VCE Biology Question Thread

[AhNeon]

When youre adding a gene to a plasmid, does any section of the plasmid get cut out?
Is there any difference that we need to know between protein channels for facilitated diffusion and those for active transport?

[The Usual Student]

When youre adding a gene to a plasmid, does any section of the plasmid get cut out?
Is there any difference that we need to know between protein channels for facilitated diffusion and those for active transport?

YEP! A portion of the plasmids DNA will be cut out and from there some of it will bind back to plasmids again and some of it wont.
And i don't think so to your second question. I haven't seen a distinction being made in any exam papers.

[vox nihili]

My teacher was telling us about reverse transcription involving reverse transcriptase making a DNA complementary copy of the mature mRNA. DNA polymerase then makes a complementary strand of DNA (cDNA) to the existing DNA strand. Specific restriction enzymes then cut the double stranded DNA at specific sites. The same restriction enzymes cut out a section of a plasmid and the gene is inserted into the plasmid. DNA ligase then sticks it all together. The gene is inserted into a plasmid and the plasmid is inserted into a bacteria. If the gene from the plasmid is expressed in the single circular chromosome in the bacteria, this reverse transcription is considered successful.

I was wondering what this process is used for? If the bacteria is then inserted into an organism, is it then considered a genetically modified organism, or a transgenic organism?

Nothing at all relevant to VCE. You don't need to know about reverse transcriptase.






Explanation not relevant to VCE

This is actually how you get bacteria to express a gene. As I'm sure you know, bacteria are used to make insulin for diabetics, growth hormone and so on.
Bacteria can't remove introns from genes. So when you put a gene into a bacterium that you want to be expressed, you need to take the introns out. THe way you do this is to capture the mature mRNA for that particular gene, then use reverse transcriptase to get the DNA sequence for that gene—introns removed—so that you can chuck that into a plasmid

When youre adding a gene to a plasmid, does any section of the plasmid get cut out?
Is there any difference that we need to know between protein channels for facilitated diffusion and those for active transport?

1. Nope, not unless you're trying to
2. Not really. But remember, it's carriers and not channels involved in active transport.

[The Usual Student]

Nothing at all relevant to VCE. You don't need to know about reverse transcriptase.






Explanation not relevant to VCE

This is actually how you get bacteria to express a gene. As I'm sure you know, bacteria are used to make insulin for diabetics, growth hormone and so on.
Bacteria can't remove introns from genes. So when you put a gene into a bacterium that you want to be expressed, you need to take the introns out. THe way you do this is to capture the mature mRNA for that particular gene, then use reverse transcriptase to get the DNA sequence for that gene—introns removed—so that you can chuck that into a plasmid

1. Nope, not unless you're trying to
2. Not really. But remember, it's carriers and not channels involved in active transport.

Doesn't it? then how do they make room for the new DNA to be inserted in? I learnt in class u use restriction enzymes on the plasmid to cut out a space for the new DNA?

[vox nihili]

Doesn't it? then how do they make room for the new DNA to be inserted in? I learnt in class u use restriction enzymes on the plasmid to cut out a space for the new DNA?

It depends on how you do it, you're right I should clarify that.

If you cut with a single enzyme, then it won't be any problem and you won't lose any of the original plasmid. If you cut with two, obviously the intervening region between the cut bits will of course be lost.

You tend to set things up though so that you only have to cut with one restriction enzyme, but that's waaaaay beyond the VCE course and amounts to sorcery, frankly :p

[AhNeon]

Do bacteria produce pre-mRNA, like do they still go through the whole methyl cap and poly-A tail process (obviously no splicing to remove introns but yh)
Also, do transcripition factors have the ability to repress and initiate transcription of a gene?

[usernameincorrect]

Can anyone help me out with part ei and eii? I've read the examiners report and don't understand it 
Thanks in advance!

[The Usual Student]

Can anyone help me out with part ei and eii? I've read the examiners report and don't understand it 
Thanks in advance!

You have two chromosomes we are dealing (1 and 2)  with: BOTH REPLICATE so visually it looks like
                                                                                    XX ( chromosome 1) and XX ( chromosome 2)
Now the two sister chromatids will cross over which results in recombinant DNA!
So for chromosome 1: The chromatids have a different combination of alleles now!
2 are normal whilst 2 are recombined
Now the same thing happens with chromosome 2
2 are normal whilst 2 are recombined
So we want the chance a sperm cell has both a normal 2 and a normal 1 chromosome
There is 0.5 chance of getting a normal 1 chromosome and 0.5 chance of getting a normla 2 chromosome
HENCE 0.5 X 0.5 = 0.25
AKA 1/4

idk if that is correct but that is how i would figure it out

[vox nihili]

Do bacteria produce pre-mRNA, like do they still go through the whole methyl cap and poly-A tail process (obviously no splicing to remove introns but yh)
Also, do transcripition factors have the ability to repress and initiate transcription of a gene?

Pretty sure they can do polyA and methyl-cap, but they have other mechanisms of achieving the same too. The processes would be different, because the requirements in bacterial cells are different. Hopelessly vague answer, but mainly because it doesn't matter

And yes, transcription factors are an absolute requirement of gene transcription in eukaryotes.

[homosapien]

Do glycolipids and glycoproteins both aid in cell recognition or is it just glycolipids that do that?
If not, what do glycoproteins actually do?

[The Usual Student]

Pretty sure they can do polyA and methyl-cap, but they have other mechanisms of achieving the same too. The processes would be different, because the requirements in bacterial cells are different. Hopelessly vague answer, but mainly because it doesn't matter

And yes, transcription factors are an absolute requirement of gene transcription in eukaryotes.

can someone fill me in on " transcription factors?"
Just what they do, I probably know the concept just not the name :/

And to the question above
They are both involved in it at a VCE point of view

[vox nihili]

can someone fill me in on " transcription factors?"
Just what they do, I probably know the concept just not the name :/

And to the question above
They are both involved in it at a VCE point of view

They're just extra proteins that help RNA polymerase know where to latch on and transcribe.

[sweetcheeks]

Is it pyruvate or Acetyl CoA that enters the mitochondria/krebs cycle?

[The Usual Student]

They're just extra proteins that help RNA polymerase know where to latch on and transcribe.

is that interchangeable with the RNA primer?

[usernameincorrect]

You have two chromosomes we are dealing (1 and 2)  with: BOTH REPLICATE so visually it looks like
                                                                                    XX ( chromosome 1) and XX ( chromosome 2)
Now the two sister chromatids will cross over which results in recombinant DNA!
So for chromosome 1: The chromatids have a different combination of alleles now!
2 are normal whilst 2 are recombined
Now the same thing happens with chromosome 2
2 are normal whilst 2 are recombined
So we want the chance a sperm cell has both a normal 2 and a normal 1 chromosome
There is 0.5 chance of getting a normal 1 chromosome and 0.5 chance of getting a normla 2 chromosome
HENCE 0.5 X 0.5 = 0.25
AKA 1/4

idk if that is correct but that is how i would figure it out

If that happens, the way I'm looking at it, there will be four gamates, 2 will have the recombinant chromosome 1 and 2, and two gamates will have the normal 1 and 2. I must be misunderstanding something here