Nucleic Acids

• What do both DNA and RNA carry?

  Information
• What type of information does DNA hold?

  Genetic information
• What is the role of RNA in relation to DNA?

  Transfers genetic information to ribosomes
• What are DNA and RNA classified as?

  Polymers of nucleotides
• What are the components of a nucleotide?

  Pentose sugar, organic base, phosphate group

  
• What sugar is found in DNA nucleotides?

  Deoxyribose
• What sugar is found in RNA nucleotides?

  Ribose
• What are the organic bases found in DNA?

  Adenine, cytosine, guanine, thymine
• What are the organic bases found in RNA?

  Adenine, cytosine, guanine, uracil
• How do nucleotides join together?

  By phosphodiester bonds in condensation reactions
• What structure does a DNA molecule form?

  Double helix
• How are the two strands of DNA held together?

  By hydrogen bonds between complementary bases
• What is the structure of RNA?

  Single polynucleotide chain
• What is ATP?

  A nucleotide derivative

  
• What are the components of ATP?

  Ribose, adenine, three phosphate groups

  
• What happens when ATP is hydrolysed?

  Energy is released forming ADP and phosphate
• What enzyme catalyses the hydrolysis of ATP?

  ATP hydrolase
• What can the inorganic phosphate from ATP be used for?

  To phosphorylate other compounds
• How is ATP produced during photosynthesis and respiration?

  By condensation of ADP and inorganic phosphate
• What is the purpose of semi-conservative replication of DNA?

  Ensures genetic continuity between generations
• What are the steps of semi-conservative replication of DNA?

  1. Double helix unwinds and hydrogen bonds break
  2. Template strands pair with free nucleotides
  3. Adjacent nucleotides join by phosphodiester bonds

  
• What is the genetic code?

  Order of bases on DNA
• What does each triplet of bases in DNA code for?

  A particular amino acid
• What is a gene?

  A sequence of bases coding for amino acids
• What are introns and exons?

  Introns are non-coding, exons are coding regions
• What are the features of the genetic code?

  • Non-overlapping: each triplet is read once
  • Degenerate: multiple triplets can code for the same amino acid
  • Contains start and stop codons for protein synthesis
• What is the effect of mutations on the genetic code?

  They can alter amino acid sequences
• What are two examples of diseases caused by mutations?

  Cystic fibrosis and sickle cell anaemia
• What are the two stages of protein synthesis?

  1. Transcription (in the nucleus)
  2. Translation (in the cytoplasm)
• What occurs during transcription?

  DNA is transcribed into mRNA
• What are the steps of transcription?

  1. Hydrogen bonds break, DNA uncoils
  2. RNA polymerase uses DNA as a template
  3. Free nucleotides pair and join by phosphodiester bonds
• What is the antisense strand in transcription?

  The DNA template strand used for mRNA
• What happens to mRNA after transcription?

  It moves out of the nucleus to ribosomes
• What occurs during translation?

  • mRNA attaches to a ribosome
  • tRNA collects amino acids and brings them to the ribosome
  • Amino acids join to form a polypeptide chain
• How does tRNA function in translation?

  It carries amino acids to the ribosome
• How do tRNA molecules attach to mRNA?

  By complementary base pairing
• What happens when two tRNA molecules attach to mRNA?

  Amino acids join by peptide bonds
• What signals the end of protein synthesis?

  A stop codon on mRNA