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Stack #4586774
| Term | Definition |
|---|---|
| British bacteriologist Frederick Griffith studied | strep |
| T2 has a simple structure: a protein coat, called the | capsid with a nucleic acid core |
| Life cycle of a bacteriophage | Attachment, Penetration,Biosynthesis,Maturation,Lysis |
| The relative concentrations of the four nucleotide bases varied from species to species, but not within | tissues of the same indivudual |
| DNA is a polymer of nucleotides made up of a | nitrogenous base, a pentose sugar, and a phosphate group. |
| A and T form | two hydrogen bonds |
| C and G form | three hydrogen bonds |
| Maurice Wilkins and Rosalind Franklin investigated the structure of DNA using | X ray crystallography. |
| Franklin’s X-ray image allowed Watson to infer that DNA consisted of two intertwined strands, | dna helix |
| Pyramindines have a | 6 membered ring structure |
| Watson and Crick first assumed that | identical bases are paired together |
| Conservative Model | The original (parental) DNA stays together; daughter strands form a completely new double helix. |
| Semi-Conservative Model | Each parental strand acts as a template, producing DNA molecules |
| Dispersive Model | Both DNA copies contain interspersed segments of old and newly synthesized DNA. |
| Semiconservative Replication | Matthew Meselson and Franklin Stahl designed an experiment in 1958 to test the mechanism for DNA replication |
| Replication begins at the | origins of replication |
| replication proceeds | bidirectionally |
| DNA polymerase adds | nucleotides to the template |
| DNA pol III | main enzyme |
| DNA pol I & II | primary repair |
| Pol I | removes primers |
| As the origin of replication grows, the unwinding of DNA forms | two replication forms that go in opposite directions |
| Helicase | unwinds DNA |
| Single-strand binding proteins | prevent re-annealing of double strand DNA molecules |
| RNA primase synthesizes | short RNA primers |
| DNA polymerase can only | Add nucleotides in a 5' → 3’ direction. Add to a free 3'-OH group |
| Leading strand will | synthesize one strand of DNA in a 5 to 3 direction |
| the Lagging strand will | be ligated to the leading strand by the enzyme DNA ligase |
| Eukaryotic chromosomes are linear | creating end-replication challenges |
| Telomerase is typically active in germ cells and adult stem cells, but not active in | adult somatic cells |
| Errors arise when DNA polymerase inserts an | incorrect base |
| Unrepaired mistakes may lead to | mutations |
| Most replication errors are corrected immediately by DNA polymerase’s | proof reading function |
| Incorrect nucleotides are removed via | polymerases 3′→5′ exonuclease activity |
| Some replication errors escape proofreading and are fixed after replication via | mismatched repair |
| If mismatches remain uncorrected, they can become | permeant mutations |
| Genetic information flows from DNA to mRNA to protein is described by the | central dogma |
| Transcription | the synthesis of a messenger RNA (mRNA) using DNA as a template |
| Translation: | is the synthesis of a polypeptide using the mRNA as a template |
| Ribosomes are the site of | translation |
| Codons 1-3 | amino acid 1 |
| 4-6 | amino acid 2 |
| meaning more than one codon can specify for an | amino acid |
| However, the genetic code is not ambiguous – meaning | no single codon specifies for more than one amino acid |
| out of 64 codons, 3 are | stop codons |
| a deletion of two nucleotides shifts the reading frame of an mRNA and changes the entire protein message, creating a | nonfunction protein |
| Prokaryotes often contain plasmids which are, | small, circular DNA molecules with one or a few genes |
| Prokaryotic transcription begins when the DNA | partically unwinds |
| For each gene, transcription uses the same DNA strand, called | the template strand |
| Prokaryotic genomes are compact, and a single mRNA transcript often includes | multiple genes |
| Prokaryotic genomes are compact, and a single mRNA transcript often includes | all genes |
| In E. coli, RNA polymerase has five subunits: | α, α, β, β′, and σ |
| required for assembly of the polymerase on DNA. | a subunits |
| binds incoming ribonucleoside triphosphate | B subunits |
| binds the DNA template strand | B' subunits |
| Without σ, the core enzyme would | begin transcription randomly |
| The complete enzyme with all five subunits (core + σ) is called | the holoenzyme |
| The +1 site (initiation site) is the | he first 5′ mRNA nucleotide is transcribed |
| is a DNA sequence where RNA polymerase and associated factors bind | A promotor |
| Promoters are typically located | upstream |
| The promoter sequence influences | how often a gene is transcribed |
| After σ binds the consensus sequences, | RNA core binds to to the promotor |
| Elongation begins when the | σ subunit is released from RNA polymerase |
| RNA polymerase adds nucleotides at a rate of | 40 nucleotides per second |
| Rho-Dependent Termination | requires rho protein |
| Rho-Independent Termination: | Depends on specific DNA sequence signals, not proteins |
| In prokaryotes, the newly made mRNA is often already being translated before transcription finishes, creating a | polyribosome |
| In eukaryotes, the nucleus prevents | simultatnous translation and transcription |
| The TATA box is located about | –25 to –35 bases upstream |
| A–T bonds are thermodynamically weak, helping the DNA | unwind |
| Basal transcription factors recruit RNA polymerase II to | protein coding genes |
| 5′ capping | stabilizing regulatory factors to the 5 end |
| 3′ polyadenylation | addition of a poly-A tail at the 3′ end. |
| Splicing | removal of introns and joining of exons. |
| Pre-mRNA splicing involves the precise removal | of introns from the primary RNA transcript |
| The splicing process is catalyzed by protein complexes called spliceosomes that are composed of proteins | and RNA molecules called small nuclear RNAs |
| tRNAs are structural | RNA molecules transcribed by RNA polymerase III |
| tRNAs act as | adaptor molecules |
| Aminoacyl-tRNA synthetases catalyze covalent bond formation between the tRNA and the correct amino acid in preparation | for translation |
| There are at least 20 different aminoacyl tRNA | synthetase |
| Eukaryotes where are the ribosomes found | cytoplasm and rough er |
| Ribosome Subunits: dissociate into | large and small subunits when not actively translating |
| A site | entry site for incoming charged tRNAs |
| P site (Peptidyl): | holds the tRNA carrying the growing polypeptide chain. |
| E site (Exit): releases uncharged | tRNAs after their amino acid is used |
| Stages of translations | Initiation, Elongation, Termination |
| Translation begins when an initiator tRNA anticodon (Met) recognizes a | Start Codon on a ribosomal subunit |
| Translation for prokaryotes | The Shine–Dalgarno sequence (AGGAGG) |
| translation for eukaryotes | the Kozak sequence (5′-gccRccAUGG-3′) where, R = A or G |
| During elongation, amino acids are added one by one to the | C terminus |
| Elongation occurs in three steps | codon recognition, peptide bond formation, and translocation |
| Energy expenditure occurs in the | codon recognition and translocation |
| In Elongation, the mRNA codons | determine when charged TRNA binds next |
| tRNAs move from | A → P → E |
| Elongation continues until a | stop codon reaches the A site |
| A release factor recognizes the | stop codon and instructs peptidyl to add water to the molcule |
| Secreted proteins contain an | N terminal signal sequence |
| The N terminal sequence is | recognized by SRP |
| From the ER, proteins are exported from the cell through | Vesticle traffiking |
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ecoesfeldd