VCE Biology Question Thread

[thushan]

There - may - be some matches, because there could be another fragment of the suspect's DNA that was cut, that happens to have an identical length to the fragment of DNA from crime scene.

[vox nihili]

Yep with this one, all I am asking is whether or not the use a specific gene loci for all the suspects?

For example, if they use restriction enzymes that cut a specific recognition site on the DNA of the suspects, what if they cut different fragments on the suspect's DNA as compared to the crime scene DNA fragment? Wouldn't that result in no matches?

No, but they use specific restriction enzymes. DNA from different people cut with the same restriction enzyme should and will show different fragmentation patterns. The chances of two samples having the same fragmentation pattern are infinitesimally small.

[cosine]

No, but they use specific restriction enzymes. DNA from different people cut with the same restriction enzyme should and will show different fragmentation patterns. The chances of two samples having the same fragmentation pattern are infinitesimally small.

Yeh but my main concern is that say they got a sample of blood from the crime scene, right? And that sample has DNA in it obviously. So what happens now with the restriction enzyme, does the enzyme target the whole DNA genome of the cell/s obtained or do the investigators obtain one specific segment of DNA/chromosome and use that to use a restriction enzyme to cut out the fragments, and obtain the same specific segment of DNA/chromosome from the suspects and use the same enzyme to cut out the fragments and which ever produces the same sizes/length is the suspect?

I get that they use specific restriction enzymes that will cause the same size fragments of DNA in the real suspect, but where in the blood sample does the restriction enzyme cut the DNA?

[thushan]

The whole genome, I think?

[vox nihili]

Yeh but my main concern is that say they got a sample of blood from the crime scene, right? And that sample has DNA in it obviously. So what happens now with the restriction enzyme, does the enzyme target the whole DNA genome of the cell/s obtained or do the investigators obtain one specific segment of DNA/chromosome and use that to use a restriction enzyme to cut out the fragments, and obtain the same specific segment of DNA/chromosome from the suspects and use the same enzyme to cut out the fragments and which ever produces the same sizes/length is the suspect?

I get that they use specific restriction enzymes that will cause the same size fragments of DNA in the real suspect, but where in the blood sample does the restriction enzyme cut the DNA?

In theory, you can do either.

In practice, they don't ever use this technique. PCR is much quicker, can be used with smaller samples etc...

[tashhhaaa]

Some don't actually lyse the cells. Generally though lysis is a strategy that viruses use to get out of the cell. They need to be able to get around. Also, there are so many cells available for the viruses that they can afford to push the host cell machinery so hard that it kills them.

cheers!

[grindr]

Question regarding neurotransmitter movement in synapse,
The answer is B, why isn't it C, active transport?

[cosine]

Question regarding neurotransmitter movement in synapse,
The answer is B, why isn't it C, active transport?

Stupid question because endocytosis is a form of active transport. SO technically both are correct but endocytosis is more correct because that implies active transport, plus the bulk transport (not one single neurotransmitter is engulfed, but rather many at a time) inside the cell.

[Biology24123]

Stupid question because endocytosis is a form of active transport. SO technically both are correct but endocytosis is more correct because that implies active transport, plus the bulk transport (not one single neurotransmitter is engulfed, but rather many at a time) inside the cell.

But B is more correct

[cosine]

Few questions:

1. Do polygenic inheritance involve recessive and dominant alleles, or is it mainly codominance?

2. For the attached question, can you explain it to me?

[cosine]

- Also for the attached, It is obviously between genetic drift and gene flow. I know that gene flow is the change of allele frequencies in a population's gene pool due to migration, and can involve the addition of alleles (immigration) or removal of alleles (emmigration), where as genetic drift is the change of allele frequencies of a population due to chance events.
So because the island is no longer connected to the mainland, migration is not possible for the frogs, or at least unlikely. So over time, the allele that has disappeared may have been a result of genetic drift, possibly the bottleneck effect??
 
- For the second question, please don't tell me the answer but just guide me, because I still don't understand HOW mtDNA relates to the Out of Africa Theory, can someone help me understand this?

[Sine]

Few questions:

1. Do polygenic inheritance involve recessive and dominant alleles, or is it mainly codominance?

2. For the attached question, can you explain it to me?

1. Co-dominance is where 2 alleles are simultaneously expressed to their fullest extent in the phenotype. Polygene inheritance is more of a cumulative impact not really dominant vs recessive as it's not like only a single allele impacting the phenotype this is for stuff like height or skin pigmentation.
2.1/4 x 3/4 = 3/16, just multiplying probabilities not sure about this one.

- Also for the attached, It is obviously between genetic drift and gene flow. I know that gene flow is the change of allele frequencies in a population's gene pool due to migration, and can involve the addition of alleles (immigration) or removal of alleles (emmigration), where as genetic drift is the change of allele frequencies of a population due to chance events.
So because the island is no longer connected to the mainland, migration is not possible for the frogs, or at least unlikely. So over time, the allele that has disappeared may have been a result of genetic drift, possibly the bottleneck effect??
 
- For the second question, please don't tell me the answer but just guide me, because I still don't understand HOW mtDNA relates to the Out of Africa Theory, can someone help me understand this?

1. I would say genetic drift as in the isolated population allele frequencies would be different and due to the smaller population genetic drift has a greater impact and thereby a greater chance of losing alleles. Additionally A. We can't really associate mutation with loss of alleles more with gain of alleles. B. non-random mating could be it but there is nothing say that it is. D. Isolated population-No gene flow, gene flow would be more favourable of gains of alleles than loss.

Think back to the theory of Out-of Africa vs Multi regional theory and the properties of mtDNA(does not recombine, inherited maternally, high mutation rate)

Spoiler

2. It's A, kinda what we learn when we learn both hypothesis' however I will explain it. So the out-of Africa theory suggests that homo sapiens left Africa thrice but only the African population was able to survive, thus they were existent for a longer time thus more time for mutations to occur, then homo sapiens left Africa to all around the world.

Haha Thanks Biology24123

[Biology24123]

- Also for the attached, It is obviously between genetic drift and gene flow. I know that gene flow is the change of allele frequencies in a population's gene pool due to migration, and can involve the addition of alleles (immigration) or removal of alleles (emmigration), where as genetic drift is the change of allele frequencies of a population due to chance events.
So because the island is no longer connected to the mainland, migration is not possible for the frogs, or at least unlikely. So over time, the allele that has disappeared may have been a result of genetic drift, possibly the bottleneck effect??
 
- For the second question, please don't tell me the answer but just guide me, because I still don't understand HOW mtDNA relates to the Out of Africa Theory, can someone help me understand this?

Haha, he said not to say the answer

[BakedDwarf]

Few questions:

2. For the attached question, can you explain it to me?

Let:
A = normal allele
a = albino allele

Pr = Pr(aa) x Pr(Aa ∪ AA)
    = 1/4 x 3/4
    = 3/16 (what sine said)

- For the second question, please don't tell me the answer but just guide me, because I still don't understand HOW mtDNA relates to the Out of Africa Theory, can someone help me understand this?

EDIT: I don't know how to put the spoiler tag, but i think i answered the question.

As we know the non-coding regions of mtDNA mutate at a fast rate, a population that has been separated for a long time tends to accumulate mutations in their mtDNA. Hence, the more mutations a population has accumulated over time, the longer its evolutionary origin.

African populations have the most variation in their mtDNA than any other human population, indicating a long evolutionary history. This reinforces the 'Out-of-Africa' hypothesis that states that homo sapiens evolved in Africa and then migrated to all other parts of the world

[cosine]

EDIT: I don't know how to put the spoiler tag, but i think i answered the question.

As we know the non-coding regions of mtDNA mutate at a fast rate, a population that has been separated for a long time tends to accumulate mutations in their mtDNA. Hence, the more mutations a population has accumulated over time, the longer its evolutionary origin.

African populations have the most variation in their mtDNA than any other human population, indicating a long evolutionary history. This reinforces the 'Out-of-Africa' hypothesis that states that homo sapiens evolved in Africa and then migrated to all other parts of the world

I don't get it. African populations have the most variations in their mtDNA sure, but why does that suggest the out of africa theory? So you are saying that because african populations have the most variation/mutations that have accumulated in their mtDNA, they have existed for a longer time because as time proceeds, mtDNA mutates at a known rate? I get this part, but could you relate this fact with the other populations in the world? What, do other populations in the world, say Australia, have less mutations accumulated in their mtDNA suggesting they have been around for a less amount of time? But did not we all diverge from Homo Sapiens in Africa? So wouldn't this mean we all initially had the same mtDNA? Not sure...