• YACs and the Common Mouse
• Packing DNA into Small Spaces
• The Bacterial Chromosome
• The Eukaryotic Chromosome
Chromotin Structure
Centromere Structure
Telomere Structure
• Variation in Eukaryotic DNA
Sequences
Denaturation and Renaturation
of DNA
Renaturation Reactions and C0t
Curves
Types of DNA sequence in
Eukaryotes
• The Nature of Transposable
Elements
General Characteristics of
Transposable Elements
Transposition
Mechanisms of Transposition
The Mutagenic Effects of
Transposition
The Regulation of Transposition
• The Structure of Transposable
Elements
Transposable Elements in Bacteria
Transposable Elements in Eukaryotes
YACs and the Common Mouse
The common house mouse, Mus musculus, is among the
oldest and most valuable subjects for genetic study. It’s an
excellent genetic organism—small, prolific, and easy to
keep, with a short generation time (about 3 months). It tolerates
inbreeding well; so a large number of inbred strains
have been developed through the years. Finally, being a
mammal, the mouse is genetically and physiologically more
similar to humans than are other organisms used in genetics
studies, such as bacteria, yeast, corn, and fruit flies.
Powerful tools of molecular biology have enhanced the
mouse’s role in probing fundamental questions of heredity.
New and altered genes can be added to the mouse genome
by injecting DNA directly into embryos that are implanted
into surrogate mothers. The resulting transgenic mice can
be bred to produce offspring carrying the new genes.
Today, it is possible to introduce not just individual
genes, but entire chromosomes into mouse cells. In 1983, the
first artificial chromosomes, made of parts culled from yeast
and protozoans, were created for studying chromosome
structure and segregation. In 1987, David Burke and
Maynard Olson (at Washington University, St. Louis) used
yeast to create much larger artificial chromosomes called
yeast artificial chromosomes or YACs. Each YAC includes the
three essential elements of a chromosome: a centromere, a
pair of telomeres, and an origin of replication. These elements
ensure that artificial chromosomes will segregate in