lesson 1

• DNA


  Stores the information that the cell needs to produce proteins
• DNA


  • It is a double helix
  • Many scientists collaborated in the discovery of its structure
• Nucleotides


  The components that make up DNA
• Adenine (A)


  Binds to Thymine (T)
• Guanine (G)


  Binds to Cytosine (C)
• Hydrogen bonds


  Connect complementary DNA strands
• A gene is a sequence of DNA that encodes a specific protein
• Transcription


  The process where an RNA molecule is produced that is complementary to DNA
• Translation


  The process where the information in RNA is used to make a protein
• RNA


  A molecule that plays an important role in protein production
• Types of RNA


  • Messenger RNA (mRNA)
  • Ribosomal RNA (rRNA)
  • Transfer RNA (tRNA)
• The main function of DNA is to encode proteins
• Relationship between a gene and a protein

  A gene encodes a specific protein
• Transcription


  1. Initiation

  2. Elongation

  3. Termination
• RNA polymerase


  Binds to the promoter and makes an RNA copy of the gene
• Terminator


  The end of the gene
• Poly A tail and mRNA cap

  Added to the RNA in the nucleus
• Introns


  Removed from the RNA molecule in the nucleus
• Exons


  The parts of the RNA molecule that encode the protein
• The nucleotide sequence of the complementary RNA molecule produced in transcription is AGUCUU
• mRNA modifications


  Poly A tail and mRNA cap added, introns removed
• Translation


  1. Initiation

  2. Elongation

  3. Termination
• Codon


  A three-nucleotide sequence that encodes one amino acid
• Genetic code


  Shows which mRNA codons correspond to which amino acids
• Transfer RNA (tRNA)


  Translates the genetic code
• tRNA binds to an mRNA codon


  And binds to the corresponding amino acid
• The ribosome on the far right has been on the mRNA the longest
• Stop codon


  A release factor binds
• Translation


  The polypeptide detaches from the mRNA and folds into a functional protein
• Translation is efficient when multiple ribosomes attach to an mRNA molecule simultaneously
• The ribosome on the far left


  Has been on the mRNA the longest
• Translation occurs in the cell
• Protein synthesis requires lots of energy
• Cells save energy by only producing needed proteins
• Both prokaryotes and eukaryotes regulate protein synthesis, but in different ways
• Regulation of protein synthesis in prokaryotes


  Genes are organized into operons 1. Promoter 2. Operator 3. Genes encoding enzymes that break down lactose
• No lactose present


  Repressor protein blocks transcription
• Lactose present


  Lactose binds to repressor, transcription proceeds, protein synthesis of lactose-digesting enzymes occurs
• Regulation of protein synthesis in eukaryotes

  Gene regulation starts in the nucleus 2. Gene regulation continues in the cytoplasm
• Cells regulate which genes are expressed at any given time to save energy