W2

• Exons are sequences of DNA that code for proteins
• Regulatory DNA Sequences are DNA components that ensure DNA is expressed at the right time, in the right cell, and in the right amount
• Replication origin


  Nucleotide sequence at which DNA duplication begins
• Telomeres


  Specialized DNA sequences at the ends of chromosomes that allow them to be efficiently replicated and protect them from destruction by the cell
• Histone H1


  Histone that changes the path of DNA exiting the nucleosome to help compact the nucleosome chain
• Constitutive heterochromatin


  Heterochromatin that permanently condenses many regions of the genome
• Heterochromatin


  Highly condensed form of chromatin
• Histone


  Core protein complex of nucleosomes that DNA wraps around
• Histone Octamer


  Protein complex around which DNA wraps composed of 2 of each histone H2A, H2B, H3, and H4
• Centromere


  Specialized DNA sequence that holds duplicated and condensed chromosomes together before being pulled apart by mitotic spindles
• Introns are sequences of DNA that do not code for proteins
• Nucleosome Sliding


  Nucleosomes moving up and down DNA because of ATP-dependent chromatin remodeling complexes loosening DNA wrapped around histones and moving them up and down
• Topoisomerases


  Enzymes that regulate DNA supercoiling
• Epigenetic inheritance


  Cell memory that is not based on an inherited change in DNA sequence
• Chromatin


  Complex of Nuclear DNA in eukaryotic cells and histones and non-histone chromosomal proteins
• Euchromatin


  All other non-highly condensed forms of chromatin
• Nucleosome


  Histone with DNA wrapped around it
• Terminal Tail


  Section of each histone that can experience covalent modification to mark sections of DNA for further packing or unpacking
• Epigenetics


  Inheritance of DNA packing patterns that influence gene expression
• Phosphate groups


  Part of DNA that carries a negative charge on DNA
• Acetylation


  Creates a more open structure of chromatin
• Epigenetics also involves covalent modifications to DNA that silence genes through methylation
• Histone tails


  Location of methylation, acetylation, and other covalent modifications to histones
• Histone H1 is also known as linker histone
• Histone demethylases


  Enzymes that remove methyl groups
• 30 nm fiber


  Stacking of nucleosomes that leads to about a 40-fold packing ratio
• Cytosine


  DNA base that can be methylated
• Histone deacetylases


  Enzymes that remove the acetyl groups from histone tails
• Looped domain


  Loops of 30 nm fiber created by chromatin being attached to protein scaffolding
• DNA Methyltransferase


  Enzyme that can add methyl groups to the DNA at the site where C is followed by G
• DNA methylation prevents the initiation of transcription
• Histone methyltransferase


  Enzymes that add methyl groups to lysine or arginine residues
• Methylation


  Creates a more closed structure of chromatin to silence genes
• Histone acetyltransferases


  Enzymes that acetylate histone proteins by transferring acetyl group from acetyl-CoA to specific lysine residues
• Facultative heterochromatin


  Heterochromatin that can be regulated to control gene expression