Chapter 14 Flashcards
Gene Expression
The process by which DNA directs protein synthesis, includes two stages: transcription and translation.
Transcription
The synthesis of RNA using information in DNA.
messenger RNA (mRNA)
Produced by transcription.
Translation
The synthesis of a polypeptide, using the information in the mRNA. Can begin before transcription has finished in bacteria. In eukaryotes the nuclear envelope separates transcription from translation.
Ribosomes
The site of translation.
RNA polymerase
An enzyme that pries the DNA strands apart and joins the complementary RNA nucleotides. Can only assemble polynucleotides in the 5’ to 3’ direction.
Promoter
The DNA sequence where RNA polymerase attaches.
Terminator
The sequence signaling the end of transcription in bacteria.
Transcription Unit
The stretch of DNA that is transcribed.
Three stages of transcription
Initiation, Elongation, Termination
RNA splicing
Large portions of the RNA molecule are removed and the remaining portions reconnected. Introns cut out and exons joined together.
Introns
Noncoding regions of the RNA molecule.
Exons
Coding regions of the RNA molecule that are usually translated into amino acid sequences.
Transfer RNA (tRNA)
Translates the mRNA message into protein.
Codons
The mRNA base triplets. Each specifies the amino acid to be placed at the corresponding position along a polypeptide.
Anticodons
tRNA anticodons match with mRNA codons during translation.
Initiation stage of translation
Brings together mRNA, a tRNA with the first amino acid and the two ribosomal subunits.
Mutations
Changes in the genetic material of a cell.
Point mutations
Chemical changes in just one nucleotide pair of a gene. Can lead to the production of an abnormal protein. If it occurs in a gamete, it may be transmitted to the offspring.
Nucleotide-pair substitutions
Replaces one nucleotide and its partner with another pair of nucleotides.
Silent mutations
Have no effect on the amino acid produced by a codon because of the redundancy in the genetic code.
Missense Mutations
Change one amino acid into another.
Nonsense mutations
Change an amino acid codon into a stop codon, nearly always leading to a nonfunctional protein.
Insertion/Deletion
Additions or losses of nucleotide pairs in a gene.
Frameshift Mutation
Produced by the insertion or deletion of nucleotides altering the reading frame of the genetic message.
Mutagens
Physical or chemical agents that cause mutations.
