First, it is necessary that this scientist decide on what point of the Cretaceous period he wants to study. Among several points he may want to study the evolution of microorganisms of that time, the life of a dinosaur species, or the evolution of dinosaurs, the flora that was established during this period, among others. This is the phase of the scientific method called Observation.
After that, he must enter the phase called "Elaboration of hypotheses" where he will raise questions about the point he decided to study. "How many flower species existed in that period?", "How many of these flowers can we observe today?" among others.
After that, he will enter the phase called "Experimentation", where he will establish a type of experiment and all the experimental factors and variables that will allow the hypotheses to be answered.
After the experiment he will collect the data that will be analyzed and that will give results that will answer the hypotheses previously established. This is the phase called "Analysis of the results".
At that moment, he will be able to reach the last phase of the scientific method, the phase called "conclusion", where he will show the conclusions that the experiment allowed to be established.
Answer:
The correct answer is ''undergo irreversible repression.''
Explanation:
The morphological and physiological transformation of meristematic cells into adult or differentiated tissues constitutes the process of cell differentiation. This, and the consequent specialization of the cell, bring about the division of labor, forming cells with specific functions. Differentiation occurs by differential activation of some genes and repression of others. Depending on the position it occupies, each cell receives certain stimuli to develop the corresponding activities. During the differentiation process, cells undergo a series of changes in their characteristics and there is a readjustment in their mutual relationships.Different molecular factors initiate and drive the programming / reprogramming of cell fate through the modulation of specific genomic and epigenomic patterns, which regulate the expression of activator / repressor genes of the main fundamental and specialized cellular processes. Thus, the differentiated cell will express certain genes and acquire certain functions.Adult stem cells are responsible for maintaining the different types of specialized cells that make up the body. Asymmetric cell division in stem cells has emerged as one of the main physiological mechanisms that regulate the number of cells and their diversity to maintain tissue homeostasis. A large number of molecules, generically called determinants of cell fate, participate in the regulation of asymmetric division. Asymmetric division of somatic stem cells produces both a stem cell and a progenitor. The initial progenitor cells, through new cycles of asymmetric cell division, finally reach their terminal state of cell differentiation, due to changes in intracellular and extracellular (environmental) signaling. After cells leave their mother state and begin to differentiate, they make exclusive selections for phenotypic pathways through secondary genomic / epigenomic modifications, mainly to different types and gradients of transcription factors (physiological programming of cell differentiation). This leads, for example, to activation of specialized biosynthetic pathways, remodeling of the cytoskeleton, and repression of cell proliferation signaling. The expression of genes is regulated mainly at the level of their transcription. Transcription factors correspond to proteins with the ability to interact with specific DNA sequences and trigger their transcriptional activity. Most transcriptional factors contain different domains that participate in different aspects of protein function; they generally contain two domains: a domain that binds to specific DNA sequences and an activation domain that regulates transcription by interacting with other proteins. In the regulation of gene transcription, in addition to transcription factors, coactivating and corepressor molecules participate, which bind to them, modifying their activity in a positive or negative sense. Each cell type has a characteristic pattern of gene transcription, which is determined by the binding of combinations of transcription factors to the regulatory regions of a gene.
Density = Mass divided by Volume, or d = m/v.
So, replace the m and v with the amounts given:
d = 0.5.
Density = Mass / Volume
