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:
Of the 23 pairs of chromosomes in any normal human cell, the first 22 pairs provide directions for an individual's body and brain development. Scientists now estimate that about half of a person's personality traits and cognitive abilities can be traced to genetic influence and that psychological disorders arise from the interactions of many genes.
Explanation:
Chromosomes are small molecules that have the ability to carry all the genetic information needed to form a living being. These chromosomes are donated by an individual's parents and are used to form 23 pairs that determine all the internal and external characteristics of an organism. Among these 23 pairs, one pair will be responsible for determining the individual's gender, and the other 22 pairs will be responsible for the instructions that will make up the entire body and brain of the individual. Many scientists believe that chromosomes are responsible for even a part of a person's personality traits and that the genes they carry are directly related to the existence of psychological disorders.
Mass and distance affect the gravitational force.
Answer:
The strengths of Brønsted-Lowry acids and bases in aqueous solutions can be determined by their acid or base ionization constants. Stronger acids form weaker conjugate bases, and weaker acids form stronger conjugate bases.
Explanation:
During meiosis one cell? divides twice to form four daughter cells. These four daughter cells only have half the number of chromosomes? of the parent cell – they are haploid. Meiosis produces our sex cells or gametes? (eggs in females and sperm in males).
