D1.2 Protein Synthesis
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24 Terms
Transcription
The synthesis of pre-mRNA from DNA
Where does transcription occur?
The nucleus
What enzyme is used in transcription?
RNA Polymerase
Promoter Site
The start of the DNA sequence, where RNA polymerase binds to to begin transcription
Role of RNA Polymerase in transcription
RNA polymerase unwinds the DNA strand and moves along the template strand, adding RNA nucleotides to form RNA strand.
What is the template/antisense strand in DNA transcription?
The transcribed DNA strand
What is the coding/sense strand in DNA transcription?
Strand that is not transcribed
What is Gene expression
The process by which information carried by a gene has observable effects on an organism
What is translation
The synthesis of polypeptides from mRNA
Where does translation occur?
In the cytoplasm
What is a codon?
A sequence of 3 nucleotides that correspond to a certain amino acid
Role of mRNA in translation
Contains codons that correspond to an amino acid sequence that codes for a specific polypeptide.
Role of tRNA in translation
Translates the base sequence of mRNA into the amino acid sequence of a polypeptide. Anticodons on one end bind to the mRNA and allow the corresponding amino acid to bind to the other.
What are ribosomes?
Complex structures with large and small subunits for synthesizing polypeptides
Function of ribosome small structure
binding site for mRNA
Function of ribosome large structure
3 binding sites for tRNA: APE
A site of ribosomes
holds tRNA carrying next amino acid to be added to the chain
P site of ribosomes
holds tRNA carrying growing polypeptide
E site of ribosomes
empty/uncharged tRNA leaves ribosome
Degenerate
Different codons can code for the same amino acid
Gene mutation
A change to the base sequence of a gene
What causes sickle cell anemia?
A single base substitution on the beta-globin gene
Post-transcriptional modifications of mRNA
Added methyl cap on the 5’ end and poly-A tails (chain of adenines) on the 3’ end
Spliced out introns (useless sequences)
How does preproinsulin become insulin?
Rough ER: Preproinsulin loses 24 amino acids → proinsulin
Golgi Apparatus: cleaves and packages proinsulin → insulin
