Exam #4

• Semi-conservative replication happens in eukaryotes, while conservative replication happens in prokaryotes

  false
• Replication of DNA begins when a complex of proteins binds to a sequence of DNA called the ___ and begins to "unzip" the strands


  origin
• The two Y-shaped regions where the strands are separating are called forks and they move


  away from each other as they separate the DNA strands
• Two proteins are key player in separating the strands: helicase which actually separates the strands, and topoisomerase which


  relieves the overtwisting of the helix
• What is true about DNA replication?

  In both eukaryotes and prokaryotes, the template strand of DNA is read the template's 3' to 5' direction, while the new strand DNA is synthesized in new strand's 5' to 3' direction
• What is the name of the major DNA-building enzyme used in prokaryotic replication? 


  DNA pol III
• Okazaki fragments


  act as a primer that initiates DNA replication
• During a study of cancer cells, the most likely reason the telomers aren't shortening is that the cancer cells are expressing

  high levels of telomerase
• DNA polymerase occasionally adds the wrong base to the growing strand but can detect the error immediately and correct it by removing the incorrect base. This process is called

  proofreading
• A mutation is


  a permanent, heritable change in DNA base sequence
• Why is cigarette smoke harmful to DNA?

  a component of cigarette smoke can bind to G nucleotides, disrupting the helix
• In a multi-cellular organism like a human, new mutations in occurring in somatic cells- such as skin cells- will be passed to the next generation (from parent to child)

  false
• What can violate the central dogma?

  using the information in a protein to create an RNA molecule & using the information in an RNA molecule to create DNA
• How is the "language" of a molecule made of nucleotides converted into a molecule made of amino acids?

  using the process of translation, according to the genetic code
• A key event in the initiation of transcription involves

  RNA polymerase binding to the promoter region of a gene
• During the elongation phase of transcription, how is RNA polymerase able to "read" the DNA sequence of bases?

  The RNA polymerase can separate the two strands of DNA as it travels, creating a small window or "bubble" between the strands big enough to read the template strand and create the complementary RNA copy
• Once transcribed, eukaryotic mRNA typically undergoes substantial processing that includes

  removal of intron sequences, addition of a 3' ply-A tail, and addition of a 5' G-cap
• Which is a valid mature mRNA that could be made from it?

  all letters (2356)
• Alternative splicing


  results in the production of different version of proteins from a single gene
• Translation always begins at the 


  start codon
• The sequence of a gene was changed (mutated) such that, instead of producing a mRNA with the codon CUU, it produced an mRNA with CUG. This change (CUU to CUG) is considered a

  silent mutation
• The gene sequence was changed in a different way, such that instead of producing a mRNA with the codon UCG, it produced an mRNA with UAG. This change (UCG to UAG) is considered a

  missense mutation
• What is an anticodon, and where are they found?


  Anticodons are complementary to codons, and are part of tRNA molecules
• While specifics vary between prokaryotes and eukaryotes, in a general model for the initiation of translation, the small subunit of the ribosome and a special tRNA for methionine assemble at the start codon nearest the 5' end of the mRNA. Then the large subunit joins the complex
• What kind of bonds are created between amino acids during the elongation phase of translation?

  covalent peptide bonds
• What binds to stop codons?

  a protein release factor
• Where is the default location for translation to occur?


  in the cytoplasm
• If a finished protein needs to end up in a specific organelle, such as the nucleus or a peroxisome, how will it get there?

  signal sequences on the protein will interact with receptors on the organelle
• The ribosomes on the rough endoplasmic reticulum (RER) are permanently attached there, and specific mRNAs are delivered to them for translation

  false
• At what levels do eukaryotes regulate gene expression?

  at the epigenetic, transcriptional, translational, and post-translational levels
• The expression levels of each gene within an operon can be individually regulated

  false
• IF lactose isn't present in the environment of an E. coli, what is the state of the lac operon?

  It is "off" (no transcription) and the repressor will be bound to the operator
• Where does allolactose, the inducer of the lac operon, bind?

  to the repressor
• If the lac operon is "on" and transcribed, what is produced by RNA polymerase?

  RNA polymerase makes one long mRNA (containing the coding regions of all three genes) which is then translated into the three separate proteins