1. THE ORGANIZATION AND CONTROL OF EUKARYOTIC GENOMES
CHAPTER 19
THE ORGANIZATION AND CONTROL OF EUKARYOTIC GENOMES

2. I. THE STRUCTURE OF CHROMATIN
CHROMATIN STRUCTURE IS BASED ON SUCCESSIVE LEVELS OF DNA PACKING MOSTLY OF DNA AND HISTONE PROTEINS THAT BIND TO THE DNA TO FORM NUCLEOSOMES, THE MOST BASIC UNITS OF DNA PACKING.
NUCLEOSOMES: DNA-HISTONE COMPLEX
FOLDING LEADS ULTIMATELY TO HIGHLY COMPACTED HETEROCHROMATIN
HETEROCHROMATIN: AREAS WHERE THE NUCLEOSOMES ARE MORE TIGHTLY COMPACTED, AND WHERE DNA IS INACTIVE
MOST CHROMATIN IS IN A HIGHLY EXTENDED FORM, EUCHROMATIN
EUCHROMATIN: REGIONS WHERE THE DNA IS LOOSELY BOUND TO NUCLEOSOMES (DNA IS ACTIVELY BEING TRANSCRIBED)

4. II. GENOME ORGANIZATION AT THE DNA LEVEL
A. REPETITIVE DNA AND OTHER NONCODING SEQUENCES ACCOUNT FOR MUCH OF A EUKARYOTIC GENOME
SEQUENCES OF UP TO 10 NUCLEOTIDE PAIRS TANDEMLY REPEATED THOUSANDS OF TIMES ARE ESPECIALLY PROMINENT IN THE DNA OF CENTROMERES AND TELOMERES
THE UNITS OF INTERSPERSED REPETITIVE DNA ARE TYPICALLY LONGER, AND MOST MAY BE TRANSPOSONS OR RETROTRANSPOSONS

5. III. GENE AMPLIFICATION, LOSS, OR REARRANGEMENT CAN ALTER A CELL’S GENOME
THE CELLS OF SOME SPECIES SELECTIVELY LOSE ENTIRE CHROMOSOMES OR PARTS OF CHROMOSOMES IN CERTAIN CELLS.
REARRANGEMENTS OF DNA IN A SOMATIC CELL BY TRANSPOSONS OR RETROTRANSPOSONS CAN ALTER THE CELL’S GENOME IN WAYS THAT AFFECT THE GENE EXPRESSION.