MCB181 Chapter 20- Genes and Development
Despite outward differences, eye anatomy—even between the eyes of planarians and humans—is remarkably similar. (T or F)
False
Differentiating cells delete the DNA for genes they do not need. (T or F)
False
Each ligand-receptor pair has a distinct function and is involved in a single cellular process. (T or F)
False
Ectoderm gives rise to cells lining the digestive tract and lungs, as well as liver and pancreas. (T or F)
False
Given the lack of any evolutionarily conserved genes between Drosophila, marine life, and mammals, it is most likely that eyes evolved independently in these organisms. (T or F)
False
If an anchor cell in a C. elegans embryo failed to produce EGF, then all of the three initial progenitor cells would go on to form type I cells, and lateral inhibition will not occur. (T or F)
False
In a normal Drosophila embryo, a gap gene called Krüppel is expressed in the anterior end because it is activated by Hunchback protein, and this region contains a high level of Hunchback. (T or F)
False
Only compound eyes possess opsin, providing evidence that eyes evolved independently in vertebrates and invertebrates. (T or F)
False
The fertilized egg is totipotent, whereas the cells from the inner cell mass, called embryonic stem cells, are pluripotent. Only the embryonic stem cells can give rise to the entire organism. (T or F)
False
The ligand of any ligand-receptor pair is always "free-floating"; ligands are never attached to the cell surface, unlike receptors. (T or F)
False
The majority of receptor-ligand pairs are only involved in cell metabolism; these pairs rarely play a role in cell differentiation. (T or F)
False
The percentage of living animals possessing true eyes that can produce an image is small. (T or F)
False
Cells become differentiated because genes that are not being expressed are deleted. (T or F)
False?
Imagine that a scientist introduced a copy of the human Pax6 gene into a mouse. What would likely happen in this scenario?
The mouse may go on to form an ectopic eye that resembles a mouse eye in shape and structure, given that the genes acting downstream of Pax6 are still "mouse" genes.
A researcher has discovered a new mutant strain of mice where individuals develop two extra eyes—one on each ear. Given the appearance of "extra" eyes, these mice likely carry a gain-of-function mutation in Pax6 (or in a gene acting downstream of Pax6). (T or F)
True
As cells continue differentiating, they increasingly lose their developmental potential and their fate becomes more restricted. (T or F)
True
Both squids and vertebrates have single-lens eyes, but they are very different in their development, anatomy, and physiology. (T or F)
True
Compound eyes consist of hundreds of small lenses arranged on a convex surface. (T or F)
True
Ectoderm gives rise to epithelial cells, pigment cells of skin, and nerve cells in the brain. (T or F)
True
Endoderm gives rise to cells lining the digestive tract and lungs, as well as liver and pancreas.
True
Evolution of the spherical lens improved images as animals evolved. (T or F)
True
Germ layers are sheets of cells that will differentiate into specialized cells. (T or F)
True
Homeotic genes encode very important transcription factors that specify the identity of body parts or segments during development. For example, the development of legs on thoracic segments T1, T2, and T3 and wings on segment T2 is controlled by homeotic genes. (T or F)
True
In the Drosophila embryo, gap genes govern the partitioning of the anterior-posterior gradient into segments. (T or F)
True
Mesoderm gives rise to cells that make up the inner layer of skin, muscle cells, and red blood cells. (T or F)
True
Mutants of Drosophila melanogaster have been used extensively to explore the genetic control of early development, particularly the hierarchical control of development, which means that genes expressed at each stage control the expression of genes that act later. (T or F)
True
Planaria have the simplest eyes, which are basically pit-shaped cells containing photoreceptors. (T or F)
True
Several genes involved in the early stages of development are conserved across many types of organisms. (T or F)
True
The Nobel Prize for Physiology or Medicine was awarded to Christiane Nusslein-Volhard and Eric F. Wieschaus due to their discovery that Drosophila development begins in the maturing oocyte, before fertilization. (T or F)
True
To avoid using controversial embryonic stem cells, scientists have learned to reprogram fully differentiated adult cells and return them to a pluripotent state. (T or F)
True
Zygote:
a fertilized egg
Imagine that a human embryo carries a mutation in the gene encoding the Notch receptor. What will this mutation affect?
bone development in the human embryo heart development in the human embryo nervous system development in the human embryo pancreas development in the human embryo
Transcription factors like Pax6 interact with their target genes by binding short sequences adjacent to the 5' end of a gene sequence called _________________ elements.
cis-regulatory
In vulval development in Caenorhabditis elegans, the progenitor cell nearest to the anchor cell is exposed to the highest concentration of epidermal growth factor and activation of its EGF receptor promotes type I cell differentiation. The type 1 cell then prevents type 1 differentiation in adjacent progenitor cells, a mechanism called _________________ inhibition.
lateral
Oocyte:
the unfertilized egg cell produced by the mother
