VCE Biology Question Thread

[cosine]

For the attached;

1. It says that snakes and legless lizards evolved separately from ancestors. Does this not mean divergent evolution? Like they both shared a common ancestor, and because they were subject to different environments or what ever, they evolved separately, which is the definition of speciation? Why is B incorrect?

2. In a group of organisms, individuals genetically identical at a particular single gene locus show a variety of phenotypes for the trait. Cannot this be polygenic inheritance? It all adds up to me because if one particular gene locus is identical, and yet they show variation for the same phenotype, then another gene locus must be governing this trait as well, right? I understand how environmental conditions could also be correct, but I would like if someone could explain to me if my reasoning for B is incorrect/correct?

3. During Meiosis, crossing over and recombination occur between homologous chromosomes. Describe the outcome of recombination.

"Recombination occurs when homologous chromosomes cross over during Meiosis and interchange alleles. The outcome of recombination is an increase in genetic variation in the offspring of the parents."

Would that have gotten the two marks?
When do you know to write two points of information?
Can you write the points in dot points, so not in a paragraph?
What is the difference between recombination and crossing over?

4. A particular specific of crop was genetically engineered to contain this gene. Such plants are referred to as GM (Genetically Modified). Explain why a farmer might choose to grow a crop that was genetically engineered to be resistant to insects, rather than spray the crop with insecticide?

I said because the growing GM crops, the future generations of the crop will also be able to be resistant to the insecticide, and so the farmer has less worries about his crops.

My query is, Can GM plants replicate their plasmids and pass it down to offspring? I know bacteria can, but can also plant cells do this? Because the following question is an experiment about the pollen of the GM plants fertilising the non-GM plants.

5. The differences between mitochondrial DNA recorded are the results of Base substitutions. There are 77 nucleotide differences between Human 1 and Chimpanzee 1. Explain why 77 nucleotide differences is a minimum number of base substitutions.

I said that some bases may have been mutated but the same nucleotide was added in both the chimpanzee and human DNA, so it would not be observed as a difference.

Is this correct? Answer just says that mutations are reversible. Can someone explain what is meant by this?

[sushibun]

By the way I just looked at the study design and I have some questions.
1) What do they mean by the the role of ATP and ADP in energy transformations?

2) What are the the main inputs and outputs of the light dependent and light independent stages?

3) Where are B cells or T cells when they recognise an antigen? Are they in the lymphnodes, blood, interstitial fluid? Anywhere?

4)  What is the role of the lymphatic system in the innate and adaptive immune response?
The lymphocytes in lymphnodes act as filters or nets for pathogens in the lymph fluid? The thymus is where the T cells mature. Does the spleen do anything?

5) Do we need to know the difference between and attenuated and inactivated vaccine? And do we need to remember examples/process of how vaccines/antibody serums are made?

6) Can someone give me a run down of what phylogeny is?

7) What are some shared characteristics of hominoids? Is it their use of tools, being very social?

I'm sorry if this is very long, I just didn't want to post many times. Thanks in advance if you do answer some of my questions!

[sushibun]

So B technically is correct?

And for the first question, I may have not been clear in what my question was. The primary structure of haemoglobin is given, and the mRNA codons will be exactly that of the amino acid sequence codons. However, the mRNA codons would not necessarily reflect the exact nucleotide sequence of the DNA molecule because the introns would have been removed. You see how question 14 is asking about the DNA molecule, do we have to assume that the DNA molecule transcripted the mRNA molecule with no introns? Because what might be the 12th nucleotide in the DNA molecule may be something else in the mRNA codon sequence, because the introns would have been removed?

Yeah B is technically correct.
Since its VCAA I guess you would have to assume that the DNA sequence only had exons unless stated otherwise

[cosine]

By the way I just looked at the study design and I have some questions.
1) What do they mean by the the role of ATP and ADP in energy transformations?
ATP provides the energy when the further phosphate breaks off, whereas ADP captures the energy when an inorganic phosphate binds to the two phosphates producing ATP

2) What are the the main inputs and outputs of the light dependent and light independent stages?
Light dependent:
Inputs: Water, Sun light, ADP + Pi and NADP+
Outputs: Oxygen, ATP and NADPH

Light Independent:
Inputs: ATP, NADPH, Carbon Dioxide
Outputs: Glucose, NADP+, ADP + Pi and Water

3) Where are B cells or T cells when they recognise an antigen? Are they in the lymphnodes, blood, interstitial fluid? Anywhere?
Helper T cells are free-floating in the interstitial fluids and recognise the APCs.
Naive B cells are found in the lymph nodes
Memory B cells are found in the lymph nodes and spleen
Plasma B cells (not too sure someone correct me) are found in the blood as they produce antibodies
Cytotoxic T cells are also free-floating as they need to encounter virally infected cells

4)  What is the role of the lymphatic system in the innate and adaptive immune response?
The lymphocytes in lymphnodes act as filters or nets for pathogens in the lymph fluid? The thymus is where the T cells mature. Does the spleen do anything?

The lymphatic system is responsible for the specific third line of defence. It is the collection of organs/tissues that produce and store the lymphocytes of the immune system. Yes, the lymphocytes in the lymph nodes act as filters or nets for pathogens, and the thymus is there T cells mature. The spleen usually stores Lymphocytes as well (particularly memory cells) and also destroys old/faulty blood cells.

5) Do we need to know the difference between and attenuated and inactivated vaccine? And do we need to remember examples/process of how vaccines/antibody serums are made?
I don't think so - just know what a vaccine does and it's significance.

6) Can someone give me a run down of what phylogeny is?
Phylogeny is the the features that organisms show because of the relatedness to recent common ancestors. Because these species share this recent common ancestor, they both have the same underlying characteristics/features/phylogeny because they evolved from the same ancestor which possessed this feature.

7) What are some shared characteristics of hominoids? Is it their use of tools, being very social?


I'm sorry if this is very long, I just didn't want to post many times. Thanks in advance if you do answer some of my questions!

[Sine]

Since X and Y chromosomes are not homologous chromosomes, is it still called non-disjunction if they fail to separate during either anaphase.

[Bruzzix]

Since X and Y chromosomes are not homologous chromosomes, is it still called non-disjunction if they fail to separate during either anaphase.

This question actually came up in my class once and my teacher said he didn't know and that it's way out of the study design so don't even worry about it. It would be interesting to know the answer though.

[sunshine98]

Since X and Y chromosomes are not homologous chromosomes, is it still called non-disjunction if they fail to separate during either anaphase.

According to VCAA U4 2007 question 1c yep  its still called non disjunction of chromosomes (the question had it occurring at anaphase 1) 

[Bruzzix]

According to VCAA U4 2007 question 1c yep  its still called non disjunction of chromosomes (the question had it occurring at anaphase 1)

Champion

[warya]

Guys what even is non-dysjunction 

[katiesaliba]

Guys what even is non-dysjunction 

When chromosomes fail to separate in anaphase I or II of meiosis.

[Bruzzix]

For the attached;

1. It says that snakes and legless lizards evolved separately from ancestors. Does this not mean divergent evolution? Like they both shared a common ancestor, and because they were subject to different environments or what ever, they evolved separately, which is the definition of speciation? Why is B incorrect?
A. analogy
The key words here are seperately and ancestors. This question I think is more to test your reading skills than actual knowledge which is annoying. Those words imply that the two organisms have different lineages otherwise it would say they evolved from an ancestor or a common ancestor.

2. In a group of organisms, individuals genetically identical at a particular single gene locus show a variety of phenotypes for the trait. Cannot this be polygenic inheritance? It all adds up to me because if one particular gene locus is identical, and yet they show variation for the same phenotype, then another gene locus must be governing this trait as well, right? I understand how environmental conditions could also be correct, but I would like if someone could explain to me if my reasoning for B is incorrect/correct?
If all the organisms are genetically identical at that gene locus then that means they will all have the same alleles and they're all going to express the exact same trait that that gene codes for.. Unless environmental influences change that (epigenetics is one example). It is true that there could be other gene loci that cause phenotypic variation, but we're talking about just one trait which is only coded for by one gene locus. Therefore the answer cannot be polygenic inheritance
3. During Meiosis, crossing over and recombination occur between homologous chromosomes. Describe the outcome of recombination.

"Recombination occurs when homologous chromosomes cross over during Meiosis and interchange alleles. The outcome of recombination is an increase in genetic variation in the offspring of the parents."

Would that have gotten the two marks?
I think it depends on the question and what the examiner was looking for in the answer. If they wanted you describe the process of recombination and what effects it has on the offspring you would get full marks.
When do you know to write two points of information?
Usually two dot points of information are required for two mark questions
Can you write the points in dot points, so not in a paragraph?
Yes, definitely. Whatever helps you to set out your answer as clearly as possible.
What is the difference between recombination and crossing over?
I think they are the same thing? Not too sure.

4. A particular specific of crop was genetically engineered to contain this gene. Such plants are referred to as GM (Genetically Modified). Explain why a farmer might choose to grow a crop that was genetically engineered to be resistant to insects, rather than spray the crop with insecticide?

I said because the growing GM crops, the future generations of the crop will also be able to be resistant to the insecticide, and so the farmer has less worries about his crops.

My query is, Can GM plants replicate their plasmids and pass it down to offspring? I know bacteria can, but can also plant cells do this? Because the following question is an experiment about the pollen of the GM plants fertilising the non-GM plants.

OK there are some problems here. GM plants DO NOT have plasmids!   We insert the gene of interest into a plasmid then mix the modified bacteria with plant cells such as cut up pieces of leaf or stem. Some plant cells uptake the plasmid and the desired gene(s) are inserted into one of the plants chromosomes. We don't need to worry about what happens to the plasmid thereafter but it definitely doesn't have an effect on the plant on its own. The plants now have a permanently modified genome so the offspring will inherit the modified chromosome.
Also I think better answers to the question include: saves money, saves time, removes risk of consumer being harmed form insecticide residue, reduces potential environmental damage from crop/agricultural runoff.

5. The differences between mitochondrial DNA recorded are the results of Base substitutions. There are 77 nucleotide differences between Human 1 and Chimpanzee 1. Explain why 77 nucleotide differences is a minimum number of base substitutions.

I said that some bases may have been mutated but the same nucleotide was added in both the chimpanzee and human DNA, so it would not be observed as a difference.
I think you understand the general idea but it could be put into better words. You could perhaps say something along the lines of 'a base substitution occurred in the mtDNA and some time later that same base underwent another substitution mutation so that it was replaced by the base that was initially there. That's essentially what it means by reversible mutations although I don't like that phrasing.'
Is this correct? Answer just says that mutations are reversible. Can someone explain what is meant by this?

[cosine]

Here comes my post-exam influx:

Question 13:

 Isnt apoptosis only initiated from signals exterior to the cell? If not, then can someone give an example of an interior signal, is it as simple as the DNA is altered so it signals death?

Second part to it is, why would perfectly healthy cells be programmed to die? Answer is D

Question 17:

Where does it say/ how do we know that the lactase is a selective advantage? I said D is the answer can someone explain why D is incorrect?

Question 18:

How do primers anneal? Doesn't the DNA primase (RNA Polymerase) synthesise the primers onto the DNA template strands?

Question: When you write the phenotypic ratio, if you are dealing with males and females, is the normal female a different phenotype as the normal male, right?

Question: What is a polygenic inheritance?
"A trait that is inherited in more than one gene locus"
Is this correct?

[BakedDwarf]

So i just did the 2013 VCAA exam, and i've got questions about whether or not I would get marks for my responses. I realise this is very long, and any help is greatly appreciated (really)

Question 1. c. ii

Name the two inputs of the light-independent stage and describe their role. (2 marks)

My answer:
- NADPH: Donates its hydrogen ion to a three-carbon compound to reduce it
- ATP: Provides the energy for the light independent stage

VCAA answer:
- NADPH: Carries hydrogen ions
- ATP: Provides energy to form glucose

Question 3. c. ii

Suggest how a hormone can produce different responses in smooth muscle cells and liver cells. (1 mark)

My answer:
When the hormone binds to its specific receptor, different signal transduction pathways occur in different cells, resulting in different cellular responses

VCAA answer:
There may be different receptors or different secondary molecules

Question 4. c.

Explain how regular booster injections work and why they are necessary (2 marks)

My answer:
The booster injection injects an attenuated form of the antigen into the individual again. This is necessary because the individual mounts another specific immune response against this antigen, which increases the amount of antibodies and memory cells specific to it.

VCAA answer:
Booster injections are used to produce more memory B cells because memory cells are short lived

Question 5. b.

5. b. A teenager with a family history of an autoimmune disease underwent a genetic screen for the disease. After receiving a positive result for the genetic screen, she had an additional autoantibody test. The result of this autoantibody test was negative. Explain why the autoantibody test could be negative even though the genetic screen was positive. (2 marks)

My answer: The teenager has inherited the gene/s for the autoimmune disease and so the genetic screen was positive for the disease. However, the gene/s have not been yet expressed by the teenager and so she does not have the autoantibodies, resulting in a negative for the test.

VCAA answer:
The genetic screen indicates the potential to develop the disease and the absence of autoantibodies indicates that the
disease has not yet been switched on.

Question 8. b.

8. b. Briefly explain the biological significance of the process of meiosis (2 marks)

My answer:
Meiosis is a type of cell division that produces haploid cells. This allows fertilisation to successfully occur between two individuals to produce a diploid offspring and so to pass down their genes.

VCAA answer:
Two of:
- meiosis provides variation in offspring due to (one of): independent assortment or crossing over and recombination
- fertilisation results in increased variation through joining of gametes
- meiosis ensures gametes are haploid
- increases the chance of a species surviving if there are different selection pressures.

Question 9. b. ii.

9. b. ii. Why is it an advantage to have a diverse gene pool among a population (2 marks)

My answer:
Not all of the organisms would respond to the change in environment or selection pressures in the same way. Hence, they won't be greatly exposed to extinction if the environmental/selection pressure change negatively affects some of them.

VCAA answer:
Diversity produces a variety of phenotypes and there is an increased chance of survival of the population if the environment changes

Question 9. c.

9. c. Explain the meaning of the bottleneck effect with reference to allele frequencies  (1 mark)

My answer:
The population is reduced in size that even it is grows, its genetic diversity and range of allele frequencies does not

VCAA answer:
A severe reduction in genetic diversity due to a catastrophe that may change allele frequency

Question 11. a.

11. a. Explain the significance of difference of:                                                           (2 marks)
          - a wider pelvic structure in A. africanus than H. neanderthalensis
          - a greater arm to leg length ratio in A. africanus than H. neanderthalensis

My answer:
- A less wider pelvic structure in H. neanderthalensis allowed for greater balance whilst bipedal
- A decrease in arm to leg ratio in H. neanderthalensis increased the eye level above the ground, allowing the identification of preys/predators for a greater distance

VCAA answer:
- Wider pelvis: harder to walk upright as tips centre of gravity in A. africanus
- Greater arm to leg ratio: knuckle walking in A. africanus

[Bruzzix]

Here comes my post-exam influx:

Question 13:

 Isnt apoptosis only initiated from signals exterior to the cell? If not, then can someone give an example of an interior signal, is it as simple as the DNA is altered so it signals death?

Second part to it is, why would perfectly healthy cells be programmed to die? Answer is D
There are quite a few reasons. One that I can think of from the top of my head is during development in the womb, the fetus has apoptosis occur in certain parts of the body to form structure. For example apoptosis occurs in columns at the end of the feet to form toes.
Question 17:

Where does it say/ how do we know that the lactase is a selective advantage? I said D is the answer can someone explain why D is incorrect?
The question stem states that milk is "a safe and nutritious food which is readily available year-round". Thus it would be advantageous to have an easily accessible source of nutrition to promote growth an provide energy for daily activities etc. Only people with the lactase enzyme though can digest milk properly so they get the advantage whereas those without lactase don't get that same advantage. Option D isn't necessarily incorrect, it's just that that conclusion can't be made from the given information.
Question 18:

How do primers anneal? Doesn't the DNA primase (RNA Polymerase) synthesise the primers onto the DNA template strands?
Our DNA is cooled to 50-55°C which is the optimal temperature for the primers to anneal. We usually artificially create primers in the lab with the specific sequence that we want and use those.
Question: When you write the phenotypic ratio, if you are dealing with males and females, is the normal female a different phenotype as the normal male, right?
That's correct
Question: What is a polygenic inheritance?
"A trait that is inherited in more than one gene locus"
Is this correct?
Essentially, but you could go into further detail.

[vox nihili]

Here comes my post-exam influx:

Question 13:

 Isnt apoptosis only initiated from signals exterior to the cell? If not, then can someone give an example of an interior signal, is it as simple as the DNA is altered so it signals death?

Second part to it is, why would perfectly healthy cells be programmed to die? Answer is D

Question 17:

Where does it say/ how do we know that the lactase is a selective advantage? I said D is the answer can someone explain why D is incorrect?

Question 18:

How do primers anneal? Doesn't the DNA primase (RNA Polymerase) synthesise the primers onto the DNA template strands?

Question: When you write the phenotypic ratio, if you are dealing with males and females, is the normal female a different phenotype as the normal male, right?

Question: What is a polygenic inheritance?
"A trait that is inherited in more than one gene locus"
Is this correct?

13. Definitely not. Apoptosis can be initiated by signals both internally and externally. DNA damage is an example of such an event that would induce apoptosis, but there are many.

17. Commonsense dictates that having the capacity to produce lactase is an evolutionary advantage. They spell it out pretty clearly: it's a food source, available year round etc etc. D is an unreasonable conclusion. The mutation that gave rise to lactase just occurred later on in the European ancestry. Doesn't mean that the antecedents to those in whom the mutation arose are then excluded from the family tree.

18. In DNA replication, yes. This is PCR. In PCR they're just there. Primers anneal passively.

Polygenic traits are those that are under the control of more than one gene locus.

If you're working with sex-linked traits, separate males and females. Otherwise don't bother as it makes no difference

So i just did the 2013 VCAA exam, and i've got questions about whether or not I would get marks for my responses. I realise this is very long, and any help is greatly appreciated (really)

Question 1. c. ii

Name the two inputs of the light-independent stage and describe their role. (2 marks)

My answer:
- NADPH: Donates its hydrogen ion to a three-carbon compound to reduce it
- ATP: Provides the energy for the light independent stage

VCAA answer:
- NADPH: Carries hydrogen ions
- ATP: Provides energy to form glucose

Question 3. c. ii

Suggest how a hormone can produce different responses in smooth muscle cells and liver cells. (1 mark)

My answer:
When the hormone binds to its specific receptor, different signal transduction pathways occur in different cells, resulting in different cellular responses

VCAA answer:
There may be different receptors or different secondary molecules

Question 4. c.

Explain how regular booster injections work and why they are necessary (2 marks)

My answer:
The booster injection injects an attenuated form of the antigen into the individual again. This is necessary because the individual mounts another specific immune response against this antigen, which increases the amount of antibodies and memory cells specific to it.

VCAA answer:
Booster injections are used to produce more memory B cells because memory cells are short lived

Question 5. b.

5. b. A teenager with a family history of an autoimmune disease underwent a genetic screen for the disease. After receiving a positive result for the genetic screen, she had an additional autoantibody test. The result of this autoantibody test was negative. Explain why the autoantibody test could be negative even though the genetic screen was positive. (2 marks)

My answer: The teenager has inherited the gene/s for the autoimmune disease and so the genetic screen was positive for the disease. However, the gene/s have not been yet expressed by the teenager and so she does not have the autoantibodies, resulting in a negative for the test.

VCAA answer:
The genetic screen indicates the potential to develop the disease and the absence of autoantibodies indicates that the
disease has not yet been switched on.

Question 8. b.

8. b. Briefly explain the biological significance of the process of meiosis (2 marks)

My answer:
Meiosis is a type of cell division that produces haploid cells. This allows fertilisation to successfully occur between two individuals to produce a diploid offspring and so to pass down their genes.

VCAA answer:
Two of:
- meiosis provides variation in offspring due to (one of): independent assortment or crossing over and recombination
- fertilisation results in increased variation through joining of gametes
- meiosis ensures gametes are haploid
- increases the chance of a species surviving if there are different selection pressures.

Question 9. b. ii.

9. b. ii. Why is it an advantage to have a diverse gene pool among a population (2 marks)

My answer:
Not all of the organisms would respond to the change in environment or selection pressures in the same way. Hence, they won't be greatly exposed to extinction if the environmental/selection pressure change negatively affects some of them.

VCAA answer:
Diversity produces a variety of phenotypes and there is an increased chance of survival of the population if the environment changes

Question 9. c.

9. c. Explain the meaning of the bottleneck effect with reference to allele frequencies  (1 mark)

My answer:
The population is reduced in size that even it is grows, its genetic diversity and range of allele frequencies does not

VCAA answer:
A severe reduction in genetic diversity due to a catastrophe that may change allele frequency

Question 11. a.

11. a. Explain the significance of difference of:                                                           (2 marks)
          - a wider pelvic structure in A. africanus than H. neanderthalensis
          - a greater arm to leg length ratio in A. africanus than H. neanderthalensis

My answer:
- A less wider pelvic structure in H. neanderthalensis allowed for greater balance whilst bipedal
- A decrease in arm to leg ratio in H. neanderthalensis increased the eye level above the ground, allowing the identification of preys/predators for a greater distance

VCAA answer:
- Wider pelvis: harder to walk upright as tips centre of gravity in A. africanus
- Greater arm to leg ratio: knuckle walking in A. africanus

1cii: yep, that's fine. Hydrogen carrier is better but I suspect you'd get marks for both.

3cii. yep, that's fine. Different signal transduction pathways implies different secondary messengers.

4c. be careful about adding extra information. You weren't asked to define a booster and your definition is actually not correct. Everything else you say is right, but poorly worded, though I suspect you could lose marks for having incorrectly defined a booster. They're not always just attenuated viruses/cells. Vaccines can come in a number of forms. With that said, it's hard to tell sometimes, you may pull marks for that one. If I were marking it, I'd probably give the marks.

5b. No, your answer is wrong. It has nothing to do with gene expression I'm afraid. Cruel question though.

8b. You'd get one mark. You really should have acknowledged that meiosis exists to create variation. Sadly, meiosis is often really poorly taught. Its significance comes from the fact that it generates an enormous amount of variation.

9bii. 1 mark for saying there's a greater chance of extinction, but you've not expressed your well here. Look at the VCAA answer for a guide.

9c. No marks for this one. Have a look over bottlenecks again, this isn't right. A bottleneck reduces the genetic variation of a population; however, it does not stop the population from becoming more varied thereafter.

11a. No marks. You didn't answer the question. They asked for why a greater pelvic width was significant and you explained why a smaller pelvic width was. Likewise, you explained a decrease in arm to leg ratio when they asked about a greater arm to leg ratio. Read the question carefully.