7-methylguanosine cap modification added to the 5′ end of pre-mRNAs to protect mRNA from degradation and assist translation

aminoacyl tRNA synthetase enzyme that “charges” tRNA molecules by catalyzing a bond between the tRNA and a corresponding amino acid

anticodon three-nucleotide sequence in a tRNA molecule that corresponds to an mRNA codon

CAAT box (GGCCAATCT) essential eukaryotic promoter sequence involved in binding transcription factors

Central Dogma states that genes specify the sequence of mRNAs, which in turn specify the sequence of proteins

codon three consecutive nucleotides in mRNA that specify the insertion of an amino acid or the release of a polypeptide chain during translation

colinear in terms of RNA and protein, three “units” of RNA (nucleotides) specify one “unit” of protein (amino acid) in a consecutive fashion

degeneracy (of the genetic code) describes that a given amino acid can be encoded by more than one nucleotide triplet; the code is degenerate, but not ambiguous

electrophoresis technique used to separate DNA fragments according to size

exon sequence present in protein-coding mRNA after completion of pre-mRNA splicing

FACT complex that “facilitates chromatin transcription” by disassembling nucleosomes ahead of a transcribing RNA polymerase II and reassembling them after the polymerase passes by

GC-rich box (GGCG) nonessential eukaryotic promoter sequence that binds cellular factors to increase the efficiency of transcription; may be present several times in a promoter

helicase during replication, this enzyme helps to open up the DNA helix by breaking the hydrogen bonds

induced mutation mutation that results from exposure to chemicals or environmental agents

initiator tRNA in prokaryotes, called tRNAMet ; in eukaryotes, called tRNAi; a tRNA that interacts with a start codon, binds directly to the ribosome P site, and links to a special methionine to begin a polypeptide chain

intron non–protein-coding intervening sequences that are spliced from mRNA during processing

Kozak’s rules determines the correct initiation AUG in a eukaryotic mRNA; the following consensus sequence must appear around the AUG: 5’-GCC(purine)CCAUGG-3’; the bolded bases are most important

lagging strand during replication, the strand that is replicated in short fragments and away from the replication fork

leading strand strand that is synthesized continuously in the 5′-3′ direction which is synthesized in the direction of the replication fork

ligase enzyme that catalyzes the formation of a phosphodiester linkage between the 3′ OH and 5′ phosphate ends of the DNA

mismatch repair type of repair mechanism in which mismatched bases are removed after replication

mutation variation in the nucleotide sequence of a genome

nonsense codon one of the three mRNA codons that specifies termination of translation

nucleotide excision repair type of DNA repair mechanism in which the wrong base, along with a few nucleotides upstream or downstream, are removed

Octamer box (ATTTGCAT) nonessential eukaryotic promoter sequence that binds cellular factors to increase the efficiency of transcription; may be present several times in a promoter

Okazaki fragment DNA fragment that is synthesized in short stretches on the lagging strand

peptidyl transferase RNA-based enzyme that is integrated into the 50S ribosomal subunit and catalyzes the formation of peptide bonds

point mutation mutation that affects a single base

poly-A tail modification added to the 3′ end of pre-mRNAs to protect mRNA from degradation and assist mRNA export from the nucleus

polysome mRNA molecule simultaneously being translated by many ribosomes all going in the same direction

preinitiation complex cluster of transcription factors and other proteins that recruit RNA polymerase II for transcription of a DNA template

primase enzyme that synthesizes the RNA primer; the primer is needed for DNA pol to start synthesis of a new DNA strand

primer short stretch of nucleotides that is required to initiate replication; in the case of replication, the primer has RNA nucleotides

proofreading function of DNA pol in which it reads the newly added base before adding the next one

reading frame sequence of triplet codons in mRNA that specify a particular protein; a ribosome shift of one or two nucleotides in either direction completely abolishes synthesis of that protein

replication fork Y-shaped structure formed during initiation of replication

RNA editing direct alteration of one or more nucleotides in an mRNA that has already been synthesized

Shine-Dalgarno sequence (AGGAGG); initiates prokaryotic translation by interacting with rRNA molecules comprising the 30S ribosome

signal sequence short tail of amino acids that directs a protein to a specific cellular compartment

silent mutation mutation that is not expressed

single-strand binding protein during replication, protein that binds to the single-stranded DNA; this helps in keeping the two strands of DNA apart so that they may serve as templates

sliding clamp ring-shaped protein that holds the DNA pol on the DNA strand

small nuclear RNA molecules synthesized by RNA polymerase III that have a variety of functions, including splicing pre-mRNAs and regulating transcription factors

splicing process of removing introns and reconnecting exons in a pre-mRNA

spontaneous mutation mutation that takes place in the cells as a result of chemical reactions taking place naturally without exposure to any external agent

start codon AUG (or rarely, GUG) on an mRNA from which translation begins; always specifies methionine

telomerase enzyme that contains a catalytic part and an inbuilt RNA template; it functions to maintain telomeres at chromosome ends

telomere DNA at the end of linear chromosomes

topoisomerase enzyme that causes underwinding or overwinding of DNA when DNA replication is taking place

transformation process in which external DNA is taken up by a cell

transition substitution when a purine is replaced with a purine or a pyrimidine is replaced with another pyrimidine

transversion substitution when a purine is replaced by a pyrimidine or a pyrimidine is replaced by a purine