Which gene program is described correctly?
A.
Cell division is the process whereby identical cells begin to specialize into specific cell types.
B.
Signal induction identifies important body axes such as anterior-posterior and dorsal-ventral.
C.
Differentiation increases the number of cells, so an organism can grow larger.
D.
Morphogenesis is the process whereby cells identify where they are in three-dimensional space.
Signal transduction pathways are important mechanisms for cell-to-cell communication in multicellular organisms. How do the target cells typically respond when they receive signals from neighboring cells during very early stages of embryo development?
A.
The target cells move to one of the poles to establish the anterior-posterior body axis.
B.
The target cells undergo changes in gene expression, sending them down a specific developmental path.
C.
The target cells stop dividing so the neighboring cells have time to get to the same stage of development.
D.
The target cells activate a collection of miRNAs to accelerate transcription and cell division.
Master regulatory genes play critical roles in development. Predict the MOST likely fate of a fly embryo where master regulatory genes were nonfunctional due to mutation.
A.
Cell division would stop, and the embryo would halt development.
B.
The embryo would be a collection of undifferentiated cells because they never get the message that will send them down a determination pathway.
C.
The embryo would be a combination of differentiated and undifferentiated cells because, even in the absence of a functional master regulatory gene, some cells will differentiate on their own.
D.
The embryo would continue to develop, but there is a high probability that some limbs may end up in the wrong place in the adult.
When in fruit fly development does axes development begin?
A.
in the unfertilized egg stage when maternal effect genes deposit mRNA and proteins in specific locations
B.
in the early embryo stage when induction signals between neighboring cells identify where the cells are in three-dimensional space
C.
in the larval stage when body segments appear, and pattern formation is evident
D.
in the pupal stage when a gradient of morphogens is established
The p53 gene was discovered in 1979, but it was not clear whether the gene functioned as an oncogene or a tumor-suppressor gene. Several years later, researchers showed that both p53 alleles are inactivated in some mouse cancers. This evidence suggests
A.
the p53 gene is an oncogene because inactivated alleles would produce mutated signal transduction proteins that would result in stimulating cell division.
B.
the p53 gene is an oncogene because the cell would overproduce transcription factors to compensate for the inactive alleles, resulting in increased cell division.
C.
the p53 gene is a tumor-suppressor gene because inactivated alleles indicate a loss of protein function which allowed the cancer to develop.
D.
the p53 gene is a tumor-suppressor gene because the cell would produce too few transcription factors for gene activation, resulting in decreased cell division.
A. Cell division is the process whereby identical cells begin to specialize into specific cell types.
B. The target cells undergo changes in gene expression, sending them down a specific developmental path.
B. The embryo would be a collection of undifferentiated cells because they never get the message that will send them down a determination pathway.
A. in the unfertilized egg stage when maternal effect genes deposit mRNA and proteins in specific locations
C. the p53 gene is a tumor-suppressor gene because inactivated alleles indicate a loss of protein function which allowed the cancer to develop.