B5C

Cell differentiation is critical during embryonic development. The process of cell differentiation results in the production of many types of cells, including germ, somatic, and stem cells. Cell differentiation is most directly regulated by -

• ATP

• DNA

• lipids

• sugars

Researchers Robert Briggs and Thomas King used ultraviolet radiation to destroy the nuclear DNA of frog eggs. Nuclei from adult skin cells and from tadpole-gut epithelial cells were cultured and then injected into eggs that had their nuclei destroyed. The results were tadpoles. Which conclusion is supported by the data from this investigation?

• the DNA information for development was silenced in differentiated cells

• the transplanted DNA functioned as the original nuclear DNA of the egg cell would have

• the DNA from skin cells and epithelial cells was not transcribed

• the transplanted DNA mutated during culturing

As a fertilized egg divides, the cells differentiate because they -

• contain a lipid bilayer

• can clump together

• metabolize sugars rapidly

• have specific genes activated

From a single fertilized ovum undergoing a series of rapid cell divisions, a human infant develops. The embryonic cells become specialized for a variety of functions. Which of these statements best describes how different cell types develop?

• each cell type contains only the active parts of the DNA needed for that cell type

• each cell type has only one chromosome containing the DNA needed for that cell type

• each cell has an identical copy of DNA with enzymes controlling the expression of specific genes, leading to a variety of cells

• each cell has multiple copies of DNA that are affected in different ways by the environment to change the function of the cell at regular intervals

What is the role of mRNA in expressing specialized structures?

• making energy available for cellular activities

• creating bonds to form biomolecules

• producing sugars that assist with replication

• providing information to form proteins