nucleic acids and DNA

• what is the monomer that forms DNA and RNA?

  Nucleic acids
• what are the two types of nitrogenous bases?

  Purines and pyrimidines
• Which bases are purines?

  Adenine and Guanine.
• which bases are pyrimidines?

  Cytosine, Thymine, and Uracil.
• what is the difference between purines and pyrimidines?

  Pyrimidines are made of one carbon ring, but purines have 2
• what type of sugar is in RNA?


  Ribose
• What type of sugar is in DNA?

  Deoxyribose
• Describe the structure of the nucleic acid that forms a DNA monomer?

  A DNA nucleotide contains a nitrogenous base, a phosphate group and deoxyribose.
• Describe the structure of the nucleic acid that forms an RNA monomer?

  Contains a nitrogenous base, a ribose sugar and a phosphate group
• why is it important that thymine (or uracil) is complementary to adenine and guanine is to cytosine?

  This means that a purine and pyrimidine base are always complementary to each other and complementary base pairing is important to help maintain the order of the genetic code when DNA replicates.
• what reaction occurs for two nucleotides to form into a polymer?

  condensation
• What bond forms between two nucleotides after condensation?

  Phosphodiester bond
• Where does a phosphodiester bond form between two nucleotides?

  Between the pentose sugar of one nucleotide and the phosphate group of the other.
• describe the structure of ATP?

  Adenine, ribose, and three phosphate groups.
• what reaction takes place to make ATP and which enzyme is needed?

  Condensation reactions take place with ATP synthase
• what is the purpose of DNA?

  It codes for the sequence of amino acids in the primary structure of a protein which determines the final 3D structure and function of the protein.
• Describe the structure of DNA?

  A polymer that is formed of two anti parallel strands joined together by hydrogen bonds between complementary bases to form a double helix.
• Why is the DNA structure very stable?

  The sugar phosphate backbone and double helix are formed of covalent bonds which are hard to break down.
• Why is the double stranded nature of DNA beneficial?

  Both strands can act as templates for DNA synthesis or protein synthesis
• why are the weak hydrogen bonds between bases advantageous?

  Easy separation of the strands in a double helix during replication
• what is the benefit of the complementary base pairing?

  Identical copies to strands can be made
• Why is the large size of a DNA molecule beneficial?

  It can carry lots of information
• what are the three types of RNA?

  Messenger (mRNA)

  Transfer (tRNA)

  Ribosomal (rRNA)
• what is mRNA ?

  A copy of one gene from DNA
• Where is mRNA formed?

  it is created in the nucleus and then it leaves via nuclear pores to carry the copy of the genetic code to a ribosome in the cytoplasm.
• Why is mRNA shorter than DNA?

  It is a copy of one gene
• what is a codon and what does it code for?

  A codon is 3 bases in a strand of mRNA, it codes for one specific amino acid,
• where is tRNA found?

  in the cytoplasm
• What is the shape of tRNA and why does it look like that?

  Cloverleaf, due to base pairing and folding held together by hydrogen bonds
• What is the purpose of tRNA?

  To carry amino acids to the ribosome during protein synthesis.
• How is a codon brought to the ribosome by tRNA?

  tRNA has an anticodon, 3 bases that are complementary to 3 bases on the mRNA
• why is DNA replication described as semi conservative?

  When replication takes place, one strand is conserved and another is created.
• When do Mutations occur?

  Copying errors in DNA replication can occur randomly and spontaneously, this can result in a change to the DNA base sequence AKA a mutation.
• in which part of the cell cycle does DNA replication occur in?

  the S aka synthesis phase
• when describing the DNA double helix, the top and bottom of each strand are described as a 3' Prime 5' Prime end- what does this mean?

  This number refers to which carbon within the deoxyribose sugar of the nucleotide is closest to the top or the bottom of the strand.
• what is the relevance of the 3' or 5' ends in terms of semi conservative replication of DNA?

  The enzyme which catalyses DNA replication is complementary in shape to the 3' end and can only attach to the DNA in that location.
• what are the three special features about the genetic code?

  Degenerate

  Universal

  Non overlapping
• What does it mean that the genetic code is degenerate?

  Amino acids are coded for by more than one triplet of bases.
• what does it mean that the genetic code is universal?

  The same triplet of base codes for the same amino acid in all organisms
• what does it mean that the genetic code is non-overlapping?

  Each base in a gene is only part of one triplet of bases that codes for one amino acid. So, each codon, or triplet of bases, is read as one discrete unit.