9. Molecular Structure of DNA and RNA Flashcards
an examination of DNA structure and function at the molecular level.
Molecular Genetics
the genetic material. It is a double-stranded structure, with each strand composed of repeating units of deoxyribonucleotides.
Deoxyribonucleic Acid (DNA)
a nucleic acid that is composed of ribonucleotides. In living cells, it is synthesized via the transcription of DNA.
Ribonucleic Acid (RNA)
when a bacterial cell takes up a plasmid vector or segment of chromosomal DNA from the environment;
Transformation
an enzyme that cuts the sugar-phosphate backbone in DNA.
DNase
an enzyme that cuts the sugar-phosphate backbone in RNA.
RNase
an enzyme that digests the polypeptide backbone in a protein.
Protease
a virus that infects bacteria.
Bacteriophage (Phage)
RNA or DNA. A macromolecule that is composed of repeating nucleotide units.
Nucleic Acid
the repeating structural unit of nucleic acids, composed of a sugar, one to three phosphates, and a nitrogen-containing base.
Nucleotide
in DNA or RNA, a long linear polymer formed of nucleotides covalently linked together.
Strand
the arrangement in which two strands of DNA (or sometimes strands of RNA) interact with each other to form a double-stranded helical structure.
Double Helix
the sugar found in DNA.
Deoxyribose
the sugar found in RNA
Ribose
a type of nitrogenous base that has a double-ring structure. Examples are adenine and guanine.
Purines
a type of nitrogenous base that has a single-ring structure. Examples are cytosine, thymine, and uracil.
Pyrimidines
a purine base found in DNA and RNA. It base-pairs with thymine in DNA.
Adenine (A)
a purine base found in DNA and RNA. It base-pairs with cytosine in DNA.
Guanine (G)
a pyrimidine base found in DNA. It base-pairs with adenine in DNA.
Thymine (T)
a pyrimidine base found in DNA and RNA. It base-pairs with guanine in DNA.
Cytosine (C)
a pyrimidine base found in RNA.
Uracil (U)
structure in which a base is attached to a sugar, but no phosphate is attached to the sugar.
Nucleoside
in a DNA or RNA strand, a linkage in which a phosphate group connects two sugar molecules.
Phosphodiester Linkage
the portion of a DNA or RNA strand that is composed of covalently linked phosphates and sugar molecules.
Backbone
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.
Directionality
the observation that in DNA the amounts of A and T are equal, as are the amounts of G and C.
Chargaff’s Rule
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.
Base Pair (bp)
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.
AT/GC Rule
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.
Complementary
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′.
Antiparallel
In DNA, the orientation of base pairs in which the flat sides of the bases are facing each other.
Base Stacking
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.
Grooves
a narrow indentation in the DNA double helix in which the bases have access to water.
Minor Groove
a wide indentation in the DNA double helix in which the bases have access to water.
Major Groove
the predominant form of DNA in living cells. It is a right-handed DNA helix with 10 bp per turn.
B DNA
a left-handed DNA double helix that is found occasionally in living cells.
Z DNA
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.
DNA Methylation
