BIO Chapter 17

• each gene dictates production of a specific polypeptide
• ex: gene A codes for polypeptide A and variations because of different alleles

transfer from nucleic acid language (DNA) to protein language

• synthesis of RNA under direction of DNA
• produces messenger RNA (mRNA)
• takes place in the nucleus

• synthesis of a polypeptide (protein)
• occurs on ribosomes

Cells are governed by a cellular chain of command: DNA --> RNA --> protein

• 4 nucleotide bases in DNA
• 20 amino acids
• Codons are 3 bases, read in 5' to 3' direction (each codon specifies amino acid)

• No ambiguity within the genetic code - means each codon only appears once (and codes for a specific amino acid)
• There is redundancy in the genetic code. For most proteins, there are multiple codons.

pries DNA strands apart and hooks together RNA nucleotides

• Initiation
• Elongation
• Termination

• brings everything together and is now ready to start transcription
• needs to have promoter region including TATA to start

• RNA polymerase moves along the DNA and untwists the double helix
• happens very quickly
• through elongations, we get growing mRNA strand

• In bacteria, polymerase stops transcription at the end of the terminator
• In eukaryotes, polymerase continues transcription after the pre-mRNA is cleaved from the growing RNA chain; the polymerase eventually falls off the DNA

• The 5' end receives a modified nucleotide 5' cap
• The 3' end gets a poly-A tail
• Cap and tail helps make it easier to get out of nucleus, helps attaching, and protects mRNA

• intervening sequences; noncoding regions
• don't need introns in translation

• other regions; eventually expessed
• usually translated into amino acid sequences

removes introns and joins exons, creating an mRNA molecule with a continuous coding sequence

• helps translate an mRNA message into protein
• one end of tRNA has anticodon, and the other end has an amino acid. Anticodon matches up with the mRNA codon
• *serves as adaptor molecule in protein synthesis; translates mRNA codons into amino acids

Ribosomes facilitate specific coupling of tRNA anticodons with mRNA codons in protein synthesis

• along with proteins, make up the two ribosomal subunits
• plays catalytic (ribozyme) roles and structural roles in ribosomes

• Initiation
• Elongation
• Termination

Brings together mRNA, a tRNA with the first amino acid, and the two ribosomal subunits

• 3 steps:
• Codon recognition
• Peptide bond formation
• Translocation

occurs when anticodons on tRNA recognize codons on mRNA

when we transfer amino acids from tRNA onto the elongated chain of amino acids

everything moves down a spot

• Occurs when stop codon in mRNA reaches 'A site' of ribosome
• our bodies need to regulate so we don't have too much or too few proteins

• Polypeptide chains are modified after translation
• Completed proteins are targeted to specific sites in the cell

• changes in genetic material of a cell or virus
• not always bad - forms natural selection

changes in just one base pair of a gene

• Base-pair substitutions
• Base-pair insertions or deletions

What we read

when each codon is changed and frame is shifted; causes nonsense and missense from insertions or deletions

aka neutral mutation because it doesn't affect the actual outcome of protein structure or function

new codon codes for an amino acid, just not the right amino acid (doesn't make sense)

base pair codes for a stop codon; don't get an amino acid

no frameshift occurs, but one amino acid is missing

• physical or chemical agent that can cause mutations
• different than carcinogen because not all mutagens have to do with cancer.

Carries info specifying amino acid sequences of proteins from DNA to ribosomes

Is a precursor to mRNA, rRNA, or tRNA, before being processed. Some intron RNA acts as a ribozyme, catalyzing its own splicing

Plays structural and catalytic roles in spliceosomes, the complexes of protein and RNA that splice pre-mRNA