9. Molecular Structure of DNA and RNA

Question 1

an examination of DNA structure and function at the molecular level.

Answer 1

Molecular Genetics

Question 2

the genetic material. It is a double-stranded structure, with each strand composed of repeating units of deoxyribonucleotides.

Answer 2

Deoxyribonucleic Acid (DNA)

Question 3

a nucleic acid that is composed of ribonucleotides. In living cells, it is synthesized via the transcription of DNA.

Answer 3

Ribonucleic Acid (RNA)

Question 4

when a bacterial cell takes up a plasmid vector or segment of chromosomal DNA from the environment;

Answer 4

Transformation

Question 5

an enzyme that cuts the sugar-phosphate backbone in DNA.

Answer 5

DNase

Question 6

an enzyme that cuts the sugar-phosphate backbone in RNA.

Answer 6

RNase

Question 7

an enzyme that digests the polypeptide backbone in a protein.

Answer 7

Protease

Question 8

a virus that infects bacteria.

Answer 8

Bacteriophage (Phage)

Question 9

RNA or DNA. A macromolecule that is composed of repeating nucleotide units.

Answer 9

Nucleic Acid

Question 10

the repeating structural unit of nucleic acids, composed of a sugar, one to three phosphates, and a nitrogen-containing base.

Answer 10

Nucleotide

Question 11

in DNA or RNA, a long linear polymer formed of nucleotides covalently linked together.

Answer 11

Strand

Question 12

the arrangement in which two strands of DNA (or sometimes strands of RNA) interact with each other to form a double-stranded helical structure.

Answer 12

Double Helix

Question 13

the sugar found in DNA.

Answer 13

Deoxyribose

Question 14

the sugar found in RNA

Answer 14

Ribose

Question 15

a type of nitrogenous base that has a double-ring structure. Examples are adenine and guanine.

Answer 15

Purines

Question 16

a type of nitrogenous base that has a single-ring structure. Examples are cytosine, thymine, and uracil.

Answer 16

Pyrimidines

Question 17

a purine base found in DNA and RNA. It base-pairs with thymine in DNA.

Answer 17

Adenine (A)

Question 18

a purine base found in DNA and RNA. It base-pairs with cytosine in DNA.

Answer 18

Guanine (G)

Question 19

a pyrimidine base found in DNA. It base-pairs with adenine in DNA.

Answer 19

Thymine (T)

Question 20

a pyrimidine base found in DNA and RNA. It base-pairs with guanine in DNA.

Answer 20

Cytosine (C)

Question 21

a pyrimidine base found in RNA.

Answer 21

Uracil (U)

Question 22

structure in which a base is attached to a sugar, but no phosphate is attached to the sugar.

Answer 22

Nucleoside

Question 23

in a DNA or RNA strand, a linkage in which a phosphate group connects two sugar molecules.

Answer 23

Phosphodiester Linkage

Question 24

the portion of a DNA or RNA strand that is composed of covalently linked phosphates and sugar molecules.

Answer 24

Backbone

Question 25

in DNA and RNA, refers to the 5′ to 3′ orientation of nucleotides in a strand; in proteins, refers to the linear arrangement of amino acids from the N-terminal to C-terminal ends.

Answer 25

Directionality

Question 26

the observation that in DNA the amounts of A and T are equal, as are the amounts of G and C.

Answer 26

Chargaff's Rule

Question 27

the structure in which two nucleotides in opposite strands of DNA hydrogen bond with each other. For example, an AT base pair is a structure in which an adenine-containing nucleotide in one DNA strand hydrogen bonds with a thymine-containing nucleotide in the complementary strand.

Answer 27

Base Pair (bp)

Question 28

in DNA, the phenomenon in which an adenine base in one strand always hydrogen bonds with a thymine base in the opposite strand, and a guanine always hydrogen bonds with a cytosine.

Answer 28

AT/GC Rule

Question 29

describes sequences in two DNA strands that match each other according to the AT/GC rule. For example, if one strand has the sequence 5′ -ATGGCGGATTT-3′ , then the complementary strand must be 3′ -TACCGCCTAAA-5′ ; in DNA, complementary sequences are also antiparallel.

Answer 29

Complementary

Question 30

refers to an arrangement in a double helix in which one strand is running in the 5′ to 3′ direction, while the other strand runs 3′ to 5′.

Answer 30

Antiparallel

Question 31

In DNA, the orientation of base pairs in which the flat sides of the bases are facing each other.

Answer 31

Base Stacking

Question 32

in DNA, the indentations where the atoms of the bases are in contact with the water in the surrounding cellular fluid. In B DNA, there is a smaller minor groove and a larger major groove.

Answer 32

Grooves

Question 33

a narrow indentation in the DNA double helix in which the bases have access to water.

Answer 33

Minor Groove

Question 34

a wide indentation in the DNA double helix in which the bases have access to water.

Answer 34

Major Groove

Question 35

the predominant form of DNA in living cells. It is a right-handed DNA helix with 10 bp per turn.

Answer 35

B DNA

Question 36

a left-handed DNA double helix that is found occasionally in living cells.

Answer 36

Z DNA

Question 37

Regulatory mechanism in which and enzyme covalently attaches a methyl group (-CH3) to a base in DNA. In Eukaryotes, the base is Cytosine. In Prokaryotes, both Adenine and Cytosine can be methylated.

Answer 37

DNA Methylation