Backlecture 14
Terms in this set (24)
tRNA acts as an adapter that carries amino acids to the ribosome and matches its anticodon with the mRNA codon to translate RNA sequence into a protein sequence.
The genetic code is a triplet code where each group of 3 mRNA bases (codon) corresponds to one amino acid.
An anticodon is a group of 3 bases in tRNA that is the reverse complement of the mRNA codon and pairs with it during translation.
The amino acid is covalently linked to the 3' OH of the tRNA via an ester bond, catalyzed by aminoacyl-tRNA synthetase, using energy from pyrophosphate hydrolysis.
Hydrolysis of PPi provides energy for covalent bond formation in replication, transcription, ligation, and amino acid loading on tRNA, releasing two phosphoanhydride bonds.
The wobble position is the third base of the codon (first of anticodon) which allows flexible base pairing, reducing the number of tRNAs needed.
There are 64 codons total: 61 code for amino acids and 3 are stop codons signaling termination of translation.
The ribosome has three sites: A site (aminoacyl-tRNA binding), P site (peptidyl-tRNA binding), and E site (exit site for deacylated tRNA).
The large ribosomal subunit catalyzes peptide bond formation between amino acids attached to tRNAs in the P and A sites.
mRNA is read in the 5' to 3' direction, and the protein is synthesized from the N-terminus to the C-terminus.
Translation initiation involves the small ribosomal subunit binding mRNA and initiation factors, initiator tRNA binding the start codon (usually AUG), then the large subunit joining.
Two GTP molecules (2 ATP equivalents) are hydrolyzed per amino acid added during elongation: one for tRNA selection and one for translocation.
When a stop codon enters the A site, release factors bind, hydrolyze the bond between the polypeptide and tRNA, and GTP is hydrolyzed to release the ribosome components.
Mutations include point mutations (single base changes), insertions, deletions, silent mutations (no amino acid change), and frameshift mutations (shift reading frame).
An SNP is a point mutation that may be silent, disease-causing, or protective, and is the most common genetic variation among humans.
PCR requires DNA polymerase, DNA template, two primers (one for each strand), and dNTPs, with thermal cycling to denature and replicate DNA.
Each PCR cycle doubles the amount of DNA, leading to exponential amplification (2^n after n cycles).
Recombinant DNA involves inserting a gene of interest into a plasmid vector, which can be propagated in bacteria to produce DNA, RNA, or protein.
Restriction enzymes cut DNA at specific sequences, often creating sticky ends that allow complementary base pairing for insertion of DNA fragments into plasmids.
DNA is negatively charged and migrates toward the positive electrode through a gel matrix, separating fragments by size for visualization.
RNA viruses replicate using RNA-dependent RNA polymerase to make RNA from RNA or use reverse transcription to convert RNA into DNA.
RT-PCR converts viral RNA into complementary DNA (cDNA) using reverse transcriptase, then amplifies the cDNA by PCR to detect viral genetic material.
The Ct value is the number of PCR cycles needed to detect DNA; a lower Ct indicates a higher initial amount of target nucleic acid.
PCR tests detect viral genetic material, while antigen tests detect viral proteins; antigen tests are faster but less sensitive and may require PCR confirmation.