Bio Exam 5

• DNA

  deoxyribonucleic acid
• nucleotide


  monomer of nucleic acids
• binding rules of DNA

  A binds to T, C binds to G
• nucleotide structure

  phosphate group, sugar (deoxyribose in DNA, ribose in RNA), and nitrogenous base
• Erwin Chargaff


  discovered that A=T and G=C
• Rosalind Franklin


  Used X-ray diffraction to discover the double-helical structure of DNA (was unable to confirm shape)
• James Watson and Francis Crick


  discovered the structure of DNA
• template strands


  the original parent DNA strands that is used as a template in DNA replication
• replication fork


  A Y-shaped region on a replicating DNA molecule where new strands are growing (like a fork in the road)
• helicase


  An enzyme that untwists the double helix of DNA at the replication forks (breaks the H-bonds)
• single strand binding proteins


  coat the DNA strands to prevent them from re-forming a double helix
• Topoisomerase


  enzyme that travels slightly ahead of the replication fork, and stops the strands from coiling (as a result of the work of helicase)
• primase

  An enzyme that joins RNA nucleotides to make the primer.
• primers


  starting point for DNA synthesis, short structures of nucleotides (about 10)
• DNA polymerase


  Enzyme involved in DNA replication that joins individual nucleotides to produce a DNA molecule
• dNTPs

  deoxynucleotide triphosphates, help provide energy to DNA replication once its strip of its phosphates
• Pyrophosphate


  PPi, result of dNTPS stripped of their phosphates
• leading strand


  The new continuous complementary DNA strand synthesized along the template strand in the mandatory 5' to 3' direction.
• lagging strand


  A discontinuously synthesized DNA strand that elongates by means of Okazaki fragments, each synthesized in a 5' to 3' direction away from the replication fork.
• Okazaki fragments


  Small fragments of DNA produced on the lagging strand during DNA replication, joined later by DNA ligase to form a complete strand.
• replication bubble


  a region of DNA, in front of the replication fork, where helicase has unwound the double helix (large open region, look like a bubble)
• mismatches


  wrong base pairing in DNA. very rare (1 in 100 million), needs repair if not caught by DNA polymerase
• telomeres


  ends of linear chromosomes (TTAGGG), get shorter with every cell division until it can no longer divide
• telomerase

  protein and RNA enzyme complex, prevents chromosome from shortening while carrying a single strand of RNA template (only active in germ cells)
• nucleosome


  repeating subunit of chromatin fibers, consisting of DNA coiled around histones (a histone octamer plus an H1 linker)
• regulatory sequence


  site for the binding of regulatory proteins (who's role is to influence the rate of transcription)
• transcription stages


  initiation, elongation, termination
• transcription : initiation

  The promoter functions as a recognition site for sigma factor. RNA polymerase is bound to sigma factor, which causes it to bind to the promoter. Following binding, the DNA is unwound to form an open complex
• promoter


  region of DNA that indicates to an enzyme where to bind to make RNA
• transcription : elongation


  sigma factor is released , RNA polymerase slides along the DNA in an open complex to synthesize RNA
• sigma factor

  a protein that controls the binding of RNA polymerase to the promoter
• transcription : termination


  When RNA polymerase reaches terminator, transcription stops & RNA chain is released (mRNA)
• promoter and terminator


  transcription starts at the promoter, ends at the terminator
• 5' cap

  a modified form of guanine nucleotide added onto the 5' end of a pre-mRNA molecule
• 3' poly-A tail

  In eukaryotes, a series of 1-200 adenine nucleotides added to the 3' end of an mRNA (prevents degradation, helps bind to ribosomes)
• splicing


  the process of removing introns and reconnecting exons in a pre-mRNA
• exons


  coding regions of DNA
• introns


  noncoding regions of DNA that lie between exons
• UTR

  untranslated region
• spliceosome


  A large complex made up of proteins and RNA molecules that splices RNA by interacting with the ends of an RNA intron, releasing the intron and joining the two adjacent exons.