AP Biology: Transcription & Translation

Central Dogma of Biology

sequence of information flow is DNA → RNA → proteins

RNA

single stranded, ribose is the sugar, nitrogenous bases=A,U,C,G

DNA

double stranded, deoxyribose is the sugar, nitrogenous bases=A,T,C,G

Prokaryotic transcription & translation

all in cytoplasm (no nucleus); mRNA made directly into protein (no splicing); transcription and translation can occur at same time on same strand

Eukaryotic transcription & translation

has nucleus; original mRNA molecule modified and sent to ribosomes for translation

pre-mRNA

newly transcribed and non-edited mRNA (still contains introns)

Messenger RNA

RNA molecule that carries instructions from DNA in the nucleus to the ribosome to direct protein synthesis

Transfer RNA

RNA molecule that carries an amino acid to a ribosome in protein synthesis and uses anticodon to determine correct order of amino acids

Ribosomal RNA

structural component of ribosomes; combined with proteins in the nucleolus to form ribosome subunits

Location of transcription

nucleus (for eukaryotes)

post-transcriptional modifications

GTP "cap" added to 5' end and polyA "tail" added to 3' end; introns are spliced out

Intron

non-coding DNA segment; removed by snRNP before mRNA travels to ribosome

Exon

coding DNA segment that determines traits of organism (codes for proteins)

Post-translational modification

changes that happen to polypeptide after translation in order to make fully folded protein

Point mutation

change in one base pair of a gene (substitution: replace one base with another)

Silent mutation

changes one nitrogen base, but codes for same amino acid

Missense mutation

change in one base codes for another amino acid (example: sickle cell disease)

Nonsense mutation

change in one base codes for a stop codon (makes nonfunctional protein that is terminated early)

Frameshift mutation (insertion or deletion)

mutation affects all nucleotides/codon groupings farther along DNA/RNA code

Transcription

process in which part of the nucleotide sequence of DNA is copied into a complementary sequence in RNA

Translation

Process by which mRNA is decoded and a protein is produced

Start codon (AUG)

Determines the start of translation, triggers assembly of ribosome subunits and sets the codon frame that will be read by tRNA

Active sites of ribosome

E, P, and A

Splicing

process of removing introns from pre-mRNA

Location of translation

ribosome (located in cytoplasm or rough ER)

Transcription factor

A regulatory protein that binds to DNA and affects transcription of specific genes (turns transcription on/off)

RNA polymerase

Enzyme similar to DNA polymerase that transcribes RNA from DNA template in 5'-3' direction

Karyotype

A display of the chromosome pairs of a cell arranged by size and shape.

Translocation

Change to a chromosome in which a fragment of one chromosome attaches to a nonhomologous chromosome.

Inversion

A mutation that occurs when a chromosome piece breaks off and reattaches in reverse orientation