BIOL 330 Exam 2

exceptions to central dogma

RNA replication and reverse transcription

rRNA

structural and functional components of the ribosome

mRNA

carries genetic code for proteins

tRNA

helps incorporate amino acids into polypeptide chain 

pre-mRNA

precursor to mRNA

snRNA

processing of pre-mRNA

snoRNA

processing and assembly of rRNA

miRNA

inhibits translation of mRNA

siRNA

triggers degradation of other RNA molecules

piRNA

suppresses the transcription of transposable elements in reproductive cells

incRNA

transcription of noncoding genes

crRNA

assists destruction of foreign DNA

nucleolus

intranuclear organelle involved in ribosomal RNA synthesis and ribosome assembly

promoter

the DNA sequence where RNA polymerase attaches

template strand

guides the synthesis of the RNA molecule for base pairing 

sigma factor

binds to the promoter when transcription starts in bacteria cells. responsible for promoter recognition 

RNA polymerase holoenzyme

the core enzyme + the sigma factor

consensus sequences

common nucleotide sequences found in highly conserved regions of DNA or RNA or proteins

terminator

the sequence signaling the end of transcription

transcription unit

the stretch of DNA that is transcribed

intrinsic termination (rho-independent)

occurs when a termination sequences is transcribed into RNA, causing the transcript to fold back on itself, forming a hairpin structure 

rho-dependent termination

depends on the rho termination factor to unwind the DNA-RNA hybrid and end transcription

RNA polymerase I

transcribes rRNA in nucleolus

RNA polymerase II

transcribes mRNA in nucleoplasm

RNA polymerase III

transcribes tRNA in nucleoplasm

exons

protein-coding sequences

introns

noncoding sequences

RNA splicing

removal of noncoding introns from pre-mRNA, allows multiple proteins to be produced 

spliceosome 

consists of proteins and snRNA’s that recognize splice sites 

triplet code

a series of nonoverlapping, three-nucleotide words

codon

a three-nucleotide sequence mRNA that specifies a particular amino acid or termination signal. the basic unit of genetic code

RNA homopolymer

RNA nucleotides with only one type of ribonucleotide

polynucleotide phosphorylase

enzyme that catalyzes production of synthetic mRNAs

RNA heteropolymers

RNA nucleotides with two or more different ribonucleosides 

triplet binding assay

used to determine which transfer RNA molecules correspond to specific codons in mRNA

initiator codon

AUG (Met)

termination codons

UAA, UGA, UAG

Open reading frame (ORF)

a continuous sequence of codons in a mRNA or DNA that has the potential to be translated into a protein

point mutation

a single nucleotide base is changed, inserted, or deleted from a genome

silent mutation

change in the DNA sequence of the gene has no effect on the amino acid sequence

missense mutation

still code for an amino acid but not the correct amino acid

nonsense mutation

change an amino acid codon to a stop codon

frameshift mutation

insertion or deletion of nucleotides that alter the reading frame 

the wobble hypothesis

codons for the same amino acid tend to contain the same nucleotides at the first and second positions and vary at the third position

unambiguous

each triplet specifies only one amino acid

degenerate

a given amino acid can be specified by more than one triplet codon