chapter 21

• The application of genetic analysis and DNA technology to the study of development has brought about a revolution in our understanding of how a complex multicellular organism develops from a single cell.
  • In 1995, Swiss researchers identified a gene that functions as a master switch to trigger the development of the eye in Drosophila.
    • A similar gene triggers eye development in mammals.
  • Developmental biologists are discovering remarkable similarities in the mechanisms that shape diverse organisms.
• While geneticists were advancing from Mendel’s laws to an understanding of the molecular basis of inheritance, developmental biologists were focusing on embryology.
  • Embryology is the study of the stages of development leading from fertilized egg to fully formed organism.
• In recent years, the concepts and tools of molecular genetics have reached a point where a real synthesis of genetics and developmental biology has been possible.
• When the primary research goal is to understand broad biological principles, the organism chosen for study is called a model organism.
  • Researchers select model organisms that are representative of a larger group, suitable for the questions under investigation, and easy to grow in the lab.
• For study of the connections between genes and development, suitable model organisms have short generation times and small genomes that are suitable for genetic analysis.
  • Model organisms used in developmental genetics include the fruit fly Drosophila melanogaster, the nematode Caenorhabditis elegans, the mouse Mus musculus, the zebra fish Danio rerio, and the plant Arabidopsis thaliana.

Figure 21.1 Types of DNA sequences in the human genome.

The pie chart in Figure 21.1 represents the relative frequencies of the following in the human genome:

I. repetitive DNA unrelated to transposons
II. repetitive DNA that includes transposons
III. unique noncoding DNA
IV. introns and regulatory sequences
V. exons

Which region is occupied by exons only (V)?

A) A
B) B
C) C
D) D
E) E

Which region includes Alu elements and LI sequences?

A) A
B) B
C) C
D) D
E) E