bio - evolution chap. 15

Gene expression

process by which DNA directs the synthesis of proteins or RNA (one gene - one RNA)

Central dogma

DNA → RNA → Protein

replication

the copying of DNA to make more DNA before cell division

transcription

the decoding of DNA to make a strand of RNA

translation

using a strand of mRNA to make a polypeptide/protein

pre-mRNA

what is produced from the DNA in eukaryotes (un-edited)

mRNA

edited version that can leave the nucleus and carry the code from DNA to the ribosome (message)

tRNA

carries amino acids from the cytoplasm to the ribosome during translation (interpreter)

rRNA

60% of the ribosome and is the site of protein synthesis

transcription steps 

1. initiation

2. elongation

3. termination   

redundancy

1+ codon code for an amino acid

TATA box

helps establish the initiation site for RNA polymerase, where the transcription factors bind

where does transcription occur

nucleus

RNA processing 

adds a 5’ cap (at the start) and a poly A tail at the end) and splices out the introns 

RNA splicing

Introns (non coding) are cut out and exons (codes for amino acids) are joined together

Alternative splicing 

produce different combinations of exons - more than 1 protein from 1 mRNA strand 

spliceosomes

catalyze the process of removing introns and joining exons (do the splicing) 

anticodon

three-nucleotide sequence in a tRNA molecule complementary to an mRNA codon

the start codon 

AUG 

where does translation take place

Ribosome

A site 

holds amino acids 

P site 

holds peptide chain 

E site

Exit site for tRNA

gene expression in prokaryotes 

occurs in cytoplasm, no pre-mRNA, no introns

name of the protein that helps other proteins fold  

chaperonin