Chapter 17: Gene Expression: From Gene to Protein Flashcards
Gene Expression
- Process by which information encoded in DNA directs the synthesis of proteins
- In some cases, RNAs that are not translated into proteins are translated and function as RNAs
Transcription
Synthesis of RNA from a DNA template
Messenger RNA (mRNA)
- Type of RNA synthesized from DNA
- Attached to ribosomes in the cytoplasm
- Specifies the primary structure of a protein
Translation
Synthesis of a polypeptide using the genetic information encoded in an mRNA molecule
Primary Transcript
- Initial RNA transcript from any gene
- Also called pre-mRNA when transcribed from a protein-coding gene
Triplet Code
- Genetic information system
- Series of three-nucleotide-long words specifies a sequence of amino acids for a polypeptide chain
Template Strand
DNA strand that provides the pattern/template for ordering by complementary base pairing the sequence of nucleotides in an RNA transcript
Codon
- Three-nucleotide sequence of DNA or mRNA that specifies a particular amino acid or termination signal
- Basic unit of the genetic code
Reading Frame
On an mRNA, the triplet grouping of ribonucleotides used by the translation machinery during polypeptide synthesis
RNA Polymerase
Enzyme that links ribonucleotides into a growing RNA chain during transcription based on complementary binding to nucleotides on a DNA template strand
Promoter
Specific nucleotide sequence in DNA that binds RNA polymerase and indicates where to start transcribing RNA
Transcription Unit
Region of DNA that is transcribed into an RNA molecule
Transcription Initiation Complex
Completed assembly of transcription factors and RNA polymerase bound to a promoter
TATA Box
DNA sequence in eukaryotic promoters crucial in forming the transcription initiation complex
RNA Processing
- Modification of RNA primary transcripts
- Includes:
- Splicing out of introns
- Joining together of exons
- Alteration of the 5’ and 3’ ends
5’ Cap
Modified form of guanine nucleotide added onto the 5’ end of a pre-mRNA molecule
Poly-A Tail
Sequence of 50-250 adenine nucleotides added onto the 3’ end of a pre-mRNA molecule
RNA Splicing
The removal of portions of the transcript (introns) that will not be included in the mRNA and the joining together of the remaining portions (exons) after synthesis of a eukaryotic primary RNA transcript,
Intron
- Non-connecting, intervening sequence within a primary transcript that is removed from the transcript during RNA processing
- Also refers to the region of DNA from which this sequence was transcribed
Exon
- Sequence within a primary transcript
- Remains in the RNA after RNA processing
- Also refers to the region of DNA from which this sequence was transcribed
Spliceosome
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
- RNA molecule
- Functions as an enzyme
- Example= intron that catalyzes its own removal during RNA splicing
Alternative RNA Splicing
- Type of eukaryotic gene regulation at the RNA-processing level in
- Different mRNA molecules are produced from the same primary transcript
- Depends on which RNA segments are treated as exons and which are treated as introns
Domain
Discrete structural and functional region of a protein
Transfer RNA (tRNA)
- RNA molecule that functions as an interpreter between nucleic acid and protein language
- Picks up specific amino acids and recognizes the appropriate codons in the mRNA
Anticodon
- Nucleotide triplet at one end of a tRNA molecule
- Base-pairs with a particular complementary codon on an mRNA molecule
Aminoacyl-tRNA Synthetase
Enzyme that joins each amino acid to the appropriate tRNA
Wobble
- Flexibility in the base-pairing rules
- The nucleotide at the 5’ end of a tRNA anticodon can form hydrogen bonds with more than one kind of base in the third position (3’ end) of a codon
Ribosomal RNA (rRNA)
- RNA molecules
- Together with proteins make up ribosomes
- Most abundant type of RNA
P Site
- One of a ribosome’s three binding sites for tRNA translation
- Holds the tRNA carrying the growing polypeptide chain
A Site
- One of a ribosome’s three binding sites for tRNA during translation
- Holds the tRNA carrying the next amino acid to be added to the polypeptide chain
E Site
- One of a ribosome’s three binding sites for tRNA during translation
- Place where discharged tRNAs leave the ribosome
Silent Mutation
- Nucleotide-pair substitution
- Has no observable effect on the phenotype
- Example= mutation that results in a codon that codes for the same amino acid
Missense Mutation
- Nucleotide-pair substitution
- Results in a codon that codes for a different amino acid
Nonsense Mutation
- Mutation that changes an amino acid codon to one of the three stop codons (UAA, UAG, UGA)
- Results in a shorter and usually nonfunctional protein
Insertion
Mutation involving the addition of one or more nucleotide pairs to a gene
Deletion
Mutational loss of one or more nucleotide pairs from a gene
Frameshift Mutation
- Mutation occuring when nucleotides are inserted or deleted from a gene and the number added or removed is not a multiple of three
- Results in the improper grouping of subsequent nucleotides into codons
Mutagen
Chemical/physical agent that interacts with DNA and causes a mutation
Signal Peptide
- Sequence of about 20 amino acids at or near the leading (amino) end of a polypeptide
- Targets the polypeptide to the endoplasmic reticulum (ER) by binding to a receptor protein on the ER
Signal-Recognition Particle (SRP)
Protein-RNA complex
- Recognizes a signal peptide as it emerges from a ribosome
- Helps direct the ribosome to the endoplasmic reticulum (ER) by binding to a receptor protein on the ER
Polyribosome (Polysome)
Group of several ribosomes attached to and translating the same mRNA molecule
Mutation
Change in the nucleotide sequence of an organism’s DNA or in the DNA or RNA of a virus
Point Mutation
Change in a single nucleotide pair of a gene
Nucleotide-Pair Substitution
- Type of point mutation
- One nucleotide in a DNA strand and its partner in the complementary strand are replaced by another pair of nucleotides
