Independent: The second group is not given the drug.
Dependent: Dr. Smith wants to examine weather a new drug increases the maze running performance of older rats.
Constants: Dr. Smith teaches two groups of older rats to find a piece of tasty rat chow in the maze.
Answer:
20 million years
Explanation:
If we have a neutral mutation rate of one mutation per 5 million years, then the total of eight mutation between the two different species would be 20 million years. This is because both species will have 4 mutations in those 20 million years, so combined, both by 4, will have 8 mutations between them. So few mutations on so much time will result in two species that are very similar to each other even after 20 million years of evolution, even making them hardly distinguishable, especially if it comes to defining fossil records from them both. A nice example of this are the members of the felidae (cat) family, which are all very closely related, and are almost identical, thus making it extremely hard to distinguish two species of the same or similar size by their fossils.
Answer:
true
Explanation:
Similarly, expression of a human gene in yeast and bacteria allows pharmaceutical companies to produce insulin to treat diabetic patients. In 2020, scientists had their first successful human trial with CRISPR (a genetic engineering technique), to correct a mutant gene that causes sickle cell anemia, a painful and sometimes deadly blood disease.
A sex-linked trait is a trait that is carried by the X chromosomes in females but it is not expressed(the phenotype). Females are only carriers because they have two copies of the X chromosome [one of them carries the trait and the other does not]. Males who inherit one copy of the X chromosome often get the trait (because the trait is in either one copy or the other of the X chromosome) and express it while their Y chromosome would became recessive. Thus, only males express sex-linked traits such as hemophilia or color blindness
