week 2 3

• Nucleus


  The eukaryotic cell's genetic instructions are housed in the nucleus and carried out by the ribosomes

  
• The nucleus contains most of the DNA in a eukaryotic cell

  
• Ribosomes


  Use the information from the DNA to make proteins

  
• Nuclear envelope


  Encloses the nucleus, separating it from the cytoplasm

  
• Nuclear envelope


  • A double membrane; each membrane consists of a lipid bilayer

  
• Nuclear pores


  Regulate the entry and exit of molecules from the nucleus

  
• Nuclear lamina


  Lines the nuclear side of the envelope, composed of proteins that maintain the shape of the nucleus

  
• Nuclear matrix


  A framework of protein fibers throughout the interior of the nucleus

  
• Chromosomes


  Discrete units that DNA is organised into in the nucleus
• Chromatin


  DNA associated with proteins
• Nucleolus


  The site of ribosomal RNA (rRNA) synthesis

  
• Ribosomes


  Complexes made of ribosomal RNA and protein that build proteins

  
• Locations of ribosomes


  • In the cytosol (free ribosomes)
  • On the outside of the endoplasmic reticulum or the nuclear envelope (bound ribosomes)

  
• Free ribosomes


  Suspended in the cytosol

  
• Bound ribosomes


  Attached to the outside of the endoplasmic reticulum or nuclear envelope

  
• Bound and free ribosomes

  • Structurally identical, can alternate between the two roles

  
• Proteins made on free ribosomes


  Function within the cytosol, e.g. enzymes that catalyze the first steps of sugar breakdown

  
• Proteins made on bound ribosomes

  Destined for insertion into membranes, packaging within organelles, or export from the cell (secretion)

  
• Lamins


  The major architectural proteins of the animal cell nucleus, lining the inside of the nuclear membrane

  
• Lamins


  • Provide a platform for the binding of proteins and chromatin, confer mechanical stability

  
• Laminopathies


  Diverse human diseases caused by mutations in lamins
• Hutchinson-Gilford progeria syndrome (HGPS)


  Premature ageing disease caused by a point mutation in the LMNA gene that codes for lamin A
• Chromosomes in interphase


  Less condensed, occupy the entire nuclear space, difficult to distinguish
• Chromosomes in mitosis


  Highly condensed, acquire a discrete 4-armed or 2-armed morphology
• In some organisms like humans, chromosomes are linear (2-50), in others like bacteria, chromosomes are typically circular (1 in general)
• In prokaryotes, the circular chromosome is contained in the cytoplasm in an area called the nucleoid

  
• Histones


  Highly conserved basic nuclear proteins that enable DNA compaction by neutralizing DNA's negative charge

  
• Nucleosome


  The combination of DNA and histone proteins that make up the nuclear content, also referred to as chromatin

  
• Nucleosome


  • DNA wrapped around eight histone proteins that function like a spool

  
• In an interphase chromatin: 45% DNA, 25% histones, 25% other proteins, 5% RNA

  
• Euchromatin


  Less compact chromatin structure, 11 nm fiber with 'beads on a string' appearance
• Heterochromatin


  More compact chromatin structure, 30 nm fiber

  
• Deoxyribose


  The sugar that distinguishes DNA, containing a hydrogen atom at the 2' carbon instead of a hydroxyl group
• Triphosphate group


  Attached to the 5' carbon of the deoxyribose, important for polydeoxynucleotide formation
• DNA


  A polynucleotide consisting of a series of deoxyribonucleotides joined by phosphodiester bonds
• Complementary base pairing


  The regular structure of DNA, with constant orientation, width, distance between nucleotides, length, and number of nucleotides per helical turn
• Denaturation and annealing of DNA


  The process of breaking and reforming the complementary base pairs
• Hyperchromicity (melting profile)


  The change in UV absorbance of DNA during denaturation
• Mitochondrial DNA


  A type of nucleic acid found in mitochondria
• Molecular genetics


  The study of how DNA encodes traits