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43 Cards in this Set

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  • Back
What is the central Dogma of molecular biology?
-DNA, RNA, Protein
What are the informational macromolecules?
-DNA, RNA, Protein
How is information in DNA and RNA encoded?
-by sequence of bases
How is information in protein is encoded?
-in sequence of amino acids
What is a gene?
-segment of DNA that encodes a RNA molecule
-mRNA, tRNA, rRNA
What does polycistronic mean?
-when more than one gene is transcribed into one mRNA of prokaryotes
What does monocistronic mean?
-one gene gets one mRNA (can be prokaryotic or eukaryotic)
What does primary mRNA transcript contain?
-exons and introns
What are exons?
What are introns?
-protein-coding sequences
-intervening sequences
How are introns removed?
-by RNA processing
-RNA must be transported out of nucleus
What are the three stages of Transcription?
-initiation
-elongation
-termination
How does transcription occur?
-in a 5' to 3' direction (concurrent in E. coli)
What does transcription of E. coli require?
-RNA polymerase (one in bacteria)
-multisubunit core enzyme
-sigma factor
What is a sigma factor used for?
How about multiple sigma factors?
-specificity of initiation
-transcription of different genes
How does RNA polymerase (RNAP) work in transcription of E. coli?
-binds promoter sequences 5' to mRNA start site which is determined by Pribnow box and about 35 sequences
What are the two types of termination of transcription?
-self-termination
-protein-dependent terminationd
How does self-termination work?
-only RNAP is needed for termination
-no other protein factors are required
-requires stem-loop formation in RNA and about 6 U residues
How does protein-dependent termination work?
-Rho protein is needed for termination
-requires DNA sequence righ in C residues
-Rho binds mRNA and unwinds RNA-DNA complex
-unwinding causes RNAP to fall off
What is RNA processing?
-conversion of a precursor RNA to a mature RNA
In prokaryotes and eukaryotes, what molecules are made as precusors that are cut to make final mature RNA's?
-tRNA's and rRNA's
In eukaryotes, what do mRNA molecules do?
-made as pre-mRNA precursors; introns are spliced out to make mature mRNA's
What is capping?
-addition of methylated guanine residue to 5' end of mRNA
What is polyadenylation?
-addition of long stretch of A residues to 3' end of mRNA; occurs during termination
What is a spliceosome?
-multiprotein complex
-splicing creates an exon-exon junction and an intron lariat
What is a ribozyme?
-catalytic RNA
-no proteins needed
-found in self-splicing introns
What is a genetic code?
-information that allows nucleic acid sequences to be translated into amino acid sequences in proteins
What is a codon?
-triplet of three bases encoding an amino acid
What is degeneracy of code?
-most amino acids are encoded by more than one codon
-codon usage varies from organism to organism
How does translation occur in protein synthesis?
-base pairing of codon with anticodon on specific charged tRNA molecule
What can computer programs pick out in DNA codes?
-the ORF's (Open-reading frames)
*doesn't prove they are expressed though
What are open-reading frames?
-defined by a start codon, then a number of codons, and lastly a stop codon
What are start codons?
-methionine (AUG)
What are some sotp codons?
-UAA
-UAG
-UGA
Describe tRNA.
-adaptor molecules that contain anticodon that base pairs with codon
-short, single-stranded RNA; 73-93 nucleotides; cloverleaf
-about 60 tRNA's in bacteria (100-110 in mamalian cells)
-each tRNA is specific for an AA that binds to ribose sugar of A residue of CCA acceptor and sequence
What are Aminoacyl-tRNA synthetases?
-enzymes that covalently attach amino acids to tRNA
-must recognize tRNA anticodon loop and specific amino acid
-high degree of fidelity required so that wrong amino acid doesn't get incormporated into polypeptides
What are ribosomes?
-sites of protein synthsis that contain multiple proteins and ribosomal RNA (rRNA)
-free or on rough ER
What are antibiotics?
-inhibit initiation (streptomycin) and elongation (puromycin, chloramphenical, clcyoheximide, tetracycline, kanamycin)
What are the bacteria-specific antibiotics?
How about eukaryote specific?
-streptomycin, chloramphenical
-cycloheximide
How does initiation in translation occur in bacteria?
-16S rRNA base pairs with sequences upstream of start codon
How do eukaryotes begin initiation in translation?
-ribosome recognizes 5' cap and starts at first AUG
What does initiation include for translation?
-complex of 30S small subunit, mRNA, tRNA, and initiation factors (proteins)
What are polysomes and what are they for?
-multiple ribosomes translate the same mRNA; independent events
-increase speed and efficiency
-some nascent proteins fold spontaneously while being synthesized
What are molecular chaperones?
-proteins that assist in the folding of polypeptides post-translation or after denaturation
-do NOT become part of protein
-require energy (ATP)