Answer:
dyes used in negative staining have an. acidic chromagen (negatively charged chromophore) Examples of negative stains. NIgrosin and eosin. heat fixing smears can.
When a biologist counts the number of zebras in a population each year and notices an increase in the zebra population, this would be an example "of <span>observation"</span>
Answer:
PFFT this might help? sorry if not mate
Explanation:
Cell cycle checkpoint controls play a major role in preventing the development of cancer [see Sherr, 1994, for a more detailed discussion]. Major checkpoints occur at the G1 to S phase transition and at the G2 to M phase transitions. Cancer is a genetic disease that arises from defects in growth-promoting oncogenes and growth-suppressing tumor suppressor genes. The p53 tumor suppressor protein plays a role in both the G1/S phase and G2/M phase checkpoints. The mechanism for this activity at the G1/S phase checkpoint is well understood, but its mechanism of action at the G2/M phase checkpoint remains to be elucidated. The p53 protein is thought to prevent chromosomal replication specifically during the cell cycle if DNA damage is present. In addition, p53 can induce a type of programmed cell death, or apoptosis, under certain circumstances. The general goal of p53 appears to be the prevention of cell propagation if mutations are present. The p53 protein acts as a transcription factor by binding to certain specific genes and regulating their expression. One of these, WAF1 or Cip1, is activated by p53 and is an essential downstream mediator of p53-dependent G1/S phase checkpoint control. The function of p53 can be suppressed by another gene, MDM2, which is overexpressed in certain tumorigenic mouse cells and binds to p53 protein, thus inhibiting its transcriptional activation function. Other cellular proteins have been found to bind to p53, but the significance of the associations is not completely understood in all cases. The large number of human cancers in which the p53 gene is altered makes this gene a good candidate for cancer screening approaches.
Answer:
b) At equilibrium, the species composition of an island will not change.
Explanation:
The Theory of Island Biogeography written by Robert H. MacArthur and Edward O. Wilson (1967) is an essential book for any professional working in biogeography, biodiversity, ecology, conservation and related fields. The theory of island biogeography states that species diversity on islands tends to approach a dynamic equilibrium due to the balance between colonization (inmigration), speciation and extinction. At equilibrium, the species composition of an island will change, precisely at the time that immigration and extinction processes maintain the number of species in a dynamic equilibrium, thereby maintaining species diversity. In this case, the colonization rate represents a function of distance to the continent (or other islands), the extinction rate is a function of the size of the island and habitat heterogeneity, and speciation is a function of time. This book also contains a series of useful considerations: 1-the number of species in an area is directly associated with the size of the area; 2-large islands support more diverse communities than small islands; 3-the viability of populations on island systems can be considered as a function of the island size and its proximity to the mainland (or other islands); and 4- when a habitat is lost the remaining fragmented area may lose some of its important species.
