Human Development And STEM Cell Quiz

Stem cells differentiate due to the presence of growth factors. Growth factors are signaling molecules that stimulate cell division and differentiation. They play a crucial role in regulating the fate of stem cells by activating specific signaling pathways within the cells. These pathways then trigger the expression of specific genes that lead to cellular differentiation. Growth factors can either promote or inhibit differentiation depending on the specific factors present in the cellular microenvironment.

A stem cell is not specialized because it has the ability to differentiate into various types of cells in the body. This means that it can develop into specialized cells such as nerve cells, muscle cells, or blood cells. In contrast, sperm cells are specialized for reproduction, and bone cells are specialized for supporting and maintaining the structure of the bones.

The gastrula stage of development contains the three germ layers. During gastrulation, the blastula undergoes a process where the cells rearrange and form three distinct layers: the ectoderm, mesoderm, and endoderm. These germ layers give rise to different tissues and organs in the developing organism. Therefore, the correct answer is gastrula.

The statement "They reside in the body throughout life" is false because stem cells from the mesoderm layer do not remain in the body throughout life. These stem cells are found during embryonic development and play a crucial role in the formation of various types of tissues, including blood cells. However, they are not considered embryonic stem cells, which are derived from the inner cell mass of the embryo. Mesoderm stem cells are multipotent, meaning they have the ability to differentiate into multiple cell types, but they are not present in the body throughout an individual's entire life.

A zygote is formed when a sperm cell fertilizes an egg cell. Each sperm and egg cell contains 23 chromosomes, so when they combine, the zygote will have a total of 46 chromosomes. This is because humans have 23 pairs of chromosomes, with one chromosome from each pair coming from the mother and the other from the father. Therefore, the correct answer is 46, not 2.