CHAPTER 10_DNA Structure and Analysis

Question 1

According to the Watson–Crick model, DNA exists in the form of a (right-handed or left-handed?) double helix

Answer 1

right-handed

Question 2

what is the bonding between complementary nitrogenous bases?

Answer 2

Hydrogen bonding

Question 3

For a molecule to serve as the genetic material, it must exhibit four crucial characteristics:

Answer 3

1. replication
2. storage of information
3. expression of information
4. variation by mutation

Question 4

Characteristic of a genetic material that requires the molecule to act as a repository of genetic information that may or may not be expressed by the cell in which it resides

Answer 4

Storage of information

Question 5

transcription of DNA, in which three main types of RNA molecules are synthesized:

Answer 5

1. messenger RNA (mRNA)
2. transfer RNA (tRNA)
3. ribosomal RNA (rRNA)

Question 6

chain of amino acids

Answer 6

polypeptide

Question 7

central dogma of molecular genetics:

Answer 7

“DNA makes RNA, which makes proteins.”

Question 8

a change in the chemical composition of DNA

Answer 8

mutation

Question 9

Levene postulated incorrectly that identical groups of these four components were repeated over and over, which was the basis of his _________

Answer 9

tetranucleotide hypothesis for DNA structure

Question 10

Frederick Griffith, a medical officer in the British Ministry of Health. He performed experiments with several differentstrains of the bacterium __________

Answer 10

Diplococcus pneumoniae.* (now named Streptococcus pneumoniae)

Question 11

what does virulent mean?

Answer 11

infectious

Question 12

what does avirulent mean?

Answer 12

noninfectious

Question 13

virulence depends on the presence of
a polysaccharide capsule; which strain has this capsule, virulent or avirulent?

Answer 13

Virulent

Question 14

Encapsulated bacteria form smooth, shiny surfaced colonies (S) when grown on an agar culture plate; non-encapsulated strains produce rough colonies (R).

Question 15

Each strain of Diplococcus may be one of dozens of different types called ______ that differ in the precise chemical structure of the polysaccharide constituent of the thick, slimy capsule.

Answer 15

serotypes

Question 16

Griffith concluded that the heat-killed IIIS bacteria somehow converted live avirulent IIR cells into virulent IIIS cells. Calling the phenomenon _______, he suggested that the transforming principle might be some part of the polysaccharide capsule or a compound required for capsule synthesis, although the capsule alone did not cause pneumonia.

Answer 16

transformation

Question 17

To use Griffith’s term, the transforming principle from the dead IIIS cells served as a _______— that is, a nutrient source—for the IIR cells.

Answer 17

“pabulum”

Question 18

chemical name then used to describe DNA

Answer 18

“sodium desoxyribonucleate”

Question 19

Further testing clearly established that the transforming principle was ____

Answer 19

DNA

Question 20

In a reasonably short time, many new phages are constructed and the bacterial cell is lysed, releasing the progeny viruses. This process is referred to as the _____

Answer 20

lytic cycle

Question 21

Because DNA contains phosphorus (P) but not sulfur, 32P effectively labels DNA; because proteins contain sulfur (S) but not phosphorus, 35S labels protein.

Question 22

if E. coli is treated with the enzyme lysozyme, the outer wall of the cell can be removed without destroying the bacterium. Enzymatically treated cells are naked, so to speak, and contain only the cell membrane as their outer boundary. Such structures are called ________

Answer 22

protoplasts (or spheroplasts)

Question 23

When added to E. coli protoplasts, the purified DNA resulted in the production of complete fX174 bacteriophages. This process of infection by only the viral nucleic acid, called _______

Answer 23

transfection

Question 24

Indirect evidences that supports the concept that DNA is the genetic material in eukaryotes

Answer 24

1. Distribution of DNA (Diploid; haploid)
2. Mutagenesis

Question 25

The molecule serving as the genetic material is expected to absorb at the wavelength(s) found to be mutagenic.

Question 26

UV light is most mutagenic at the wavelength of _______, and both DNA and RNA absorb UV light most strongly at ------ nm. On the other hand, protein absorbs most strongly at _______, yet no significant mutagenic effects are observed at that wavelength.

Answer 26

260 nanometers (nm) 280 nm

Question 27

Direct evidence that supports the concept that DNA is the genetic material in eukaryotes

Answer 27

Recombinant DNA studies

Question 28

involves splicing together DNA sequences from different organisms

Answer 28

recombinant DNA technology

Question 29

can provide the full set of DNA sequences of organisms

Answer 29

Genomics

Question 30

Their RNA serves as a template for the synthesis of the complementary DNA molecule

Answer 30

Retroviruses

Question 31

The process, _______, occurs under the direction of an RNA-dependent DNA polymerase enzyme called _________

Answer 31

reverse transcription reverse transcriptase

Question 32

Building blocks of nucleic acids

Answer 32

Nucleotides (sometimes called mononucleotides)

Question 33

3 essential components of a nucleotide:

Answer 33

1. nitrogenous base 2. pentose sugar (a 5-carbon sugar) 3. phosphate group

Question 34

two kinds of nitrogenous bases:

Answer 34

1. nine-member double-ring purines and the 2. six-member single-ring pyrimidines.

Question 35

The two purines are...

Answer 35

Adenine Guanine

Question 36

Some viruses contain an RNA core rather than a DNA core. In these viruses, it appears that RNA serves as the genetic material—an exception to the general rule that DNA performs this function

Answer 36

tobacco mosaic virus (TMV)

Question 37

_______ is a molecule composed of a purine or pyrimidine base and a ribose or deoxyribose sugar. If a phosphate group is added to the nucleoside, the molecule is now called a ______

Answer 37

nucleoside nucleotide

Question 38

_______ are important in cell bioenergetics because of the large amount of energy involved in adding or removing the terminal phosphate group.

Answer 38

adenosine triphosphate (ATP) and guanosine triphosphate (GTP)

Question 39

The linkage between two mononucleotides consists of a phosphate group linked to two sugars. It is called...

Answer 39

phosphodiester bond

Question 40

–includes alterations of chromosome number and rearrangements within and between chromosomes –provides the raw material for the process of evolution

Answer 40

Genetic Variation

Question 41

Hershey and Chase knew from existing data that: 1. T2 phages consist of approximately 50 percent protein and 50 percent DNA 2. Infection is initiated by adsorption of the phage by its tail fibers to the bacterial cell. 3. The production of new viruses occurs within the bacterial cell.

Question 42

* process of infection by only the viral nucleic acid

Answer 42

transfection

Question 43

Short chains consisting of up to approximately 30 nucleotides linked together are called ________; longer chains are called _______

Answer 43

oligonucleotides polynucleotides

Question 44

The data available to Watson and Crick, crucial to the development of their proposal, came primarily from two sources:

Answer 44

(1) base composition analysis of hydrolyzed samples of DNA (2) X-ray diffraction studies of DNA.

Question 45

X rays scatter (diffract) in a pattern that depends on the molecule’s atomic structure. The pattern of diffraction can be captured as spots on photographic film and analyzed for clues to the overall shape of and regularities within the molecule. This process is called...

Answer 45

X-ray diffraction analysis

Question 46

Major features of the double helix model by Watson and Crick:

Answer 46

1. Two long polynucleotide chains are coiled around a central axis, forming a right-handed double helix. 2. The two chains are antiparallel; that is, their C-5′ to C-3′ orientations run in opposite directions. 3. The bases of both chains are flat structures lying perpendicular to the axis; they are “stacked” on one another, 4. The nitrogenous bases of opposite chains are paired as the result of the formation of hydrogen bonds 5. Each complete turn of the helix is 34 Å (3.4 nm) long; thus, each turn of the helix is the length of a series of 10 base pairs. 6. A larger major groove alternating with a smaller minor groove winds along the length of the molecule. 7. The double helix has a diameter of 20 Å (2.0 nm).

Question 47

alternative form of DNA ______ does exist as a left-handed helix

Answer 47

(Z-DNA)

Question 48

The specific A-T and C-G base pairing is described as _______ and results from the chemical affinity that produces the hydrogen bonds in each pair of bases.

Answer 48

complementarity

Question 49

why is purine-purine and pyrimidine-pyrimidine discounted by Watson and Crick?

Answer 49

Such pairings would lead to aberrant diameters of, in one case, more than and, in the other case, less than 20 Å because of the respective sizes of the purine and pyrimidine rings. In addition, the three-dimensional configurations that would be formed by such pairings would not produce an alignment that allows sufficient hydrogen-bond formation.

Question 50

a very weak electrostatic attraction between a covalently bonded hydrogen atom and an atom with an unshared electron pair.

Answer 50

hydrogen bond The hydrogen atom assumes a partial positive charge, while the unshared electron pair—characteristic of covalently bonded oxygen and nitrogen atoms—assumes a partial negative charge.

Question 51

the hydrophobic nitrogenous bases are stacked almost horizontally on the interior of the axis and are thus shielded from the watery environment that surrounds the molecule within the cell. The hydrophilic sugar-phosphate backbones are on the outside of the axis, where both components may interact with water. These molecular arrangements provide significant chemical stabilization to the helix.

Question 52

other form of DNA right-handed helices that have been discovered and is found under even greater dehydration conditions than those observed during the isolation of A- and B-DNA

Answer 52

C-DNA

Question 53

other form of DNA right-handed helices that have been discovered and occur in helices lacking guanine in their base composition

Answer 53

D-DNA and E-DNA

Question 54

other form of DNA right-handed helices that have been discovered that if DNA is artificially stretched, still another conformation is assumed, called...

Answer 54

P-DNA (named for Linus Pauling)

Question 55

when a small synthetic DNA oligonucleotide containing only G-C base pairs was studied. ______ takes on the rather remarkable configuration of a left-handed double helix.

Answer 55

Z-DNA

Question 56

estimate of the periodicity of nitrogenous bases =

Answer 56

3.4 Angstroms apart

Question 57

strong arcs on periphery of an X-ray diffraction of DNA means that

Answer 57

- closely spaced aspects of the molecule

Question 58

form of DNA right-handed helices where the base pairs are perpendicular to the helix

Answer 58

B-DNA

Question 59

form of DNA right-handed helices where they are tilted and pulled away from the helix

Answer 59

A-DNA

Question 60

RNAs are distinguished according to their sedimentation behavior in a centrifugal field and by their size (the number of nucleotides each contains).

Question 61

Sedimentation behavior depends on a molecule’s density, mass, and shape, and its measure is called the _______

Answer 61

Svedberg coefficient (S)

Question 62

The molecule with a melting point (Tm) of 83 degree Celcius has a greater triple-bond GC content than the molecule with a Tm equal to 77 degree Celcius

Question 63

The red fluorescence is produced by ________ counterstaining of chromosomal DNA

Answer 63

propidium iodide

Question 64

a unit of measurement for the rate at which a particle sediments in a centrifuge

Answer 64

Svedberg coefficient (S)

Question 65

function as nonspecific workbenches where proteins are synthesized during translation

Answer 65

Ribosomes

Question 66

During unwinding, the viscosity of DNA decreases and UV absorption increases (called the _____).

Answer 66

hyperchromic shift

Question 67

The molecule with a higher Tm has a higher percentage of G-C base pairs than A-T base pairs since G-C pairs share three hydrogen bonds compared to the two bonds between A-T pairs

Question 68

The denaturation/renaturation of nucleic acids is the basis for one of the most useful techniques in molecular genetics—_____________

Answer 68

molecular hybridization

Question 69

Because fluorescence is used, the technique is known by the acronym FISH ________.

Answer 69

fluorescent in situ hybridization

Question 70

This technique may be adapted to separate different-sized fragments of DNA and RNA chains

Answer 70

electrophoresis

Question 71

What do you call the bond between nitrogenous base and sugar

Answer 71

Glycosidic bond