Ch 23: Broad Patterns of Evolution

Question 1

Figure 23.20
Changes in sequence of Hox genes can change body plan.
What are Hox genes?

Answer 1

Genes that regulate development of posterior-anterior axes and body segments.

Question 2

To examine the workings of this gene, researchers cloned the Ubx gene from an insect, the fruit fly Drosophila, and from a crustacean, the brine shrimp Artemia. Next, they genetically engineered fruit fly embryos to express either the Drosophila Ubx gene or the Artemia Ubx gene throughout their bodies. The Drosophila gene suppressed 100% of the limbs in the embryos, as expected, whereas the Artemia gene suppressed only 15%.

Question 3

While a change in the nucleotide sequence of a gene may affect its function wherever the gene is expressed, changes in the regulation of gene expression can be limited to one cell type (see Concept 16.1). Thus, a change in the ________ of a developmental gene may have fewer harmful side effects than a change to the sequence of the gene. This reasoning has prompted researchers to suggest that changes in the form of organisms may often be caused by mutations that affect the regulation of developmental genes—not their __________.

Answer 3

regulation

sequences

Question 4

What are homeotic genes?

Answer 4

Genes that regulate development of anatomical structures.