20. Development

What is apoptosis?

a. An experimental technique used to kill specific cells

b. Programmed cell death that is required for normal development

c. A pathological condition observed only in damaged or diseased organisms

d. A developmental mechanism unique to the roundworm C. elegans

Which of the following occurs when a covalent bond forms?

a. Electrons in valence shells are transferred from one atom to another.

b. Electrons in valence shells are shared between atoms.

c. Partial charges on polar molecules interact.

d. Nonpolar molecules are pushed together.by surrounding water molecules.

In adult animals, ___________ are a source of undifferentiated cells that can divide to produce cells that can specialize.

What does it mean to say that a characteristic is heritable?

a. The characteristic evolves.

b. The characteristic can be passed on to offspring.

c. The characteristic is advantageous to the organism.

d. The characteristic does not vary in the population.

Could both the food competition hypothesis and the sexual competition hypothesis explain why giraffes have long necks? Why or why not?

Cell differentiation always involves

a. Transcription of the myoD gene.

b. The movement of cells.

c. The production of tissue-specific proteins.

d. The selective loss of certain genes from the genome.

Which of the following is a valid difference between embryonic stem cells and the stem cells found in adult tissues?

a. In laboratory culture, only adult stem cells are immortal.

b. In nature, only embryonic stem cells give rise to all the different types of cells in the organism.

c. Only adult stem cells can differentiate in culture.

d. Embryonic stem cells are generally more difficult to grow in culture than adult stem cells.

A friend is interested in isolating genes that are expressed solely in liver cells but only has access to skin cells. She asks you for advice on whether to start her studies. What will you say?

What did Linnaeus' system of naming organisms ensure?

a. Two different organisms never end up with the same genus and species name.

b. Two different organisms have the same genus and species name if they are closely related.

c. The genus name is different for closely related species.

d. The species name is the same for each organism in a genus.

Scientists have recently developed a process by which a skin cell from a human can be triggered to develop into a human heart muscle cell. This is possible because ________.

a. Most cells in the human body contain the genetic instructions for making all types of human cells.

b. A skin cell is produced when all genes in the cell are expressed; turning off some genes in the cell results in a heart cell.

c. Scientists can add new genes to old cells to make them take different forms.

d. A skin cell expresses only recessive alleles, so it can be triggered to produce dominant heart cell alleles.

e. It is easy to mutate the genes in skin cells to produce the alleles required for other cell types.

A genetic change that caused a certain Hox gene to be expressed along the tip of a vertebrate limb bud instead of farther back helped make possible the evolution of the tetrapod limb. This type of change is illustrative of

a. The influence of environment on development.

b. Paedomorphosis.

c. A change in a developmental gene or in its regulation that altered the spatial organization of body parts.

d. Heterochrony.