Gene Expression

  1. Gene expression - the process in which the information encoded in a gene directs the synthesis of a protein; there are two main steps- transcription and translation

  2. Transcription - the process in which the genetic information in DNA is copied into mRNA; the three steps are initiation, elongation,and termination

  3. Messenger RNA - a type of RNA that serves as a template for protein synthesis, carrying the transcribed information from DNA to the ribosomes

  4. Translation - the process in which the genetic code carried by mRNA is translated to synthesis a specific protein

  5. Ribosomes- organelles that synthesize proteins by translating mRNA into amino acids 

  6. Genetic code- the instructions within DNA and RNA that cells use to produce proteins

  7. Codon - a three nucleotide sequence which is code for a specific amino acid to be translated or the code for the end of protein synthesis

  8. Template strand (in the context of transcription)- acts as a base for mRNA transcription

  9. Coding strand - the strand of DNA that does not get read during transcription and instead matches the RNA that gets synthesized (aside from having T’s where RNA has U’s)

  10. Reading frame- the way a sequence of nucleotides in mRNA is sectioned into codons, with three possible frames used to determine the translation of amino acids 

  11. RNA polymerase- is the enzyme that reads a DNA sequence and transcribes it into RNA. 

  12. Promoter - the DNA sequence where RNA polymerase can bind to begin transcription at the start point specific nucleotide

  13. Transcription factor- specific proteins that regulate transcription by attaching to specific DNA sequences by either prohibiting or promoting the transcription process

  14. Transcription initiation complex- a complex of of proteins such as RNA polymerase, that will copy a sequence of nucleotides into an RNA transcript 

  15. TATA box - a portion of a eukaryotic promoter that contains a TATA nucleotide sequence and helps transcription factors and RNA polymerase both recognize and bind to the DNA strand at the right place to start transcription

  16. 5’ cap - a modified guanine nucleotide that gets added to pre-mRNA to help modify it into mature mRNA in order to protect the mRNA and help it get exported from the nucleus

  17. Poly-A tail - a sequence of around 50-250 AAA nucleotides that gets added to the primary transcript of pre-mRNA during RNA modification before it gets sent out to the cytoplasm. This prevents early degradation of RNA and helps with export.  

  18. RNA splicing- is a process by which pre-mRNA becomes mature-mRNA by removing non-coding regions, while joining the coding regions together

  19. Introns - the portions of RNA that get removed during RNA splicing and do not get translated into amino acids

  20. Exons - the portions of RNA that remain in the RNA post-modification and are sent out to the cytoplasm

  21. Ribozyme- RNA molecules that can participate in catalyzing chemical reactions (taking on the role of an enzyme)

  22. Alternative splicing - different ways to splice the same gene, where various combinations of DNA are kept as exons while others are removed as introns. This helps create protein variability, since the same gene can yield different types of proteins, based on which exon sequences in mRNA are sent out to the cytoplasm. 

  23. Transfer RNA- small RNA molecules that transport amino acids to the ribosome, for polymerization so that the amino acids can become polypeptides 

  24. Anticodon - a three nucleotide sequence in a tRNA molecule which matches the complementary codon sequence in a mRNA molecule and binds to the codon

  25. Wobble position - the third nucleotide of a codon, which only loosely binds to tRNA so the matching anticodon doesn’t have to be perfectly complementary, allowing multiple sequences to code for the same amino acid

  26. Ribosomal RNA- catalyzes protein synthesis in the ribosomes

  27. Small ribosomal subunit - decodes the genetic information during protein synthesis by positioning the mRNA and three tRNA molecules

  28. Large ribosomal subunit - catalyzes the formation of peptide bonds during protein translation by linking amino acids together to form polypeptide chains