DNA and Protein Synthesis

• The genome is the complete set of genes in an individuals DNA, with the genes in the genome encoding for the different proteins a cell needs.
• The proteome is the full range of proteins a cell can produce
• What is the genome?

  The complete set of genes in an individuals DNA
• What is the proteome?


  The full range of proteins a cell can produce
• The proteome is usually larger than the genome because it includes all the proteins that can be made from the genetic material
• The proteome is usually larger than the genome of an organisms because of the large amount of post-translational modifications of proteins that often occurs in the Golgi apparatus
• Each gene is capable of producing multiple different proteins via alternative splicing
• DNA is made from a combination of four different bases, and a specific sequence of three of these bases, known as a codon, encodes for a specific amino acid.
• How is RNA similar to DNA?

  It is a polynucleotide made up of many nucleotides linked together in a long chain, and contains the nitrogenous bases adenine, guanine and cytosine as well as a pentose sugar.
• How does RNA differ from DNA?

  • DNA is double-stranded, whereas RNA is single stranded
  • DNA uses a base called thymine, and RNA substitutes thymine with a base called uracil
  • DNA’s sugar is deoxyribose, whereas RNA’s is ribose
• RNA is a single stranded nucleic acid molecule that is made from the same bases as DNA, except for uracil, which is used instead of thymine.
• Each RNA polynucleotide is made up of alternating ribose sugars and phosphate groups linked together, with the nitrogenous bases of each nucleotide connected to the ribose sugar.
• What is the name of the sugar-phosphate bonds in nucleic acids?


  Covalent bonds known as phosphodiester bonds
• The phosphodiester bonds in RNA forms the sugar-phosphate backbone, and links the 5-carbon of one ribose sugar to the phosphate group from the same nucleotide, which then links by another bond to the 3-carbon of the next ribose sugar.
• What are the two types of RNA?

  mRNA and tRNA
• What does mRNA stand for?

  Messenger RNA
• What does tRNA stand for?

  Transfer RNA
• Messenger RNA is a linear single stranded molecule transcribed from DNA in the nucleus
• The mRNA strand is complementary to the DNA base sequence it was transcribed from
• After leaving the nucleus, where it is synthesised, mRNA travels to the ribosomes in the cytoplasm where it is involved in protein synthesis.
• Ribosomes are proteins that translate mRNA into amino acids and synthesise the polypeptide
• What biological molecule are ribosomes?

  Proteins
• What is the function of ribosomes?

  They translate mRNA into amino acids and synthesise the polypeptide
• Messenger RNA is produced during transcription in both prokaryotes and eukaryotes
• The mRNA produced during transcription in eukaryotes is called pre-mRNA, which has to be spliced before it enters the ribosome for translation.
• Splicing is a process that removes sections of non-coding DNA called introns from the mRNA molecules in eukaryotes.
• The mRNA produced in prokaryotes is the completed form of mRNA, having no introns, and therefore doesn’t require splicing to occur.
• What is the difference between mRNA in prokaryotes and eukaryotes?


  In eukaryotes, mRNA contains introns that needs to be removed via a process called splicing, whereas prokaryotes dont contain introns
• In prokaryotes, RNA polymerase catalyses every step of transcription, including the separation of the DNA strands and the production of the mRNA strand, whereas, in eukaryotes it only produces the mRNA strand and DNA helicase is the enzyme that separates the DNA strands.
• What is the difference between RNA polymerase in transcription in prokaryotes and eukaryotes?

  In prokaryotes, it catalyses every step of transcription, whereas in eukaryotes it only produces the mRNA strand.
• Transfer RNA forms a clover-like shape and is vital for translation, as it reads the mRNA codons and brings the corresponding amino acid into the ribosomes.
• What is the shape of transfer RNA?

  Cloverleaf
• What is the role of transfer RNA in translation?


  It reads the mRNA codons and brings the corresponding amino acid into the ribosomes
• Each tRNA molecule has an anticodon which is complementary to a specific codon on mRNA
• The amino acid that corresponds to a specific anticodon binds to a specific attachment site on the tRNA molecule.
• A tRNA molecule also does have some hydrogen bonds between paired complementary bases, and less nucleotides than mRNA.
• What are some differences between tRNA and mRNA?

  • tRNA contains less nucleotides than mRNA
  • mRNA has a linear structure, whereas tRNA has a cloverleaf shape
  • mRNA contains no hydrogen bonds, whereas contains some between bases
• Protein synthesis is the process of making proteins in the cells
• There are two processes involved in synthesising proteins from a base sequence, which are transcription and translation
• What is the two processes involved in protein synthesis?


  Transcription and translation