The Human Immunodeficiency Virus, HIV, is a retrovirus that contains RNA as the genetic material. Scientists believe that the chimpanzee version of the immunodeficiency virus (called Simian Immunodeficiency Virus or SIV) was the original source of HIV infection in humans.
It is theorized that SIV was transmitted to humans and mutated into HIV when humans in Africa hunted chimpanzees for meat and exposed themselves to the infected blood. The mutation rate in retroviruses, including SIV and HIV, is much higher than it is among DNA viruses.
The most likely explanation for this is that

Q. The enzyme that helps human immunodeficiency virus (HIV) to integrate its own DNA into a host cell's genome is

Q. Which of the following is used by Human immunodeficiency virus (HIV) to integrate its own DNA into a host cell's genome?

Q. There is great genetic variation among types of viruses, and every species on Earth has its own unique category of viruses that are able to infect it. Furthermore, within a single species, viruses exhibit specificity for unique cell types.
For example, Human Immunodeficiency Virus (HIV) infects T-helper immune cells and Human Papilloma Virus (HPV) primarily infects the squamous epithelial cells that line the outside (skin) and inside of body cavities. The image above illustrates the basic structure of an animal virus:
Which of the following best explains the specificity of viral infection?

Q. Name the cells HIV (Human Immunodeficiency Virus) gains entry into after infecting the human body. Explain the events that occur in these cells. [2]

Q. The CCR5 gene codes for a protein on the surface of T cells. The CCR5 protein is used by Human Immunodeficiency Virus (HIV) to enter T cells, which ultimately leads to Acquired Immunodeficiency Syndrome (AIDS). AIDS was first reported in the European population in the early 1980s.
About 3000 years ago in Central-Western Europe a mutation occurred that prevents normal expression of the surface protein. People with one copy of the mutated allele have delayed onset of AIDS. Homozygotes for the mutation are resistant to HIV infection.
Evidence suggests that the trait also protects individuals from the smallpox virus. Smallpox was common in the European population from the Middle Ages until the early 1900s, causing several major epidemics with high death rates. It was eradicated through widespread vaccination.
The frequency of the allele is 16% in Scandinavia and 4% in Greece. What are the expected frequencies of HIV-resistant individuals in each population and which evolutionary explanation for the difference is most plausible?