Chapter 8

Colinearity

Linear order of nucleotides in a gene determines the linear order of amino acids in a polypeptide

Transcription

Initiation, Elongation, and Termination

Three major types of RNA

Ribosomal RNA, Transfer RNA, Messenger RNA

RNA polymerase 1

transcribes ribosomal RNA

RNA polymerase 2

All protein-coding genes

tRNA

transfers free amino acids to the mRNA ribosome complex

rRNA

primary structural and functional component of ribosomes

mRNA

precursor of proteins, carries genetic instructions from DNA

Splicing

Non-coding sequences are removed from pre-mRNA and coding sequences are joined together to form mRNA

Mitochondria organelles

No spliceosome

Introns code for proteins that participate in their own removal

Introns

Increase transcription frequency and efficiency, can encode for microRNAs and small nucleolar RNAs

Spliceosomes

small nuclear ribonucleoprotein

Polypeptides

Linear polymers of amino acids

Protein Domains

Regions that can fold in upon themselves to acquire well-defined structures

Ribosomes

particles where protein synthesis takes place

Aminoacyl-tRNA synthases

Catalyze the formation of an aminoacyl bond between amino acids and the CCA stems of tRNA

Initiation

Rate-limiting step of protein synthesis where the ribosome, mRNA, and initiator tRNA assemble to start translation

Elongation

The second stage of protein synthesis where the ribosome extends a nascent polypeptide chain along amino acid

Termination

Triggered when a ribosome encounters a stop codon in the mRNA’s A site

Four determining factors of protein structure

1. Amino Acid Sequence

2. alpha helices and beta sheets

3. disulfide bridges between cysteines

4. assembly of subunits

Polycistronic mRNA

Encodes several proteins

characteristic of many bacterial and chloroplast mRNAs

Monocistronic mRNA

Encodes only one protein, ALL eukaryotic mRNAs are monocistronic

Base-pair substitution

Replaces one nucleotide and its partner with another pair of nucleotides