bio 101

• 1. replication
  2. DNA
  3. transcription
  4. reverse transcription
  5. RNA
  6. translation
  7. polypeptides
  8. post-translational modification
  9. proteins
  10. traits

  
• In transcription, dna is used as template to make rna
• in translation, rna is used to synthesize polypeptides
• Polypeptides are folded and modified to make proteins
• in reverse transcription, rna is used as a template for dna
• It is not always required that a gene is transcribed then translated to determine a trait, sometimes it is enough that a gene is simply transcribed then rna will then affect a trait
• 7 characters of gregor Mendel's experiment

  1. height
  2. seed shape
  3. seed color
  4. seed coat color
  5. pod shape
  6. pod color
  7. flower position
• molecular basis of seed shape

  1. sbe 1 gene
  2. transcription
  3. sbe 1 rna
  4. translation
  5. starch branching enzyme
  6. round seed

  
• if plant has sbe 1 gene, it will transcribe it and produce sbe 1 rna which produces starch branching enzyme and produces round seeds
• sbe catalyzes branching of glucose to produce starch

  in dominant - with sbe, glucose will branch, starch less soluble in water, seed mature (dry out), no water will come out, round shape maintained

  recessive - without sbe, just glucose, more soluble, water will come in, in maturation (drying out) water will come out and seed wrinkled
• Le gene - gene responsible for plant height
• le gene -- le rna - gibbrelin 3b hydroxylase - tall plant
• gibbrellin 3b hydroxylase - one of enzymes required for gibberelic acid synthesis

  gibbrelic acid - hormones that makes the plant tall
• Transcription: universal feature

  DNA-dependent RNA synthesis

  Template - DNA anti-coding/antisense strand ( 3'-5' strand)

  mrna same with sense strand
• sense strand contains the same sequence as mrna
• Transcription: universal features

  DNA-dependent RNA synthesis

  products:

  Messenger RNA (mRNA)

  Ribosomal RNA (rRNA)

  Transfer RNA (tRNA)

  miRNA, siRNA and other regulatory RNAs
• Transcription: universal features

  Involves only certain regions of the DNA template

  • coding regions - DNA sequence that code for an RNA molecule
  • Non-coding regions - Do not code for an RNA molecule, Have important roles in switching the gene “on” or “off”, Ex. centromeres, telomeres, promoter
• Central Dogma of Molecular Biology

  describes the flow of genetic information from the sequence of the gene in the DNA to the synthesis of proteins which are responsible for the expression of traits of an organism
• transcription: copying of the gene sequence in the DNA
• mRNA: copy of the sequence or “transcript”
• translation: polypeptide synthesis using the mRNA template
• polypeptides will undergo further structural modifications before becoming a biologically active protein that would be responsible for manifesting the trait or phenotype
• tRNA, rRNA, other regulatory RNA: also produced via transcription and undergo post￾transcriptional modifications different from an mRNA to become biologically active
• prokaryotes: only RNA-coding regions are transcribed−

  eukaryotes: coding and non-coding regions are transcribed first, then the non-coding regions are removed
• Transcription: Universal Features

  Three general steps•

  Initiation•

  Elongation

  termination

  Major control point of gene expression• At the initiation step
• initiation: major control point of regulation of gene expression
• transcription

  Uses RNA polymerase as the main enzyme• A DNA-directed RNA polymerase• Uses DNA as the template
• dna directed rna polymerase means that it uses dna as template
• RNA polymerase: major enzyme in transcription which uses DNA as a template to produce RNA
• transcription unit: basic unit of a gene that extends from the promoter region to the termination sequences
• Give similarity of rna pol and dna pol in terms of cofactor


  they both have Mg2+ as cofactor
• rna and dna pol; substrate 


  rna pol: rntps

  dna pol: dntps
• rna and dna pol: primer


  rna - do not require primer

  dna - require a primer
• rna vs dnapol: synthesizing product 


  rna pol - absolutely progressive enzyme -- synthesize each product in just 1 go

  dna pol - synthesizes dna segmentaly/ bisegmentally (discontinuous)
• rna vs dna pol: proofreading

  rna - weakerproof reading (1/10^7)

  dna- excellent proof reading 1/1B errors( 1/10^9)
• transcription unit


  RNA-coding sequence; the region from start site (+1) to termination site
• +1 position


  start site
• part of gene not transcribed, why?


  promoter, non coding dna region
• primary transcript


  Immediate, unaltered product of the RNA polymerase action 😭
• after processing, primary transcript shortens