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The disease AIDS is the result of infection by the human immunodeficiency virus (HIV), a retrovirus which has RNA as its genetic material - VCE - SSCE Biology - Question 8 - 2006 - Paper 1
Question 8
The disease AIDS is the result of infection by the human immunodeficiency virus (HIV), a retrovirus which has RNA as its genetic material. a. RNA is a nucleic acid,... show full transcript
Worked Solution & Example Answer:The disease AIDS is the result of infection by the human immunodeficiency virus (HIV), a retrovirus which has RNA as its genetic material - VCE - SSCE Biology - Question 8 - 2006 - Paper 1
Step 1
a. Draw a labelled diagram of a monomer of RNA.
Answer
A monomer of RNA, also known as a nucleotide, consists of three main components:
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Phosphate Group: This is a phosphorus atom bonded to four oxygen atoms. The linkage of the phosphate group to the ribose sugar forms the backbone of the RNA strand.
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Ribose Sugar: This is a five-carbon sugar that plays a critical role in the structure of RNA. It differs from DNA’s deoxyribose by having one additional oxygen atom.
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Nitrogenous Base: There are four possible nitrogenous bases for RNA, which can include adenine (A), uracil (U), cytosine (C), and guanine (G). Each base bonds with the ribose sugar, forming a complete nucleotide.
In a diagram, these components should be linked appropriately. The phosphate should connect to the first carbon of the ribose, and the nitrogenous base should attach to the first carbon on the ribose as well, forming a visual representation of the nucleotide.
Step 2
b. Explain what is happening in the first year after infection with the HIV virus.
Answer
During the first year after HIV infection, the dynamics between T cell concentration and HIV concentration demonstrate a crucial phase of the disease progression. Initially, T cells, which are essential components of the immune system, experience a significant drop due to the viral infection as the HIV virus targets and destroys these cells.
In the early stages of infection, there is often a spike in HIV particles as the virus replicates rapidly, leading to a substantial increase in viral load. This results in a peak in HIV concentration, generally occurring around six months post-infection. Subsequently, T cells begin to recover slightly, but overall, their numbers remain lower than pre-infection levels. This creates a context wherein the immune system is compromised, leaving the individual vulnerable to opportunistic infections.
Step 3
c. In the second to fifth years (inclusive) after infection the patient has swollen lymph nodes. Explain.
Answer
The swelling of lymph nodes during the second to fifth years after HIV infection is primarily related to the immune response as the body attempts to fight against the ongoing HIV infection. Lymph nodes serve as critical sites for immune cell activation and proliferation; thus, they enlarge as T cells, B cells, and other immune components congregate to combat the virus.
Furthermore, this prolonged immune activation can contribute to chronic inflammation and may indicate a progression towards AIDS. Despite the initial drop in T cell counts due to HIV, during this period, the immune system is still trying to control the viral load, which can lead to persistent swelling of the lymph nodes as they remain responsive to the ongoing infection.