Nucleic acids

• What are the characteristics of polynucleotides?

  covalent bonds formed via phosphodiester linkages (negatively charged backbone) , Dna backbone is fairly stable , RNA backbone is unstab;e , linear polymer , directionality (5'-3')
• What is the covalent structure model of dna?

  phosphodiester linkages and pentose is ribofuranoside
• What are chargaff rules?

  A = T and G = C
• What is the Watson-Crick model of DNA?

  double helix structure
• What is the Watson crick model of B DNA?

  right handed double helix

  
• What are the characteristics of the hydrogen bonds?

  Two chains differ in sequence, chains are complementary and chains are antiparallel
• What are the other forms of dna?

  A form : right handed , 26A , 11 base pair per turn

  
  

  Z form: Left handed , 18A , 12 base pair per turn
• What are palindromic sequences?


  Sequences that consist of base pairs that read the same in the opposite direction
• How is DNA organized within the cell?

  can take many forms; dna , chromosomes , nucleosomes . Found in nucleolus in euchromatin and heterochromatin
• What does DNA methylation do?

  Regulates: gene expression , chromosomal stability , cell differentiation , imprinting , X chromosome inactivation , carcinogenesis , aging
• What is epigenetics?


  Study of reversible changes in gene function that occur without a change in sequence of nuclear dna
• What are the characteristics of DNA denaturation/annealing?

  Covalent bonds remain intact , hydrogen bonds are broken , base stacking is lost
• What is annealing?


  pairing of a strand of DNA with another strand to form double helix
• What factors affect DNA denaturation?

  Midpoint of melting(Tm) depends on base composition (high CG increases Tm)

  
  

  Tm depends on dna length (the longer the higher Tm) , Tm depends on ph and ionic strength
• What is the structure of RNA?


  Contain ribose and uracil , synthesized using DNA template , single stranded , complex secondary structures
• What is the structure of mRNA?


  single , uncoiled strand , coding and non coding sequences
• What is a unique characteristics of prokaryotic mrna?

  polycistronic
• What is the impact of alternative splicing?

  exons from the same gene are joined in different transcripts , one gene can be encoded into numerous proteins with various functions
• What is the structure of tRNA?


  cloverleaf

  
• What is the process of maturation of tRNA?

  primary transcript undergoes base modification , 5' and 3' cleavage and CCA addition. Intermediate undergoes splicing to produce mature tRNA
• How do mRNA and tRNA interact?

  tRNA anticodon binds to complementary mRNA codon via ester bond
• What are the types of rRNA?

  Bacteria: 23s , 16s , 5s

  Eukaryotes: 28s , 18s , 5.8s , 5s
• What is the ribosome structure?

  rRNA and proteins come together to produce a 60s and 40s subunits (in eukaryotes) which join to make an assembled ribosome 80s
• What is non coding RNA, and why is it important?

  Heterogenous group of transcripts which aren't translated into proteins and can regulate cellular processes (cell division , cell migration , damage repair)