prettypink1881

prettypink1881 I'm pretty sure a stimulus is anything internal or external that may/can trigger a response wheras an antecedent is exclusive to operant conditioning and creates the environment for the following behaviour (for example the antecedent could be a parent saying the dishes need to be done, the behaviour would be the child doing the dishes and the consequence would be praise). I hope that makes sense/is helpful

prettypink1881 yes you don't need to know about it in detail. From memory, VCAA usually focuses on bacteria being extracellular, but many would still initiate the cell-mediated response because they can invade host cells. In reality, biology is a lot more complex haha. However, if you were asked to explain the third line of defence in relation to bacteria, I would usually just stick with the humoral response for sake of time and the marking scheme since all bacteria will definitely initiate this response.

Taaaa76 the same adaptive immune response that involves macrophages engulfing foreign antigens/cells and then oresenting to helper T cells etc etc

prettypink1881 The stem of that part of the question says the probes attach only to complementary sequences on particular viruses. So if a probe didn't exist with that particular complementary sequence then it wouldn't work because the probes are required for RT-PCR. I think?

prettypink1881 Hi,
So the tetracycline resistance gene gives the bacteria resistance to the antibiotic tetracycline, allowing the bacteria to grow in an environment with tetracycline. The beta-galactosidase gene, which synthesises beta-galactosidase, once hydrolysed in a substance called X-gal, breaks that beta-galactosidase into galactosidase and indole. This indole compound is what is responsible for bacteriaeria turning blue.

HKS This is the traditional way of manufacturing human insulin in the 1980s. If the question does not specify a year, like 2020, you would talk about insulin A and B. It was just in this specific context of how they do it in 2020, in which they do it all in one bacteria.

prettypink1881 Sorry for the late reply.

But the beta galactosidase gene is added after the bacteria with the recombinant plasmids have been identified.
Essentially, once the bacteria are exposed to ampicillin and then tetracycline, then the recombinant bacteria have been identified, these bacteria are opened up again and there plasmids are removed once again. EcoRI (restriction enzyme) cuts upstream the insulin gene, and EcoRI also cuts the beta galactosidase gene. The gene and plasmid are mixed together and a new recombinant plasmid will form as they have complementary overhangs created by EcoRI. The 'recombinant plasmid with the beta galactosidase gene' contain the tetracycline, ampicillin and beta galactosidase gene. Originally, the recombinant plasmid only had the tetracycline and ampicillin gene.

prettypink1881
Thanks so much I really appreciate it!

prettypink1881

That's a relief. Thanks for letting me know so quickly

chimichurri I agree with prettypink1881, but also, during a viral infection, usually both your cell-mediated and humoral responses occur. Cell-mediated response targets infected cells, but the humoral response will also be initiated because the cells lyse and release more viral particles into the extracellular environment. Viruses can be extracellular and intracellular, so both responses would be initiated. With a vaccines, both would be usually be stimulated, as mentioned in the answer by VCAA (they state that B and T memory cells are produced). A live attenuated virus in the vaccine will replicate using the person's cells but at a very low level (not enough to cause proper disease), meaning a cell-mediated response is necessary. However, some of virus won't be inside cells and will be in the blood, requiring the humoral response. Both responses almost always work together in the third line of defence (since almost all pathogens will be able to be extracellular and intracellular in some way, and there a exceptions to these processes anyway since biology is kinda like that ahaha).

Question 4a in the VCAA 2021 Exam is confusing me a bit and I was wondering if someone could help

The question:
Varicella (chickenpox) is a highly contagious disease caused by the varicella zoster virus. A live, attenuated
varicella zoster virus vaccine is recommended for children at age 18 months. In Australia, this vaccine is
provided free of charge under the National Immunisation Program.
a. Once the varicella zoster virus vaccine is injected into the arm of a child, an immune response occurs.
Summarise the immune response that occurs within the child to result in long-term protection from
chickenpox. [5 marks]

The VCAA Marker's Guide:
A suitable answer was that the vaccine is taken up by, for example, macrophages and antigen presented on the surface of the cell. The antigen presenting cell moves into the lymphatic system and is taken to the lymph node. Helper T cell stimulates naïve B cells. Each B cell divides to produce plasma cells, which produce specific antibodies. B memory and or T memory cells are produced for long-term immunity
This was very well answered. Many students presented clear logical answers and demonstrated a sound understanding of how long-term immunity is achieved.

I was wondering why we are expected to talk about B cells and antibodies when this question is a virus? As viruses are intracellular pathogens shouldn't a response to this question focus on the cell-mediated response and thus T cells?