Exam 5 Review Flashcards
Four Stages of Transcription
- Binding: RN A polymerase binds to a promoter sequence
- Initiation: RN A polymerase then initiates synthesis of RNA using one DNA strand as a template
- Elongation: RNA polymerase moves along the DN A template
- Termination: RNA polymerase dissociates from the DNA template.
Messenger (mRNA)
provides information for production of protein
Ribosomal (rRNA involved in translation)
Major components of ribosomes; guide and catalyze assembly of polypeptides from mRNA during translation
Transfer (tRNA involved in translation)
Bring the correct amino acid to mRNA during translation
Small nuclear RNA s (snRNAs involved in RNA processing)
Form components of the spliceosome; involved in
splicing of eukaryotic RNA s
Small nucleolar RNAs (snoRNAs involved in RNA Processing)
Process rRNAs in nucleolus
Long noncoding RNAs (lncRNAs involved in regulation of gene expression and other events)
Some regulate chromatin; others may regulate transcription or RNA processing
Micro RNA s (miRNAs involved in regulation of gene expression and other events)
Regulate stability and translation of mRNAs
Small interfering RNAs (siRNAs involved in regulation of gene expression and other events)
Small interfering RNAs (siRNAs)* Inhibit production of viruses; suppress spread of
transposable elements in plants
Piwi-interacting RNAs (piRNAs involved in regulation of gene expression and other events)
Suppress spread of transposable elements in germ cells in animals
RNA polymerase I
1.location
2.main products
- Nucleolus
- precursor for 28s rRNA, 18s rRNA, and 5.8s rRNA
RNA polymerase II
1. Location
2. main products
- Nucleoplasm
- Pre mRNAs, most SnRNAs, and micro RNA
RNA polymerase III
1.location
2.main products
- Nucleoplasm
- pre tRNAs, 5 srRNA, and other small RNAs
Mitochondria
1.location
2.main products
- Mitochondria
- Mitochondrial RNA
Chloroplast
1.location
2.main products
- Chloroplast
- chloroplast RNA
The Events of Processing the
Pre-tRNA (4 steps)
- At the 5′ end, a short leader sequence (16 nucleotides) is removed.
- At the 3′ end, the two terminal nucleotides are removed and replaced with CCA.
- About 10–15% of the nucleotides are chemically modified
- An internal 14-nucleotide sequence is removed (an RNA intron), though only for a few tRNA s
Beadle and Tatum
detected link b/w gene mutations and proteins
Linus Pauling
hemoglobin of sickle cells migrates differently from normal hemoglobin
Vernon Ingram
One gene- One polypeptide
Polypeptide theory
nucleotide sequence of a gene determines amino acid sequence of a polypeptide chain
4 Ribosome Sites Appropriate for protein synthesis
- mRNA binding site
- A (aminoacyl) binding site: binds tRNA with attached amino acid
- P (peptidyl) binding site: where tRNA carrying growing peptide resides
- E (exit) site: where tRNAs leave the ribosome discharging their amino acid
Aminoacyl tRNA synthesis (4 steps)
- amino acid and ATP enter the active site
- AMP is joined to amino acid, accompanied by release and breakdown of pyrophosphate
- AMP is displaced by tRNA creating an aminoacyl tRNA
- aminoacyl tRNA is released from enzyme
Mechanisms of translation (3 Steps)
- initiation: mRNA is bound to the ribosome and positioned for translation
- Elongation: amino acids are sequentially joined via peptide bonds
- termination: mRNA and the polypeptide are
released from the ribosome
Eukaryotic Initiation (6 steps)
- eI F2 (with GTP attached) binds to the initiator tRNA^Met before the tRNA
- mRNA is readied to bind the 43S preinitiation complex
- The two complexes join because of interactions between eI F4G and eI F3 and between the small ribosomal subunit and mRNA
- eI F2 hydrolyzes associated GTP, allowing several eI Fs to leave
- After binding to mRNA, the small ribosomal subunit (with tRNA^Met) scans along the mRNA and begins translation at the first AUG
- after the initiator t RN A becomes paired with the start codon, the large ribosomal subunit joins the complex
