Chapter 6, Problem 1P

Griffith, in his 1928 experiments, demonstrated that bacterial strains could be genetically transformed. The evidence that DNA was the transforming principle responsible for this phenomenon came later. What was the key experiment that Avery, MacCleod, and McCarty performed to prove that DNA was responsible for the genetic change from rough cells into smooth cells?

Summary Introduction

a.

To determine:

The phrase that describes “transformation” among the options given below.

1. the strand that is synthesized discontinuously during replication
2. the sugar within the nucleotide subunits of DNA
3. a nitrogenous base containing a double ring
4. noncovalent bonds that hold the two strands of the double helix together
5. Meselson and Stahl experiment
6. Griffith experiment
7. structures at ends of eukaryotic chromosomes
8. two nitrogenous bases that can pair via hydrogen bonds
9. catalyzes site-specific recombination
10. a nitrogenous base containing a single ring
11. a short sequence of bases w here unw inding of the double helix for replication begins
12. a virus that infects bacteria
13. short DNA fragments formed by discontinuous replication of one of the strands
14. enzymes involved in controlling DNA supercoiling

Introduction:

transformation is one of the mechanisms by which bacteria transfer genes from one strain to another. It occurs when DNA from a donor is added to the bacterial growth medium and is then taken up from the medium by the recipient. The recipient cell is called a transformant.

Answer to Problem 1P

Correct answer:

Transformation: Griffith experiment

Explanation of Solution

Griffith experiment shows that the transformation is the process of alteration of cellular genetics. This can be done by the incorporation of the exogenous material into the genetic makeup of an organism.

Summary Introduction

b.

To determine:

The phrase that describes “bacteriophage” among the options given below.

1. the strand that is synthesized discontinuously during replication
2. the sugar within the nucleotide subunits of DNA
3. a nitrogenous base containing a double ring
4. noncovalent bonds that hold the two strands of the double helix together
5. Meselson and Stahl experiment
6. Griffith experiment
7. structures at ends of eukaryotic chromosomes
8. two nitrogenous bases that can pair via hydrogen bonds
9. catalyzes site-specific recombination
10. a nitrogenous base containing a single ring
11. a short sequence of bases w here unw inding of the double helix for replication begins
12. a virus that infects bacteria
13. short DNA fragments formed by discontinuous replication of one of the strands
14. enzymes involved in controlling DNA supercoiling

Introduction:

Bacteriophage a virus for which the natural host is a bacterial cell. They are known as bacteria-eaters.

Answer to Problem 1P

Correct answer:

Bacteriophage: A virus that infects bacteria

Explanation of Solution

A bacteriophage is a type of virus that infects bacteria. This virus is made up of nucleic acid molecule which is surrounded by a protein layer called capsid.

Summary Introduction

c.

To determine:

1. the strand that is synthesized discontinuously during replication
2. the sugar within the nucleotide subunits of DNA
3. a nitrogenous base containing a double ring
4. noncovalent bonds that hold the two strands of the double helix together
5. Meselson and Stahl experiment
6. Griffith experiment
7. structures at ends of eukaryotic chromosomes
8. two nitrogenous bases that can pair via hydrogen bonds
9. catalyzes site-specific recombination
10. a nitrogenous base containing a single ring
11. a short sequence of bases w here unw inding of the double helix for replication begins
12. a virus that infects bacteria
13. short DNA fragments formed by discontinuous replication of one of the strands
14. enzymes involved in controlling DNA supercoiling

Introduction:

pyrimidines are a chemical group that includes the nitrogenous bases cytosine, thymine, and uracil.

Answer to Problem 1P

Correct answer:

Pyrimidine: A nitrogenous base containing a single ring

Explanation of Solution

Pyrimidine is a nitrogenous base that consists of two nitrogen and four carbons. It is a single ring structure. It catalyzes site-specific recombination.

Summary Introduction

d.

To determine:

1. the strand that is synthesized discontinuously during replication
2. the sugar within the nucleotide subunits of DNA
3. a nitrogenous base containing a double ring
4. noncovalent bonds that hold the two strands of the double helix together
5. Meselson and Stahl experiment
6. Griffith experiment
7. structures at ends of eukaryotic chromosomes
8. two nitrogenous bases that can pair via hydrogen bonds
9. catalyzes site-specific recombination
10. a nitrogenous base containing a single ring
11. a short sequence of bases w here unw inding of the double helix for replication begins
12. a virus that infects bacteria
13. short DNA fragments formed by discontinuous replication of one of the strands
14. enzymes involved in controlling DNA supercoiling

Introduction:

Deoxyribose is a molecule similar to ribose, except that the 2′ carbon has a hydrogen rather than a hydroxyl group.

Answer to Problem 1P

Correct answer:

Deoxyribose: The sugar within the nucleotide subunits of DNA

Explanation of Solution

Deoxyribose is the pentose sugar that forms the backbone of DNA. This sugar is derived from ribose sugar by loss of oxygen molecule.

Summary Introduction

e.

To determine:

1. the strand that is synthesized discontinuously during replication
2. the sugar within the nucleotide subunits of DNA
3. a nitrogenous base containing a double ring
4. noncovalent bonds that hold the two strands of the double helix together
5. Meselson and Stahl experiment
6. Griffith experiment
7. structures at ends of eukaryotic chromosomes
8. two nitrogenous bases that can pair via hydrogen bonds
9. catalyzes site-specific recombination
10. a nitrogenous base containing a single ring
11. a short sequence of bases w here unw inding of the double helix for replication begins
12. a virus that infects bacteria
13. short DNA fragments formed by discontinuous replication of one of the strands
14. enzymes involved in controlling DNA supercoiling

Introduction:

Hydrogen bonds are weak electrostatic bonds that result in a partial sharing of hydrogen atoms between reacting groups.

Answer to Problem 1P

Correct answer:

Hydrogen bonds: Noncovalent bonds that hold the two strands of the double helix together

Explanation of Solution

Hydrogen bond is an electrostatic bond that occur between a hydrogen atom and a more electronegative atom. These bonds are responsible for holding the strands of DNA double helix together.

Summary Introduction

f.

To determine:

The phrase that describes “complementary bases” among the options given below.

1. the strand that is synthesized discontinuously during replication
2. the sugar within the nucleotide subunits of DNA
3. a nitrogenous base containing a double ring
4. noncovalent bonds that hold the two strands of the double helix together
5. Meselson and Stahl experiment
6. Griffith experiment
7. structures at ends of eukaryotic chromosomes
8. two nitrogenous bases that can pair via hydrogen bonds
9. catalyzes site-specific recombination
10. a nitrogenous base containing a single ring
11. a short sequence of bases w here unw inding of the double helix for replication begins
12. a virus that infects bacteria
13. short DNA fragments formed by discontinuous replication of one of the strands
14. enzymes involved in controlling DNA supercoiling

Introduction:

Complementarity is the property of DNA whereby the base sequences of the two strands in the double helix are reverse complements of one another; A is opposite T, and G is opposite C.

Answer to Problem 1P

Correct answer:

Complementary bases: Two nitrogenous bases that can pair via hydrogen bonds

Explanation of Solution

The complementary bases are the two base pairs that are connected with the help of hydrogen bonds in the DNA strands.

Summary Introduction

g.

To determine:

The phrase that describes “origin” among the options given below.

1. the strand that is synthesized discontinuously during replication
2. the sugar within the nucleotide subunits of DNA
3. a nitrogenous base containing a double ring
4. noncovalent bonds that hold the two strands of the double helix together
5. Meselson and Stahl experiment
6. Griffith experiment
7. structures at ends of eukaryotic chromosomes
8. two nitrogenous bases that can pair via hydrogen bonds
9. catalyzes site-specific recombination
10. a nitrogenous base containing a single ring
11. a short sequence of bases w here unw inding of the double helix for replication begins
12. a virus that infects bacteria
13. short DNA fragments formed by discontinuous replication of one of the strands
14. enzymes involved in controlling DNA supercoiling

Introduction:

The model of DNA replication was proposed by the scientists Watson and Crick. Unwinding of the double helix enables each of the two parental strands to function as a template for the synthesis of a new strand by the mechanism of complementary base pairing. As a result a single double helix is converted into two identical daughter double helixes

Answer to Problem 1P

Correct answer:

Origin: A short sequence of bases where unwinding of the double helix for replication begins

Explanation of Solution

Origin is a sequence of bases from where the DNA double helix unwinds. It is the point from where process of replication is initiated.

Summary Introduction

h.

To determine:

The phrase that describes “okazaki fragments” among the options given below.

1. the strand that is synthesized discontinuously during replication
2. the sugar within the nucleotide subunits of DNA
3. a nitrogenous base containing a double ring
4. noncovalent bonds that hold the two strands of the double helix together
5. Meselson and Stahl experiment
6. Griffith experiment
7. structures at ends of eukaryotic chromosomes
8. two nitrogenous bases that can pair via hydrogen bonds
9. catalyzes site-specific recombination
10. a nitrogenous base containing a single ring
11. a short sequence of bases w here unw inding of the double helix for replication begins
12. a virus that infects bacteria
13. short DNA fragments formed by discontinuous replication of one of the strands
14. enzymes involved in controlling DNA supercoiling

Introduction:

Okazaki fragments are formed during DNA replication. They are small fragments of about 1000 bases that are joined after synthesis to form the lagging strand.

Answer to Problem 1P

Correct answer:

Okazaki fragments: Short DNA fragments formed by discontinuous replication of one of the strands.

Explanation of Solution

Okazaki fragments are the short stretch of DNA fragments which are formed by the discontinuous replication of one DNA strand.

Summary Introduction

i.

To determine:

The phrase that describes “purine” among the options given below.

1. the strand that is synthesized discontinuously during replication
2. the sugar within the nucleotide subunits of DNA
3. a nitrogenous base containing a double ring
4. noncovalent bonds that hold the two strands of the double helix together
5. Meselson and Stahl experiment
6. Griffith experiment
7. structures at ends of eukaryotic chromosomes
8. two nitrogenous bases that can pair via hydrogen bonds
9. catalyzes site-specific recombination
10. a nitrogenous base containing a single ring
11. a short sequence of bases w here unw inding of the double helix for replication begins
12. a virus that infects bacteria
13. short DNA fragments formed by discontinuous replication of one of the strands
14. enzymes involved in controlling DNA supercoiling

Introduction:

Purines are a chemical group that includes the nitrogenous bases adenine and guanine.

Answer to Problem 1P

Correct answer:

Purine: A nitrogenous base containing a double ring

Explanation of Solution

The nitrogenous bases that contains double ring are purines. Adenine and guanine are the two types of purines present in double stranded DNA molecule.

Summary Introduction

j.

To determine:

The phrase that describes “topoisomerases” among the options given below.

1. the strand that is synthesized discontinuously during replication
2. the sugar within the nucleotide subunits of DNA
3. a nitrogenous base containing a double ring
4. noncovalent bonds that hold the two strands of the double helix together
5. Meselson and Stahl experiment
6. Griffith experiment
7. structures at ends of eukaryotic chromosomes
8. two nitrogenous bases that can pair via hydrogen bonds
9. catalyzes site-specific recombination
10. a nitrogenous base containing a single ring
11. a short sequence of bases w here unw inding of the double helix for replication begins
12. a virus that infects bacteria
13. short DNA fragments formed by discontinuous replication of one of the strands
14. enzymes involved in controlling DNA supercoiling

Introduction:

DNA topoisomerases are a group of enzymes that assist relax supercoiling of the DNA helix by nicking one or both strands to allow the strands to rotate relative to each other.

Answer to Problem 1P

Correct answer:

Topoisomerases: Enzymes involved in controlling DNA supercoiling

Explanation of Solution

Topoisomerases are the group of enzymes which are involved in the over winding or under winding of the DNA. It controls the super coiling of double stranded DNA molecule.

Summary Introduction

k.

To determine:

The phrase that describes “semiconservative replication” among the options given below.

1. the strand that is synthesized discontinuously during replication
2. the sugar within the nucleotide subunits of DNA
3. a nitrogenous base containing a double ring
4. noncovalent bonds that hold the two strands of the double helix together
5. Meselson and Stahl experiment
6. Griffith experiment
7. structures at ends of eukaryotic chromosomes
8. two nitrogenous bases that can pair via hydrogen bonds
9. catalyzes site-specific recombination
10. a nitrogenous base containing a single ring
11. a short sequence of bases w here unw inding of the double helix for replication begins
12. a virus that infects bacteria
13. short DNA fragments formed by discontinuous replication of one of the strands
14. enzymes involved in controlling DNA supercoiling

Introduction:

semiconservative replication is a mechanism of DNA replication in which each single strand of the parent double helix functions as template for synthesis of its complement. As a result two daughter double helixes that each contain one of the original DNA strands intact (conserved) and one completely new strand is produced.

Answer to Problem 1P

Correct answer:

Semiconservative replication: Meselson and Stahl experiment

Explanation of Solution

Meselson and Stahl experiment describe the semi conservative replication in which both the daughter strands have a copy of parent strand.

Summary Introduction

l.

To determine:

1. the strand that is synthesized discontinuously during replication
2. the sugar within the nucleotide subunits of DNA
3. a nitrogenous base containing a double ring
4. noncovalent bonds that hold the two strands of the double helix together
5. Meselson and Stahl experiment
6. Griffith experiment
7. structures at ends of eukaryotic chromosomes
8. two nitrogenous bases that can pair via hydrogen bonds
9. catalyzes site-specific recombination
10. a nitrogenous base containing a single ring
11. a short sequence of bases w here unw inding of the double helix for replication begins
12. a virus that infects bacteria
13. short DNA fragments formed by discontinuous replication of one of the strands
14. enzymes involved in controlling DNA supercoiling

Introduction:

During replication, the DNA strand replicated discontinuously, 5′ to 3′ away from the Y-shaped replication fork, as small Okazaki fragments that are ultimately joined into a continuous strand.

Answer to Problem 1P

Correct answer:

Lagging strand: The strand that is synthesized discontinuously during replication

Explanation of Solution

Lagging strand is the type of strand that is synthesized discontinuously. It consist of short DNA fragments that are synthesized during the process of DNA replication.

Summary Introduction

m.

To determine:

The phrase that describes “telomeres” among the options given below.

1. the strand that is synthesized discontinuously during replication
2. the sugar within the nucleotide subunits of DNA
3. a nitrogenous base containing a double ring
4. noncovalent bonds that hold the two strands of the double helix together
5. Meselson and Stahl experiment
6. Griffith experiment
7. structures at ends of eukaryotic chromosomes
8. two nitrogenous bases that can pair via hydrogen bonds
9. catalyzes site-specific recombination
10. a nitrogenous base containing a single ring
11. a short sequence of bases w here unw inding of the double helix for replication begins
12. a virus that infects bacteria
13. short DNA fragments formed by discontinuous replication of one of the strands
14. enzymes involved in controlling DNA supercoiling

Introduction:

Telomeres are specialized terminal structures on eukaryotic chromosomes that ensure the regulation and accurate replication of the two ends of each linear chromosome.

Answer to Problem 1P

Correct answer:

Telomeres: Structures at ends of eukaryotic chromosomes

Explanation of Solution

Telomeres are the structures which are present at the end of the chromosome. These are the cap like structures that protect the chromosome.

Summary Introduction

n.

To determine:

The phrase that describes “recombinase” among the options given below.

1. the strand that is synthesized discontinuously during replication
2. the sugar within the nucleotide subunits of DNA
3. a nitrogenous base containing a double ring
4. noncovalent bonds that hold the two strands of the double helix together
5. Meselson and Stahl experiment
6. Griffith experiment
7. structures at ends of eukaryotic chromosomes
8. two nitrogenous bases that can pair via hydrogen bonds
9. catalyzes site-specific recombination
10. a nitrogenous base containing a single ring
11. a short sequence of bases w here unw inding of the double helix for replication begins
12. a virus that infects bacteria
13. short DNA fragments formed by discontinuous replication of one of the strands
14. enzymes involved in controlling DNA supercoiling

Introduction:

Recombinase is an enzyme that carries out site-specific recombination

Answer to Problem 1P

Correct answer:

Recombinase: Catalyzes site-specific recombination

Explanation of Solution

The recombinase enzyme carries out site-specific recombination between two DNA recognition sites. It is a member of integrase family.