ch 9 molecular structure of dna & rna Flashcards
molecular genetics
an examination of dna structure and function at the molecular level
dna (deoxyribonucleic acid)
the genetic material; double stranded structure with repeating units of deoxyribonucleotides
rna (ribonucleic acid)
a nucleic acid that is composed of ribonucleotides; in living cells, rna is synthesized via the transcription of dna
transformation
- when a bacterial cell takes up a plasmid vector or segment of chromosomal dna from the environment
- when a normal cell is converted into a malignant cell
DNase
an enzyme that cuts the sugar phosphate backbone in dna
RNase
an enzyme that cuts the sugar phospate backbone in RNA
protease
an enzyme that digests the polypeptide backbone in a protein
bacteriophage (phage)
a virus that infects bacteria
nucleic acid
rna or dna; macromolecule that is composed of repeating nucleotide units
nucleotide
the repeating structural unit of nucleic acid, composed of a sugar, one to three phosphates, and a nitrogen-containing base
strand
in dna or rna, a long linear polymer formed of nucleotides covalently linked together
double helix
the arrangement in which two strands of dna (or sometimes stands of rna) interact with each other to form a double stranded helical structure
deoxyribose
the sugar found in dna
ribose
the sugar found rna
purine
a type of nitrogenous base that has a double ring structure; examples are adenine and guanine
pyrimidine
a type of nitrogenous base that has a single ring structure; examples are cytosine, thymine, and uracil
adenine (A)
a purine base found in dna and rna; base pairs w thymine in dna
guanine (G)
a purine base found in dna and rna; base-pairs with cytosine in dna
thymine (T)
a pyrimidine base found in dna; base pairs with adenine in dna
cytosine (C)
a pyrimidine base found in dna and rna; base pairs with guanine
uracil (U)
a pyrimidine base found in rna
nucleoside
structure in which a base is attached to a sugar but no phosphate is attached to the sugar
phosphodiester linkage
in dna or rna stand, a linkage in which a phosphate group connects two sugar molecules
backbone
the portion of a dna or rna strand that is composed of covalently linked phosphate and sugar molecules
directionality
in dna & 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
chargaff’s rule
observation that in dna, amount of A and T are equal and amounts of G and C are equal
base pair (bp)
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 stand hydrogen bonds with a thymine-containing nucleotide in the complementary strand
at/gc rule
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 hydrigen bonds with a cytosine
complementary
describes sequences in which two dna strands that match each other accordign to the at/gc rule; antiparallel
antiparallel
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’
base stacking
in dna, the orientation of base pairs in which the flat sides of the bases are facing each other
grooves
in dna, the indentations where the atoms of the bases are in contact with the water in surrounding cellular fluid; in B dna, there is a minor groove and major groove
minor groove
a narrow indentation in the dna double helix in which the bases have access to water
major groove
a wide indentation in the dna double helix in which the bases have access to water
B dna
the predominant form of dna in living cells; right handed dna helix with 10 bp per turn
Z dna
a left handed dna double helix that is found occasionally in living cells
dna methylation
a regulatory mechanism in which an 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
