deoxyribonucleic acid (DNA) - ✔️✔️A polynucleotide that constitutes the genetic material of all cellular
organisms. It is composed of deoxyribonucleotides connected by phosphodiester bonds.
complementary - ✔️✔️Refers to the matching of two strands of DNA or RNA based on the base-pairing
rules.
ribonucleic acid (RNA) - ✔️✔️A polynucleotide composed of ribonucleotides joined by phosphodiester
bonds.
origin of replication - ✔️✔️A site on a chromosome or plasmid where DNA replication is initiated.
replication fork - ✔️✔️The Y-shaped structure where DNA is replicated.
replicon - ✔️✔️A unit of the genome that contains an origin of replication and in which DNA is replicated.
replisome - ✔️✔️A large protein complex that copies the DNA double helix to form two daughter
chromosomes.
DNA polymerase - ✔️✔️An enzyme that synthesizes new DNA using a parental nucleic acid strand (usually
DNA) as a template.
helicases - ✔️✔️Enzymes that use ATP energy to unwind DNA ahead of the replication fork.
topoisomerases - ✔️✔️Enzymes that change the topology of DNA molecules by transiently breaking one
or both strands. They play an important role in DNA replication and transcription.
DNA gyrase - ✔️✔️A topoisomerase enzyme that relieves tension generated by the rapid unwinding of
DNA during DNA replication or transcription.
,primosome - ✔️✔️in bacteria, a complex of proteins that includes the enzyme primase, responsible for
synthesizing the RNA primers needed for DNA replication.
leading strand - ✔️✔️The strand of DNA that is synthesized continuously during DNA replication
lagging strand - ✔️✔️The strand of DNA synthesized discontinuously during DNA replication.
okazaki fragments - ✔️✔️Short stretches of polynucleotides produced during discontinuous DNA
replication.
DNA ligase - ✔️✔️An enzyme that joins two DNA fragments through the formation of a new
phosphodiester bond.
proofreading - ✔️✔️The ability of enzymes to check their products to ensure that the correct product is
made. For instance, DNA polymerase checks newly synthesized DNA and replaces an incorrect
nucleotide with the correct one prior to further synthesis.
catenanes - ✔️✔️Circular, covalently closed nucleic acid molecules that are locked together like the links
of a chain.
origin recognition complex - ✔️✔️A complex of six proteins that "marks" the origins of replication in
eukaryotic chromosomes.
telomeres - ✔️✔️Complexes of DNA and proteins at the ends of eukaryotic chromosomes.
telomerase - ✔️✔️An enzyme in eukaryotes that replicates the ends of chromosomes.
cistron - ✔️✔️A segment of DNA that encodes a single polypeptide.
, gene - ✔️✔️A DNA segment or sequence that codes for a polypeptide, rRNA, or tRNA.
template strand - ✔️✔️A DNA or RNA strand that specifies the base sequence of a new complementary
strand of DNA or RNA.
promoter - ✔️✔️The region on DNA at the start of a gene that RNA polymerase binds to before beginning
transcription.
leader - ✔️✔️A sequence in a gene that lies between the promoter and the start codon. It is transcribed,
becoming a nontranslated sequence at the 5′ end of mRNA. It often aids in initiation and regulation of
transcription and translation.
shine-dalgarno sequence - ✔️✔️A segment in the leader of bacterial mRNA and some archaeal mRNA that
binds to a sequence on the 16S rRNA of the small ribosomal subunit. This helps orient the mRNA on the
ribosome.
coding region - ✔️✔️The portion of a gene from the start codon to the stop codon.
trailer - ✔️✔️That portion of a gene downstream of the coding region. It is transcribed but not translated.
terminator - ✔️✔️A sequence that marks the end of a gene and stops transcription.
transcription - ✔️✔️The process in which RNA with a base sequence complementary to the template
strand of DNA or RNA is synthesized.
transfer RNA - ✔️✔️A small RNA that binds an amino acid and delivers it to the ribosome for
incorporation into a polypeptide chain during protein synthesis.
ribosomal RNA - ✔️✔️The RNA present in ribosomes; contributes to ribosome structure and also directly
involved in the mechanism of protein synthesis.
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