VCE Biology Question Thread

[EllingtonFeint]

Could somebody please just give me a very simple one sentence description/purpose of each of the following parts of an antibody please... I’ve just been researching it and I don’t think I’m really grasping any info
-Light chain
-Heavy chain
-Heavy chain bridges
-Phagocyte attracting region
-constant region
-variable region


I know that’s a lot but I virtually have no idea about any of those things. The full extent of my knowledge is, like, an antibody will bind with a specific antigen and agglutinate and immobilise it to allow other cells like T cells to destroy it 

[Scribe]

Could someone explain question 5a of the 2018 NHT exam? I'm reading the examiner's report and it does not make sense to me. Why does the recruitment of healthy T helper cells "decrease the number of T helper cells as cell death occurs"?
Thanks!

[PhoenixxFire]

Could somebody please just give me a very simple one sentence description/purpose of each of the following parts of an antibody please... I’ve just been researching it and I don’t think I’m really grasping any info
-Light chain
-Heavy chain
-Heavy chain bridges
-Phagocyte attracting region
-constant region
-variable region


I know that’s a lot but I virtually have no idea about any of those things. The full extent of my knowledge is, like, an antibody will bind with a specific antigen and agglutinate and immobilise it to allow other cells like T cells to destroy it 

You don’t need to be able to define any of them. You just need to be able to draw and label it. Actually, give me a minute and I’ll edit a diagram into this post

diagram (excuse my dodgy drawing skills)

So yeah, so long as you can draw and label that then you’re fine. Could probably do a much simpler version (like I think you’d be fine if you just did a line representing each of the four peptides it’s made of).

Not sure if you actually need to know about the constant and variable regions but it’s pretty simple. The part that changes between antibodies is their binding site, so that’s the variable region. The rest of the antibody is the same so it’s the constant region.

[C14M8S]

Could someone explain question 5a of the 2018 NHT exam? I'm reading the examiner's report and it does not make sense to me. Why does the recruitment of healthy T helper cells "decrease the number of T helper cells as cell death occurs"?
Thanks!

The healthy helper T cells are targets of viral infection and are quickly infected after recruitment, eventually repeating the cycle until there are no healthy T helper cells left.

[vox nihili]

Could someone explain question 5a of the 2018 NHT exam? I'm reading the examiner's report and it does not make sense to me. Why does the recruitment of healthy T helper cells "decrease the number of T helper cells as cell death occurs"?
Thanks!

Because HIV kills T-helper cells

[Azim.m]

Could someone explain question 5a of the 2018 NHT exam? I'm reading the examiner's report and it does not make sense to me. Why does the recruitment of healthy T helper cells "decrease the number of T helper cells as cell death occurs"?
Thanks!

Correct if I’m wrong, but I think they mean...
Since HIV specifically attacks t helper cells, as the number of t helper cells initially increases with recruitment, there is more t helper cells for the virus to infect and kill, hence the low number of t helper cells leads to outcomes mentioned in the examiners report

[randomnobody69420]

A section of a DNA strand has the base sequence AGCGCATAGCAA.
During DNA replication to form the complementary DNA strand, a mutation involving a single base
substitution occurred in the last triplet of this section.
This mutation was then passed on to the mRNA when transcription of the complementary strand occurred.
The base sequence of the mRNA containing the mutation could be
A. AGCGCAUAGCAA
B. AGCGCAUAGUAA
C. UCGCGUAUCGUU
D. UCGCGUAUCAUU

Why is the answer here D? I put B

[EllingtonFeint]

Q 39
The answer is B
But why would there be 3 bands when the sequence is only cut once??

A section of a DNA strand has the base sequence AGCGCATAGCAA.
During DNA replication to form the complementary DNA strand, a mutation involving a single base
substitution occurred in the last triplet of this section.
This mutation was then passed on to the mRNA when transcription of the complementary strand occurred.
The base sequence of the mRNA containing the mutation could be
A. AGCGCAUAGCAA
B. AGCGCAUAGUAA
C. UCGCGUAUCGUU
D. UCGCGUAUCAUU

Why is the answer here D? I put B

It’s in mRNA, so the answer has to have U instead of A
And then it says in the last triplet there was a mutation; GUU would be non mutated cos G is complementary to C, so it would have to be AUU where A was where G should be...

Hope that makes sense 

Mod edit (PF): Merged posts

[PhoenixxFire]

Q 39
The answer is B
But why would there be 3 bands when the sequence is only cut once??

It doesn’t say that the sequence is cut once. Grab some pens and draw on the strand where the two restriction enzymes would cut it and see what you come up with

[EllingtonFeint]

You don’t need to be able to define any of them. You just need to be able to draw and label it. Actually, give me a minute and I’ll edit a diagram into this post

diagram (excuse me dodgy drawing skills)

So yeah, so long as you can draw and label that then you’re fine. Could probably do a much simpler version (like I think you’d be fine if you just did a line representing each of the four peptides it’s made of).

Not sure if you actually need to know about the constant and variable regions but it’s pretty simple. The part that changes between antibodies is their binding site, so that’s the variable region. The rest of the antibody is the same so it’s the constant region.

Ohmigosh thank you

It doesn’t say that the sequence is cut once. Grab some pens and draw on the strand where the two restriction enzymes would cut it and see what you come up with

I still don’t get it though...
So the DNA sequence is chopped into two fragments cos of the AluI,
Then the HindIII recog sequence is broken up so it won’t cut, so what do they mean by three bands??
Mod edit (PF): Merged post

[C14M8S]

1) If you sequence a genome, is it comparative genomics or DNA sequencing?
2) I know with DNA sequencing, you are comparing the similarities and differences in the base sequences of DNA, but with comparative genomics, what are you actually comparing?

I'm asking so many questions These practice exams have revealed many gaps in my knowledge

1) It is DNA sequencing. Comparative genomics is the comparison of genomes.
2) DNA sequencing is taking a DNA sequence, whereas comparative genomics is comparing the genomes of two organisms.

[EllingtonFeint]

RNA polymerase joins RNA nucleotides.
So, does DNA polymerase join DNA nucleotides?

[vox nihili]

RNA polymerase joins RNA nucleotides.
So, does DNA polymerase join DNA nucleotides?

Yes

[PhoenixxFire]

I still don’t get it though...
So the DNA sequence is chopped into two fragments cos of the AluI,
Then the HindIII recog sequence is broken up so it won’t cut, so what do they mean by three bands??

Sorry, I made the silly mistake of assuming company exams are accurate Yeah, I reckon they've screwed up there. With the restriction enzymes in the flow diagram you're going to end up with two fragments.

Edit: Woah, how do you post in 16 seconds Vox

[vox nihili]

Sorry, I made the silly mistake of assuming company exams are accurate Yeah, I reckon they've screwed up there. With the restriction enzymes in the flow diagram you're going to end up with two fragments.

Edit: Woah, how do you post in 16 seconds Vox

Don't worry, you'll get there one day :p