| A | B |
|---|
| transformation | a change in genotype and phenotype due to assimilation of foreign DNA |
| double helix | DNA is two strands that wind around each other |
| complementary base pairing | a purine (A or G) is always bound to a pyrimidine (T or C) |
| antiparallel | describes the two strands of DNA which go in opposite directions |
| DNA replication | the process of copying a DNA molecule |
| template | a single strand of DNA can be used to determine which bases need to be incorporated into the complementary strand |
| semiconservative replication | each daughter double helix contains an old strand from the parental DNA and a new strand (daughter) |
| DNA helicase | unwinds the DNA and separates the parental strands |
| single-stranded binding proteins (SSB) | attach to newly separated DNA and prevent it from re-forming the helix so replication can occur. |
| DNA primase | places short primers (short strands of RNA) on the DNA strands to be replicated, provides a place for DNA polymerase to bind |
| DNA polymerase | Synthesizes DNA in leading and lagging strands, removes RNA primers filling in the gaps with more DNA and proofreads the newly made DNA |
| DNA ligase | covalently attaches adjacent Okazaki fragments in the lagging strand |
| Okazaki fragments | short fragments of DNA synthesized on the lagging strand that runs in the opposite direction of DNA synthesis |
| relication bubble | a segment of the DNA that has been unwound |
| Topoisomerase | relieves the strain caused by tight twisting ahead of the replication fork by breaking, swiveling, and rejoining DNA strands |
| messenger RNA (mRNA) | takes a message from DNA in the nucleus to the ribosomes in the cytoplasm |
| transfer RNA (tRNA) | transfers amino acids to the ribosomes |
| ribosomal RNA (rRNA) | along with ribosomal proteins, makes up the ribosomes, the protein synthesis machinery |
| transcription | RNA molecule is produced based on the DNA template |
| translation | the mRNA transcript is read by the ribosome and converted into a sequence of amino acids in a polypeptide |
| central dogma | the flow of information from DNA to RNA to protein |
| genetic code | the set of codons that produces the 20 amino acids in proteins |
| codon | a set of three nucleotides that represent a coding unit in the genetic code |
| degenerate (or redundant) | most amino acids have more than one codon |
| RNA polymerase | synthesizes the RNA strand in the 5' to 3' direction |
| promoter | defines the start of transcription, the direction of transcription, and the strand to be transcribed |
| transcription initiation | binding of the RNA polymerase to the promoter |
| transcription elongation | RNA polymerase reads down the template strand in a 5' to 3' direction and continues until it reaches a DNA stop sequence |
| transcription termination | The stop sequence causes RNA polymerase to stop transcribing the DNA and release the mRNA molecule, now called an mRNA transcript (or primary transcript) |
| exons | protein coding regions of a gene, these are expressed |
| introns | noncoding regions of a gene, these are not expressed |
| ribozyme | an enzyme made of RNA rather than just proteins that cuts and removes introns |
| spiceosome | the splicing machinery (contains snRNAs, ribozyme) |
| small nuclear RNAS (snRNAs) | by complementary base pairing, identify the areas that need to be removed |
| alternative mRNA splicing | the presence of introns allows a cell to choose which exons will go into a particular mRNA |
| microRNAs (miRNAs) | some introns give rise to these, small molecules involved in regulating the translation of mRNAs |
| anticodon | a group of three bases that is complementary and antiparallel to a specific mRNA codon |
| aminoacyl-tRNA synthetases | attach the correct amino acid onto the correct tRNA |
| polyribosome | the entire complex of mRNA and multiple ribosomes |
| translation initiation | initiation factors assemble the small ribosomal subunit, mRNA, initiator tRNA, and the large ribosomal subunit for the start of protein synthesis |
| translation elongation | stage during protein synthesis when a polypeptide increases in length one amino acid at a time |
| translocation | the ribosome moves forward, and the peptide-bearing tRNA is now in the P site of the ribosome and the spent tRNA leaves the E site |
| translation termination | occurs at a stop codon which codes for a release factor that binds to the A site on the ribosome and cleaves the polypeptide from the last tRNA |
| gene expression | A gene is expressed once its product, a protein or RNA, is made and is operating in the cell, includes both transcription and translation |
| telomerase | An enzyme (mutated in many cancers) that regulates the length of telomeres, normally has very low (almost undetectable) activity in somatic cells |
| telomeres | the ends of eukaryotic chromosomes |
| promoter | defines the start of transcription, and the strand to be transcribed, where the RNA polymerase binds |
| Free nucleotides | used by DNA and RNA polymerase during replication and transcription to synthesize new strands of DNA or RNA |
| pre-mRNA (primary transcript) | a newly formed RNA transcript that has not yet undergone post-transcriptional processing in eukaryotic cells |
| 5' cap | modified guanine nucleotide that helps tell a ribosome where to attach when translation begins, helps to stabilize the mature mRNA |
| 3' poly A tail | a chain of 150-200 adenine nucleotides subsequent to a polyadenylation signal sequence that facilitates transport out of the nucleus, helps initiate loading of ribosomes, and delays degradation of mRNA by hydrolytic enzymes |
| tRNA-MET | initiator tRNA, attaches to the start codon and carries methionine |
| P site | peptide site on ribosome, where the initiator tRNA binds to AUG and where the growing polypeptide chain is located |
| A site | amino acid (or additional) site, where the next tRNA binds during elongation |
| E site | empty (exit) site, where the empty tRNA exits the ribosome after it has attached its amino acid to the growing peptide chain |
| release factors | proteins that bind to a stop codon and cleave the polypeptide from the last tRNA |
| signal peptide | the first few amino acids of a polypeptide that indicates where the polypeptide belongs in the cell or whether it is secreted |
