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August 12, 2020, 11:10:56 am

Author Topic: Answer a biology question!  (Read 2344 times)  Share 

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laura_

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Re: Answer a biology question!
« Reply #15 on: January 22, 2020, 08:10:58 am »
+5
In forests, short plants that grow low to the ground under the shade of taller plants tend to develop leaves with much larger surface areas than plants in direct sunlight.
a) Explain the evolutionary advantage of larger leaves for these plants

b) A low growing plant species possessing small leaves was introduced to a forest environment where it receives little direct sunlight. Explain the process of natural selection that may occur to this introduced plant species to result in the development of larger leaves over time.
a) It is advantageous for these plants to have larger leaves as they are sheltered from a lot of direct sunlight due to the shelter from other plants meaning that it is difficult for them to get the amount of sunlight that they need to successfully fuel photosynthesis and thus create energy. Larger leaves provide a larger surface area for sunlight to reach and thus larger opportunities for photosynthesis

b) The plant with small leaves receiving minimal sunlight due to its location would struggle to photosynthesis the desired amount and thus would not have sufficient energy. Over generations, plants of this species with slightly larger leaves would be more likely to survive (due to natural selection) and thus more likely to reproduce meaning that gradually this species would come to have larger leaves.

Describe the role of DNA polymerase. (2)
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Chocolatemilkshake

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Re: Answer a biology question!
« Reply #16 on: January 22, 2020, 10:42:07 am »
+7
Describe the role of DNA polymerase. (2)

DNA polymerase is an enzyme that plays an important role in the replication of DNA strands. Its main role is to catalyse the joining together (via condensation polymerisation) of DNA nucleotides (that are complementary to the original DNA strand) in a 3 to 5 prime direction, thereby leading to the formation of another DNA molecule.

And a question for you  ;)
Alex is playing a game on a field of grass and rolls on the grass to reach the ball. He comes home with a mild rash on his legs. Throughout the month, he returns multiple times to play on the same field of grass and every time he comes home with a more severe version of the initial rash.
a) Explain how Alex first became sensitised to the grass allergen. (3)
b) Why does Alex's rash get worse each time he comes in contact with the grass? (2)
« Last Edit: January 22, 2020, 10:43:50 am by Chocolatemilkshake »
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whys

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Re: Answer a biology question!
« Reply #17 on: July 30, 2020, 03:43:03 pm »
+4
And a question for you  ;)
Alex is playing a game on a field of grass and rolls on the grass to reach the ball. He comes home with a mild rash on his legs. Throughout the month, he returns multiple times to play on the same field of grass and every time he comes home with a more severe version of the initial rash.
a) Explain how Alex first became sensitised to the grass allergen. (3)
b) Why does Alex's rash get worse each time he comes in contact with the grass? (2)
a) The grass molecules would enter Alex's body, which would recognise it as a foreign antigen and launch an adaptive immune response. Specific T-helper cells recognise the foreign grass antigen and release cytokines, which stimulate the matching naive B cell to become active and proliferate into plasma cells and memory B cells. These plasma cells will produce specific IgE antibodies that bind to the surface of mast cells, priming the mast cells to recognise the allergen the next time the same grass molecule antigens enter the body through their IgE antibody receptors. During sensitisation, Alex's body will not experience an allergic response.

b) Subsequent exposure to the same grass allergen when Alex goes to play on the same field will cause more IgE antibodies to be released and attach to mast cells. The increased number of IgE antibody receptors on mast cells mean more of them will recognise the grass allergen and release histamine. Histamine will cause vasodilation and increased blood flow to the area, as well as heat, swelling and rashes. As Alex continues to visit the same field, the allergic response will become worse each time, causing his rash to also increase in severity.
(please correct me if I'm wrong, especially for part b), as I wasn't too sure!)

Ella was completing PCR on a segment of DNA in order to use it for subsequent testing. The DNA segment she wants to amplify has the following code:
T T A C A T G A C G T C A

a) What is the complementary sequence to this code? (1 mark)
b) Explain the steps Ella will need to go through in order to successfully complete PCR. Ensure you reference the temperatures and inputs of each step. (4 marks)
c) This DNA segment is a part of a group of linked genes found in bacteria such as E. coli, and is a segment of the lac operon. Explain what occurs when lactose is abundant and glucose is not in terms of gene expression, in reference to the lac operon. (3 marks)
« Last Edit: July 30, 2020, 03:59:37 pm by whys »

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Re: Answer a biology question!
« Reply #18 on: July 30, 2020, 06:00:37 pm »
+3

Ella was completing PCR on a segment of DNA in order to use it for subsequent testing. The DNA segment she wants to amplify has the following code:
T T A C A T G A C G T C A

a) What is the complementary sequence to this code? (1 mark)
b) Explain the steps Ella will need to go through in order to successfully complete PCR. Ensure you reference the temperatures and inputs of each step. (4 marks)
c) This DNA segment is a part of a group of linked genes found in bacteria such as E. coli, and is a segment of the lac operon. Explain what occurs when lactose is abundant and glucose is not in terms of gene expression, in reference to the lac operon. (3 marks)

a) AATGTACTGCAGT

b)
- Ella would need to isolate the DNA segment from the rest of the DNA
- Heat the solution containing the DNA segment to 92ºC, denaturing DNA to separate the DNA into two single strands of DNA.
- Cool the solution to 55ºC and add primers which would attach to complementary DNA sequence.
- Heat the solution to 72ºC and add Taq Polymerase. This would result in the production of copies of the DNA segment.
- The process is repeated multiple times to amplify the DNA segment to the required amount.

c)
- The lac operon is an inducible operon. When lactose is present it binds to the allosteric site of the repressor protein.
- Resulting in a conformation change in the repressor protein, the shape of the active site is altered. Thus, it is unable to bind to the operator region.
- Hence, DNA polymerase is able to bind to the promoter region of the lac operon and transcribe the structural proteins. Therefore, gene expression occurs when lactose is present.

Here’s a few questions for you!  8)

Imagine that we are living in a pandemic, and a nasty virus that is highly virulent is spreading through the globe. You are a virologist who is trying to find a vaccine for this virus – known as coronavirus. A different strain of coronavirus has previously infected the world.

a)   Why would a vaccine be effective in this situation (hint: herd immunity) and how would a vaccine against coronavirus work? (4 marks)
b)   Which kind of drugs will be effective against the virus? Give an example of how a drug might work (2 marks)
c)   Describe the process by which this drug can be produced? (hint: Rational Drug Design) (3 marks)
d)   What are strategies (other than lockdown, wearing masks and washing your hands) can the government introduce to deal with limiting the spread of this contagious virus? (2 marks)
e)   From world renowned scientists, we have heard that a vaccine that acts against this virus can be developed within a year or two. Whereas vaccines for other viruses have taken at least 6 to 10 years to develop. Suggest 2 reasons why it is predicted that a Coronavirus vaccine can be developed in a shorter time frame? (2 marks)
Bio 3/4
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whys

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Re: Answer a biology question!
« Reply #19 on: July 30, 2020, 06:09:59 pm »
+4
//
b) Good answer, however it might be necessary to say that Taq polymerase catalyses the joining of complementary DNA nucleotides to the DNA segment.
c) Slight correction. RNA polymerase transcribes the 3 structural genes in the lac operon, not DNA polymerase. This is so the proteins (enzymes used to break down lactose) can be made, first by creating the mRNA strand complementary to that segment of DNA, which requires RNA polymerase.

SmartWorker

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Re: Answer a biology question!
« Reply #20 on: July 30, 2020, 06:18:23 pm »
+2
b) Good answer, however it might be necessary to say that Taq polymerase catalyses the joining of complementary DNA nucleotides to the DNA segment.
c) Slight correction. RNA polymerase transcribes the 3 structural genes in the lac operon, not DNA polymerase. This is so the proteins (enzymes used to break down lactose) can be made, first by creating the mRNA strand complementary to that segment of DNA, which requires RNA polymerase.

Yep, thanks whys :) Confused DNA with RNA, I hope I don't make the same mistake again haha.
Bio 3/4
KLD (2021)

"Everyone you meet is fighting a battle you know nothing about. Be kind. Always." ― Brad Meltzer