BSC2010 - Chapter 12 Vocabulary

gene expression

The process by which information encoded in DNA directs the synthesis of proteins or, in some cases, RNAs that are not translated into proteins and instead function as RNAs.

protein-coding genes

Genes that encode instructions for making proteins.

non-protein coding genes

genes that code for RNA that do not get translated into proteins

transcription

synthesis of an RNA molecule from a DNA template

mRNA

messenger RNA; type of RNA that carries instructions from DNA in the nucleus to the ribosome

translation

Process by which mRNA is decoded and a protein is produced

central dogma

DNA -> RNA -> Protein

RNA modification

A step in the processes of creating a mature mRNA in which 5' caps and poly-A tails are added, and introns are spliced out and exons are joined together.

pre-mRNA

precursor mRNA; the first strand of mRNA produced by gene transcription that contains both introns and exons

Transfer RNA (tRNA)

An RNA molecule that functions as an interpreter between nucleic acid and protein language by picking up specific amino acids and recognizing the appropriate codons in the mRNA

Ribosomal RNA (rRNA)

type of RNA that makes up the major part of ribosomes

promoter

specific region of a gene where RNA polymerase can bind and begin transcription

terminator

A special sequence of nucleotides in DNA that marks the end of a gene. It signals RNA polymerase to release the newly made RNA molecule, which then departs from the gene

regulatory sequences

sections of DNA that are involved in controlling the activity of genes

initiation of transcription

RNA polymerase attaches to the promoter region on the DNA and begins to unzip the DNA into two strands.

sigma factor

a protein that associates with RNA polymerase that facilitates its binding to specific promoters

RNA Polymerase

enzyme that links together the growing chain of RNA nucleotides during transcription using a DNA strand as a template

open complex

the region of separation of two DNA strands produced by RNA polymerase during transcription

elongation (transcription)

RNA polymerase traverses the template strand and uses base pairing complementarity with the DNA template to create an RNA copy

template strand

The DNA strand that provides the template for ordering the sequence of nucleotides in an mRNA transcript.

coding strand

the strand of DNA that is not used for transcription and is identical in sequence to mRNA, except it contains uracil instead of thymine

termination of transcription

The third, and last, phase of transcription in which the mRNA transcript is released when RNA polymerase reaches the terminator sequence

transcription factors

Collection of proteins that mediate the binding of RNA polymerase and the initiation of transcription.

preinitiation complex

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

mature RNA

Eukaryotic RNA that has been spliced and processed and is ready for translation

5' cap

The 5' end of a pre-mRNA molecule modified by the addition of a cap of guanine nucleotide.

poly A tail

Modified end of the 3' end of an mRNA molecule consisting of the addition of some 50 to 250 adenine nucleotides.

introns

A noncoding, intervening sequence within a eukaryotic gene.

exons

Coding segments of eukaryotic DNA.

splicing

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

spliceosome

A large complex made up of proteins and RNA molecules that splices RNA by interacting with the ends of an RNA intron, releasing the intron and joining the two adjacent exons.

ribozyme

a type of RNA that can act as an enzyme

genetic code

collection of codons of mRNA, each of which directs the incorporation of a particular amino acid into a protein during protein synthesis

codons

The three-base sequence of nucleotides in mRNA

start codon

AUG; codes for the amino acid methionine

stop codons

UAA, UAG, UGA

reading frame

The way a cell's mRNA-translating machinery groups the mRNA nucleotides into codons

anticodon

group of three bases on a tRNA molecule that are complementary to an mRNA codon

N-terminus

the end of a polypeptide or protein that has a free amino group

C-terminus

the end of a polypeptide or protein that has a free carboxyl group

peptide bonds

Bonds between amino acids

aminoacyl-tRNA synthetase

An enzyme that joins each amino acid to the correct tRNA.

charged tRNA

A transfer RNA molecule with an amino acid attached to its 3' end.

ribosome

site of protein synthesis

peptidyl site (P site)

The site on the ribosome where amino acids are joined by a peptide bond.

aminoacyl site (A site)

binds a new tRNA molecule containing an amino acid to be added to the growing polypeptide chain

exit site (E site)

a site on the ribosome from which an uncharged tRNA exits

initiation of translation

brings together mRNA, a tRNA with the first amino acid, and the two ribosomal subunits

initiation factors

proteins that bring in the large subunit that completes the translation initiation complex

elongation (translation)

codon recognition, peptide bond formation, translocation

elongation factors

Proteins involved in the elongation phase of translation, assisting ribosomes in the synthesis of the growing peptide chain.

peptidyl transfer reaction

During translation, the transfer of the polypeptide from the tRNA in the P site to the amino acid at the A site.

polyribosome (polysome)

A group of several ribosomes attached to, and translating, the same messenger RNA molecule.

release factor

the protein that binds to the stop codon during termination of translation

termination of translation

occurs when a stop codon in the mRNA reaches the A site of the ribosome