Aa x Aa= AA, Aa, aa. 2 phenotypes
The human immunodeficiency virus (HIV) that causes the disease known as aids selectively infects helper T cells (CD4+).
This retrovirus also infects macrophages and dendritic cells. When CD4+ T cell numbers decrease below a critical level (due to the killing of this cells with different mechanisms), cell-mediated immunity is lost. As a result, the body becomes progressively more susceptible to infections, leading to the development of AIDS.
<span> HIV can be transmitted only via body fluids like blood, semen, pre-seminal fluid, rectal fluids, vaginal fluids, and breast milk, which means that people usually get or transmit HIV through sexual behaviours and use of the needle. For HIV infection, these fluids must come in direct contact with a mucous membrane or damaged tissue. Another way is to be directly injected into the bloodstream (from a needle for example).</span>
Answer:
Both processes generate energy for cell use.
The products of one process are used as reactants by the other process.The products of one process are used as reactants by the other process.
Explanation:
Photosynthesis is the process by which glucose is formed in plants with the aid of light energy and chlorophyll. Cellular respiration is the breakdown of glucose to release energy, water and carbon dioxide. The end products of respiration are used in photosynthesis. Glucose formed from photosynthesis is used in respiration as a reactant.
The statement which explains why muscle cells and skin cells do not look and act the same is this: THE GENES IN EACH TYPE OF CELL ARE BEEN EXPRESSED DIFFERENTLY.
All the cells in human's body has the same set of genes, this is because, all the cells in the body originated from a single fertilized egg. Even though all the cells in the body has the same origin, they are different from one another because, the cells use the same set of genes differently.
