TAILIEUCHUNG - Lecture Biology (7th edition) - Chapter 19: Eukaryotic genomes: Organization, regulation, and evolution

In this chapter, students will be able to understand: Chromatin structure is based on successive levels of DNA packing; gene expression can be regulated at any stage, but the key step is transcription; cancer results from genetic changes that affect cell cycle control;. | Chapter 19 Eukaryotic Genomes: Organization, Regulation, and Evolution Overview: How Eukaryotic Genomes Work and Evolve In eukaryotes, the DNA-protein complex, called chromatin Is ordered into higher structural levels than the DNA-protein complex in prokaryotes Figure Both prokaryotes and eukaryotes Must alter their patterns of gene expression in response to changes in environmental conditions Concept : Chromatin structure is based on successive levels of DNA packing Eukaryotic DNA Is precisely combined with a large amount of protein Eukaryotic chromosomes Contain an enormous amount of DNA relative to their condensed length Nucleosomes, or “Beads on a String” Proteins called histones Are responsible for the first level of DNA packing in chromatin Bind tightly to DNA The association of DNA and histones Seems to remain intact throughout the cell cycle In electron micrographs Unfolded chromatin has the appearance of beads on a string Each “bead” is a nucleosome The basic unit of DNA packing Figure a 2 nm 10 nm DNA double helix Histone tails His- tones Linker DNA (“string”) Nucleosome (“bad”) Histone H1 (a) Nucleosomes (10-nm fiber) Nucleosome 30 nm (b) 30-nm fiber Higher Levels of DNA Packing The next level of packing Forms the 30-nm chromatin fiber Figure b The 30-nm fiber, in turn Forms looped domains, making up a 300-nm fiber Figure c Protein scaffold 300 nm (c) Looped domains (300-nm fiber) Loops Scaffold In a mitotic chromosome The looped domains themselves coil and fold forming the characteristic metaphase chromosome Figure d 700 nm 1,400 nm (d) Metaphase chromosome In interphase cells Most chromatin is in the highly extended form called euchromatin Concept : Gene expression can be regulated at any stage, but the key step is transcription All organisms Must regulate which genes are expressed at any given time During development of a multicellular organism Its cells undergo a process of specialization in form and function called .

• Sinh học
• Campbells Biology
• Lecture Biology
• Biological sciences
• Biological organization
• Systems biology
• Eukaryotic genomes
• Restoration ecology
• Conservation biology
• Ecosystem dynamics
• The chemical context of life
• Water molecules
• The molecular diversity of life
• Function of macromolecules
• Membrane structure
• Metabolism transforms matter
• Cellular respiration
• Chemical energy of food
• Cell communication
• The cell cycle
• Sexual life cycles
• The gene idea
• Locating genes
• The molecular basis of inheritance
• Genetic information
• Microbial model systems
• DNA technology
• The genetic basis of development
• Darwin’s theory
• The evolution of populations
• The origin of species