Chapter 17: From Gene to Protein Flashcards
Gene expression
The process by which DNA directs protein synthesis including two stages; transcription and translation
Garrod
First suggested that genes dictate phenotypes through enzymes that catalyze specific chemical reactions
Beadle and Tatum
Breaded bread mold to create the “one gene - one enzyme hypothesis”
One gene - one polypeptide hypothesis
The function of a gene is to dictate production of a specific polypeptide
Transcription
Synthesis of RNA using information in DNA
Messenger RNA (mRNA)
Carries the instructions for protein synthesis from the nucleus to the ribosome
Translation
Synthesis of a polypeptide, using information in the mRNA
Triple code
Series of nonoverlapping, three-nucleotides “words”
Template strand
One of two strands that provides a template for ordering the sequence of complementary nucleotides in an RNA transcript
Codon
mRNA base triplet
Reading frame
Correct grouping that codons must be read in in order for the specified polypeptide to be produced
RNA polymerase
Pries the DNA strands apart and joins together the RNA nucleotides
Promoter
The DNA sequence where RNA polymerase attaches to
Terminator
The sequence signaling the end of transcription
Transcription unit
The stretch of DNA that is transcribed
Transcription factors
Help guide the binding of RNA polymerase and the initiation of transcription
Transcription initiation complex
The completed assembly of transcription factors and RNA polymerase II bound to a promoter
TATA box
A promoter crucial in forming the initiation complex
RNA processing
Enzymes in the eukaryotic nucleus modify pre-mRNA before the genetic messages are passed into the cytoplasm
5’ cap
Modified nucleotide added to the 5’ end
poly-A tail
Modification added to the 3’ end
RNA splicing
The removal of non coding stretches of nucleotides between coding regions
Introns
Noncoding segments in genes, also called intervening sequences
Exons
The regions not considered introns that eventually get expressed, usually translated into amino acid sequences
stop codons
UAA, UAG, UGA
Start codon
AUG, codes for Methionine
Alternative RNA splicing
Genes that can encode more than one kind of polypeptide, depending on which segments are treated as exons during splicing
Translation
Using mRNA to build a polypeptide
Anticodon
End of an RNA strand that base pairs with a complementary codon on mRNA
Wobble
Flexible pairing at the third base of a codon that allows some tRNAs to bind to more than one codon
P site
Holds the tRNA that carries the growing polypeptide chain
A site
Arrival site, holds the tRNA that carries the next amino acid to be added to the chain
E site
Exit site, where discharged tRNAs leave the ribosome
Three stages of translation
Initiation, elongation, termination
Polyribosome
Enables a cell to make copies of a polypeptide very quickly
Mutations
Changes in the genetic information of a cell, change in the nucleotide sequence of an organisms DNA
Point mutation
Change in a single nucleotide pair of a gene
Nucleotide pair substitution
Replaces one nucleotide and its partner with another pair of nucleotides. Silent - no effect, missense- code for incorrect amino acid, nonsense - change codon into stop codon
Insertions and deletions
Additions or losses or nucleotide pairs in a gene
Frameshift mutations
Whenever the number of nucleotides inserted or deleted is not a multiple of three
Spontaneous mutations
Errors during DNA replication or recombination
Mutagens
Physical and chemical agents that interact with DNA in ways that cause mutations
Gene
A region of DNA that can be expressed to produce a final functional product that is either a polypeptide or an RNA molecule
