Chapter 16 molecular basis of inheritance

A

After a region of DNA has been replicated, ______ removes the RNA primers. A. DNA polymerase I B. DNA polymerase III C. DNA helicase D. RNA primase E. DNA ligas

D

After removal of the RNA primers and replacement with DNA nucleotides, the single-stranded nick adjacent to Okazaki fragments is filled in through a reaction that involves which enzyme? A. DNA primase B. Single strand binding protein C. RNA polymerase D. DNA ligase E. DNA helicase

C

After the formation of replication bubbles, which of the following is the correct sequence of enzyme use for the synthesis of the lagging DNA strand? A. primase, helicases, DNA polymerase III, DNA polymerase I, ligase B. helicases, primase, ligase, DNA polymerase I, DNA polymerase III C. helicases, primase, DNA polymerase III, DNA polymerase I, ligase D. helicases, DNA polymerase III, DNA polymerase I, primase, ligase E. ligase, primase, DNA polymerase III, helicases, DNA polymerase I

D

As helicase unwinds the DNA molecule, what keeps the strands apart? A. DNA polymerase B. Reverse transcriptase C. Replication fork D. Single-strand binding proteins E. Okazaki fragments

B

Where does the initiator protein bind DNA at the start of replication? A. At a replication fork B. At an origin of replication C. At any AT-rich region D. At a promoter region E. At a start codo

A

Which of the following is LEAST related to the others in the list? A. promoter B. ligase C. primase D. helicase E. DNA polymerase

D

catalyzes synthesis of a new strand of DNA. A. helicase B. exonuclease C. ligase D. DNA polymerase III E. primase

B

Chargaff found that for DNA A. the ratio of A to C is close to 1:1 and the ratio of G to T is close to 1:1. B. the ratio of A to T is close to 1:1 and the ratio of G to C is close to 1:1. C. the ratio of A to G is close to 1:1 and the ratio of T to C is close to 1:1. D. A + T = G + C. E. A + G > T + C.

A

Chemicals from heat-killed S cells were purified. The chemicals were tested for the ability to transform live R cells. The transforming agent was found to be DNA. A. Griffith B. Hershey and Chase C. Avery, MacLeod, and McCarty D. Chargaff E. Meselson and Stahl

E

DNA ligase functions in A. elongation of the leading strand. B. elongation of the lagging strand by joining Okazaki fragments C. DNA repair D. unwinding of the double helix. E. Both B and C are correct

E

DNA replication is said to be semiconservative. This means that A. half of the old strand is degraded and half is used as a template for the replication of a new strand. B. one of the two resulting double helices is made of 2 old strands and the other is made of 2 new strands. C. the old double helix is degraded and half of its nucleotides are used in the construction of two new double helices. D. one strand of the new double helix is made of DNA and the other strand is made of RNA. E. each new double helix consists of 1 old and 1 new strand

E

Damaged DNA is excised and repaired by A. restriction enzymes. B. ligase. C. primase. D. DNA polymerase I. E. both DNA polymerase I and ligase

A

During replication, the direction of synthesis of new DNA from the leading and lagging strands is A. 5′ to 3′ only. B. 3′ to 5′ only. C. from left to right only. D. both 5′ to 3′ and 3′ to 5′. E. different, depending on whether the cell is prokaryotic or eukaryotic

Tapoisomerase

Relieves over winding, by breaking, swiveling and rejoining DNA strands

DNA Pol I

Removes RNA nucleotides of primer from 5' end and replaces them with DNA nucleotides

E

Scientists have discovered how to put together a bacteriophage with the protein coat of phage T2 and the DNA of phage T4. If this composite phage were allowed to infect a bacterium, the phages produced in the host cell would have A. the protein of T2 and the DNA of T4. B. the protein of T4 and the DNA of T2. C. a mixture of the DNA and proteins of both phages. D. the protein and DNA of T2. E. the protein and DNA of T4.

Primase I

Synthesizes RNA primer at 5'end of leading strand and of each okazaki fragment of lagging strand. Removes RNA primer

D

Telomeres A. get longer with continued cell division. B. are found in both prokaryotic and eukaryotic cells. C. remain the same regardless of the frequency of cell division. D. get shorter with continued cell division. E. Are shorter for younger individuals.

B

The DNA of a phage was injected into the bacterial host, but the protein coat stayed outside. The viral DNA directed the host to replicate new phage viruses A. Griffith B. Hershey and Chase C. Avery, MacLeod, and McCarty D. Chargaff E. Meselson and Stahl

B

The X-ray diffraction studies conducted by ______ were key to the discovery of the structure of DNA. A. McClintock B. Franklin C. Meselson and Stahl D. Chargaff E. Griffith

B

The new DNA strand being produced in the 5' to 3' direction is called the _____ strand. A. Okazaki B. leading C. bubble D. lagging E. new

D

The problem of replicating the lagging strand--that is, adding bases in the 3'- 5' direction--is solved by making A. base pairing. B. replication forks. C. the unwinding enzyme, helicase. D. Okazaki fragments. E. topoisomerases.

C

covalently connects segments of DNA A. helicase B. exonuclease C. ligase D. DNA polymerase III E. primase

A

enhances separation of DNA strands during replication A. helicase B. exonuclease C. ligase D. DNA polymerase III E. primase

B

involved in repair of damage to DNA A. helicase B. exonuclease C. ligase D. DNA polymerase III E. primase

E

synthesizes short segments of RNA. A. helicase B. exonuclease C. ligase D. DNA polymerase III E. primase

A

What is the primer that is required to initiate the synthesis of a new DNA strand? A. a small piece of RNA B. a small piece of DNA C. protein D. ligase E. primase

Single-strand binding protein

Binds to and stabilizes single stranded DNA until it can be used as a template (holds DNA apart)

C

How many replication forks are produced when DNA denatures at an origin? A. 0 B. 1 C. 2 D. 3 E. The number varies

C

If cytosine makes up 22% of the nucleotides in a sample of DNA from an organism, then adenine would make up what percent of the bases? A. 22 B. 44 C. 28 D. 56 E. It cannot be determined from the information provided.

A

If radioactive phosphorus (32p) is used in the culture medium of bacteria that harbor phage viruses, it will later appear in the A. viral DNA. B. bacterial RNA. C. viral coats. D. viral RNA. E. bacterial cell wall

C

If radioactive sulfur (35S) is used in the culture medium of bacteria that harbor phage viruses, it will later appear in the A. viral DNA. B. bacterial RNA. C. viral coats. D. viral RNA. E. bacterial cell wall.

E

In Griffith's experiments, a harmless variant of S. pneumoniae became pathogenic when mixed with a heat-killed pathogenic variant as a result of A. conjugation. B. transduction. C. mutation. D. natural selection. E. transformation.

C

In an analysis of the nucleotide composition of DNA to see which bases are equivalent in concentration, which of the following would be TRUE? A. A=C B. A=G and C=T C. A+C=G+T D. A+T=G+C E. Both B and C are true

D

In any DNA sample, the amount of adenine equals the amount of thymine and the amount of guanine equals the amount of cytosine A. Griffith B. Hershey and Chase C. Avery, MacLeod, and McCarty D. Chargaff E. Meselson and Stahl

B

In both prokaryotes and eukaryotes, DNA replication is A. unidirectional and dispersive. B. bidirectional and semiconservative. C. unidirectional and semiconservative. D. dispersive and semiconservative. E. bidirectional and dispersive.

DNA Ligase

Joins 3' end of DNA that replaces primer to rest of leading strand and joins okazaki fragments of lagging strand. Covalently connect segments of DNA

C

What is the function of DNA polymerase III in E. coli? A. to unwind the DNA helix during replication B. to seal together the broken ends of DNA strands C. to add nucleotides to the end of a growing DNA strand D. to degrade damaged DNA molecules E. to rejoin the two DNA strands (one new and one old) after replication

E

The two most basic steps of DNA replication are A. primase causes primer to bind template and ligase copies the template. B. helicase unwinds template and DNA polymerase binds. C. leading strand is copied first and lagging strand second. D. the new strand is denatured and a template is synthesized. E. the template strands are denatured (separated ) and a new strand is synthesized

D

The two strands of a DNA double helix are antiparallel. This means that A. the two strands are mirror images. B. only one of the two strands can be used as a template for replication, since DNA polymerase only works in one direction. C. one strand is actually composed of RNA. D. one strand runs in the 5'Æ3' direction and the other runs in the 3' Æ5' direction. E. they both run in the 3'Æ5' direction

Helicase

Unwinds parental double helix of replication, separates the DNA strands during replication

DNA Pol III

Uses parental DNA as a template, synthesizes new DNA strand by covalently adding nucleotides to 3' end of pre existing DNA strand and RNA primer

A

What allows for the base-pairing error rate to be kept very low during replication? A. DNA repair mechanisms can fix the mispaired bases. B. Bases that are mispaired can excise themselves. C. UV light radiation corrects any base mispairs. D. There are no errors. E. Mispaired bases cause the cell to die.

D

What is a replication bubble? A. A complex of replication enzymes on the DNA template strand B. A DNA sequence that initiates replication C. A tangle of denatured DNA strands near the replication fork D. A locally denatured segment of DNA where replication originates E. A localized site in the nucleus where chromosomes are replicating

C

When a double-stranded DNA molecule is heated, it denatures into two single-stranded molecules. The reason for this is that A. the proteins associated with the double helix are denatured and can no longer hold the DNA strands together. B. the heat causes the helix to straighten, breaking the connections between the bases. C. the heat breaks the hydrogen bonds holding the bases together in the center of the molecule but does not affect the covalent bonds of the backbone. D. the heat denatures the bases, preventing them from hydrogen-bonding with each other. E. the heat causes the phosphate groups to ionize, preventing them from hydrogen-bonding to the bases.

E

Which enzyme activity is associated with DNA polymerase I? A. 5′ to 3′ exonuclease B. 3′ to 5′ exonuclease C. 5′ to 3′ polymerase D. Both A and B E. All of the above

C

Which enzyme catalyzes the elongation of a DNA strand in the 5'- 3' direction? A. primase B. DNA ligase C. DNA polymerase III D. topoisomerase E. helicase

B

Which enzyme elongates the new DNA strand starting at an RNA primer? A. DNA polymerase I B. DNA polymerase III C. RNA primase D. DNA ligase E. RNA polymerase

E

Which kind of enzyme prevents DNA from supercoiling replication fork migrates during replication? A. Helicase B. Ligase C. DNA polymerase I D. DNA polymerase III E. Topoisomerase (gyrase)

C

Which of the following are necessary for DNA replication? A. RNA, helicase, DNA polymerases B. Okazaki fragments, helicase, DNA polymerases C. Template DNA, DNA polymerases and four dNTPs (nucleotides) D. Template DNA and four dNTPs E. Template DNA, four dNTPs and RNA polymeras

C

Which of the following descriptions best fits the class of molecules known as nucleotides? A. a nitrogen base and a phosphate group only B. a nitrogen base and a five-carbon sugar only C. a nitrogen base, a phosphate group, and a five-carbon sugar D. a five-carbon sugar, a phosphate group, and an inorganic base E. a pyrimidine, a purine, and a six-carbon sugar

D

Which of the following help to hold the DNA strands apart while they are being replicated? A. helicase B. ligase C. DNA polymerase D. single-stranded binding proteins E. exonuclease

D

Which of the following is correct? A. A forms 2 hydrogen bonds with G; T forms 3 hydrogen bonds with C. B. A forms 3 hydrogen bonds with T; G forms 2 hydrogen bonds with C. C. A forms 2 covalent bonds with T; G forms 3 covalent bonds with C. D. A forms 2 hydrogen bonds with T; G forms 3 hydrogen bonds with C. E. A forms 3 covalent bonds with T; G forms 2 covalent bonds with C

E

Which of the following is not true of DNA? A. A pairs with T and G pairs with C. B. Nitrogen bases are 0.34 nm apart on a DNA strand. C. The double helix is 2.0 nm wide. D. Its purine bases are larger than its pyrimidine bases. E. Each turn of the double helix is 4.3 nm long.

D

Which of the following statements does NOT apply to the Watson and Crick model of DNA? A. The two strands of the DNA helix are antiparallel. B. The helix is 2 nm in width. C. The framework of the helix consists of sugar-phosphate units of the nucleotides. D. The two strands of the helix are held together by covalent bonds. E. The purines are attracted to pyrimidines.

A

_______ is the fixing of mistakes made during DNA replication; ______ is the fixing of damage to a pre-existing double helix. A. Mismatch repair . . . excision repair B. Leading . . . lagging C. Operon repair . . . histone repair D. Transformation . . . transduction E. Proto-oncogene repair . . . oncogene