the age of fossils can sometimes be determined by radiometric dating, which is based on the constant rate of decay of radioactive isotopes. the time required for half of a radioactive isotope to decay is called the half-life of that isotope. for example, the isotope carbon-14 has a half-life of 5,730 years.

The gene that causes sickle-cell disease is present in a higher percentage of residents of sub-saharan africa than among those of african descent living in the united states. even though this gene causes sickle-cell disease, it also provides some protection from malaria, a serious disease that is widespread in sub-saharan africa but absent in the united states. discuss an evolutionary process that could account for the different percentages of the sickle-cell gene among residents of the two regions.

Protein synthesis actually begins in the nucleus when transcribes a single gene on the dna molecule is copied. the process of copying this gene is called this copy is known as and contains the protein building instructions. this copy is sent out into the cytoplasm to the part of the cell known as the the of the ribosome will join together to form a functional ribosome when they attach to the mrna. as the mrna moves through the ribosome, the message is read by transfer rna brings the correct back to the ribosome. the amino acids are placed in the correct order and are hitched together by

One of the newest applications of cell technology is called cybrid embryos. this process involves replacing the nuclear material of an animal cell with human nuclear material. how might this process affect public policies about research by using stem cells? the same policies and concerns about the use of human embryonic stem cells would most likely apply. the embryos would most likely be treated like traditional animal embryos and regulated accordingly. the process of forming cybrid embryos would most likely be banned by government regulators. the embryos would be treated as regular cells because they are not fully human in origin.