The simplest definition of a gene is

“a unit of DNA that contains the information to specify synthesis of a single poly- peptide chain or functional RNA (such as a tRNA).”

bases in the template DNA strand base-pair with complementary incoming rNTPs, which are then joined in a polymerization reaction catalyzed by

RNA polymerase

the site on the DNA template at which RNA polymerase begins transcription is numbered

+1

RNA has uracil in place of

RNA poly- merase, with the help of initiation factors (discussed later), recognizes and binds to a specific sequence of double- stranded DNA called a

where cataly- sis of phosphodiester bond formation between rNTPs that are complementary to the template strand takes place

active site

The 12–14-base-pair region of melted DNA in the polymerase is known as the

Transcription initiation is considered complete when

RNA polymerase moves along the template DNA, opening the double-stranded DNA in front of its direction of movement and guiding the strands back together so that they reassociate at the upstream end of the transcription bubble

the growing RNA chain is called the 

comprising RNA polymerase, template DNA, and the nascent RNA strand, is extraordinarily sta- ble

elongation complex

the final stage in RNA synthesis, the completed RNA molecule is released from the RNA polymerase and the polymerase dissociates from the template DNA

two related large subunits (β′ and β), two copies of a smaller subunit (α), and one copy of a fifth subunit (ω) that is not essential for transcription or cell viability, but that stabilizes the enzyme and assists in the assembly of its subunits

Such an arrangement of genes in a functional group is called an

Each section of the mRNA represents the unit (or gene) that encodes one of the proteins in the series. This arrangement results in the

In eukaryotic cells, however, the site of RNA synthesis—the nucleus—is separated from the site of translation—the cytoplasm. Furthermore, the primary transcripts of protein-coding genes are

protects an mRNA from enzymatic degradation and assists in its export to the cytoplasm. ______  is also bound by a protein factor required to begin trans- lation in the cytoplasm.

is part of a complex of proteins that can locate and cleave a transcript at a specific site and then add the correct number of A residues, in a process that does not require a template.

the internal cleav- age of a transcript to excise the introns and stitch together the coding exons

The functional eukaryotic mRNAs produced by RNA processing retain noncoding regions, referred to as

The pres- ence of multiple introns in many eukaryotic genes permits expression of multiple, related proteins from a single gene by means of

In higher eukaryotes, alter- native splicing is an important mechanism for production of different forms of a protein, called

sets of three-nucleotide sequences

carries the genetic informa- tion transcribed from DNA in a linear form.

the key to deciphering the codons in mRNA

Each type of amino acid has its own subset of tRNAs, which are covalently bound to that amino acid and carry it to the growing end of a polypeptide chain when the next codon in the mRNA calls for it. The correct tRNA with its attached amino acid is selected at each step because each specific tRNA molecule contains a three- nucleotide sequence, an

These complex structures, which physically move along an mRNA molecule, catalyze the assembly of amino acids into polypeptide chains.

Translation, or decoding, of the four-nucleotide language of DNA and mRNA into the twenty–amino acid language of proteins requires both tRNAs and enzymes called

To participate in protein syn- thesis, a tRNA molecule must become chemically linked to a particular amino acid via a high-energy bond, forming an

tRNAs, the 3′ end of the unlooped

wobble position: that is, the ________ base in an mRNA codon and the corresponding -__________ base in its tRNA anticodon.

Each of the 20 different syn- thetases recognizes one amino acid and all its compatible, or _______, tRNAs.

Like transcription, the complex process of translation can be divided into three stages

The small ribosomal subunit contains a single rRNA molecule, referred to as

The large subunit contains a molecule of _______ and one molecule of 5S rRNA, plus an additional molecule of 5.8S rRNA in verte- brates.