucleotides that occurs in nature? Select one: a. C with A b. C with G c. C with U d. C with T

G pairs with C A pairs with U T is found in DNA, not RNA The correct answer is: U with A

Which of the following shows the correct base pairing of ribonucleotides that occurs in nature? Select one: a. U with A b. U with T c. U with G d. U with C

Histones are protein molecules that help package DNA. Chromatin is the mixture of DNA and proteins that forms chromosomes. Histones are important components of chromatin. The correct answer is: Histones help transport mRNA molecules out of the nucleus

Which of the following statements about histones is FALSE? Select one: a. Histones help package DNA b. Histones are composed of amino acids c. Histones are an important component of chromatin d. Histones help transport mRNA molecules out of the nucleus

Eukaryotic chromosomes consist of a single, linear DNA molecule that is complexed together with proteins. The structure of chromosomes is determined more by the proteins that are part of the chromosome than by the nucleotide sequence of the DNA molecule. The correct answer is: It consists of a single linear molecule of double-stranded DNA plus proteins.

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

The correct answer is: all of these statements are true

Which of the following statements regarding DNA polymerases is TRUE? Select one: a. all of these statements are true b. DNA polymerases can add nucleotides to the 3' end of an RNA molecule c. DNA polymerases can only add nucleotides to the 3' end of a nucleotide chain d. DNA polymerases can NOT initiate synthesis of a new deoxyribonucleotide chain

DNA polymerases only add nucleotides to the end of an existing nucleotide chain. So, DNA synthesis is initiated by an enzyme called primase, which catalyzes the formation of a short RNA primer, using the DNA molecule being copied as a template. DNA polymerase III is then able to catalyze the addition of deoxyribonucleotides to the 3' end of the RNA primer. Different DNA polymerases (DNA polymerase I in E. coli) then remove the RNA primers and fill in the resulting gaps with deoxyribonucleotides. The correct answer is: DNA polymerases can not initiate synthesis of new nucleotide chains

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

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 (i.e. the telomere). So, in most cells, our chromosomes get shorter with each round of DNA replication. However, an enzyme known as "telomerase" is able to partially of fully restore the lengths of telomeres. Telomerase is especially active in germline cells, so that the chromosomes that people pass onto their children are approximately as long as the chromosomes they received from their parents. So, while the chromosomes in most of your cells will get shorter as you age, the chromosomes you pass onto your children should have their original lengths. The correct answer is: 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.

Will the chromosomes you pass onto your children be shorter than your chromosomes? Select one: a. 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. b. No, because DNA repair enzymes will fill in any missing gaps at the ends of your chromosomes. c. Yes, because DNA polymerase is not able to fully replicate the ends of chromosomes. d. Yes, because DNA repair enzymes do not function properly in germline cells (the cells that produce egg or sperm cells).

The short DNA fragments likely represent Okazaki fragments. Okazaki fragments are the short DNA fragments that are made as the lagging DNA strand is synthesized. Remember that nucleotide chains are always synthesized in the 5' to 3' direction and that DNA polymerases only add nucleotides to the end of an existing nucleotide chain. So, DNA synthesis is initiated by an enzyme called primase, which catalyzes the formation of a short RNA primer, using the DNA molecule being copied as a template. DNA polymerase III then catalyzes the addition of deoxyribonucleotides to the 3' end of the RNA primer. So, short nucleotide chains are formed during synthesis of the lagging strand. In contrast, synthesis of the other DNA strand, the "leading" strand, can occur continuously. So, the very large DNA molecules are likely to consist of leading strands. The correct answer is: leading strands and Okazaki fragments.

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 Select one: a. lagging strands and Okazaki fragments. b. Okazaki fragments and RNA primers. c. leading strands and RNA primers. d. leading strands and Okazaki fragments.

As we age, our chromosomes become shorter because cells are not fully able to replicate the ends of linear chromosomes (i.e. the telomeres). As we age, the frequency of mutations in our DNA is likely to become greater, not smaller. RNA fragments are unlikely to accumulate in your DNA as such RNA fragments will be removed by special DNA polymerases. The correct answer is: Your chromosomes will become shorter.

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