VCE Biology Question Thread

[chickennugget]

IgM can't cross the placenta, so it has to have been produced by the baby. If the baby is producing anti-rubella IgM, then it has to have been infected by the virus in utero, because it would only produce such antibodies if it were exposed.
Tricky question. I'm sure it was poorly answered by most?

Agglutination just means that the red blood cells clump together because they've been bound by antibodies.

Someone with type O blood has antibodies to A and B
Someone with type A has antibodies to B
Someone with type B has antibodies to A
Someone with type AB has antibodies to no other blood group

Just to be sure, the O antigen isn't really in itself an antigen. O refers to the absence of A or B antigens on the surface of blood cells*

So if you added B antibodies to AB blood, that would bind the B antigen in that blood, which would agglutinate. If you added antibodies of type A to type O blood, what would it bind? There's no A antigen there.


*Beyond VCE: for the pedants: O blood type does technically have the H-antigen, but that just complicates the explanation

Thanks
Just with the rubella question, wouldn't passive immunity be obtained via breast milk? Because for the child to have gotten rubella, wouldn't the mother have to have had been infected? Is the only reason (B) is wrong because 2 years is too long to be breast-fed?

[vox nihili]

Thanks
Just with the rubella question, wouldn't passive immunity be obtained via breast milk? Because for the child to have gotten rubella, wouldn't the mother have to have had been infected? Is the only reason (B) is wrong because 2 years is too long to be breast-fed?

The question says newborns before being fed. As the say, always have to read the question carefully! :p

[psyxwar]

Thanks
Just with the rubella question, wouldn't passive immunity be obtained via breast milk? Because for the child to have gotten rubella, wouldn't the mother have to have had been infected? Is the only reason (B) is wrong because 2 years is too long to be breast-fed?

And just on that note you only get natural passive immunity for about 6 months, regardless of how long you breastfeed the child

[vox nihili]

And just on that note you only get natural passive immunity for about 6 months, regardless of how long you breastfeed the child

There's a blast from the past! Glad to see you back

[psyxwar]

There's a blast from the past! Glad to see you back

Thanks haha, just doing some pre-exam procrastination

[gameboy99]

Hey guys I am a bit confused with cell mediated and humoural immunity. I understand the two different processes but still not clear when each process is used for a specific situation. Could someone give an example of a specific situation where cell mediated immunity takes places and another situation were humoural immunity takes place.
Thanks 

[vox nihili]

Hey guys I am a bit confused with cell mediated and humoural immunity. I understand the two different processes but still not clear when each process is used for a specific situation. Could someone give an example of a specific situation where cell mediated immunity takes places and another situation were humoural immunity takes place.
Thanks 

The reality is that you really get both at the same time. For instance, T-helper cells are needed to "help" the humoral response happen. There are a couple of specifics when you'd expect one to predominate, however:

viral infections tend to elicit a stronger cellular response (because cytotoxic T-cells are needed to kill the intracellular virus), bacterial infections often provoke a stronger antibody response.

[The Usual Student]

Hey guys, what is the reasons ALL cells need to have the same DNA?
Like I get how they have the same DNA and that only certain genes are expressed specific to the cells function,
But why do all cells need the EXACT DNA even though only a portion will be expressed?

[plsbegentle]

Did anyone else do the stav midyear exam? if so, how did u go? 

[vox nihili]

Hey guys, what is the reasons ALL cells need to have the same DNA?
Like I get how they have the same DNA and that only certain genes are expressed specific to the cells function,
But why do all cells need the EXACT DNA even though only a portion will be expressed?

Well they don't really need it, do they?

It just provides an easy way to set things up, and also provides some flexibility. By having all the entire genome, the cell can express any gene if it needs it. In many cases cells will actually undergo a complete phenotypic change and become completely different cells. In this context, the cell does need to express completely different genes, an option that wouldn't be open to it if it only had a limited genome.

[undefined]

Hi all,

I'm not doing VCE Biology right now however I'm unsure on a topic related to it. How does protein synthesis work within a cell and how is mRNA, tRNA and rRNA associated with it?

Thanks!

[vox nihili]

Hi all,

I'm not doing VCE Biology right now however I'm unsure on a topic related to it. How does protein synthesis work within a cell and how is mRNA, tRNA and rRNA associated with it?

Thanks!

Gonna sit out on this one and encourage someone who's currently doing Bio to answer. Will fill in any gaps, so give it a shot

[The Usual Student]

Why is it advantageous for there to be multiple chromosomes opposed to one big chromosome during cell divsion?
Is it easier to replicate? idk really

[HasibA]

Did anyone else do the stav midyear exam? if so, how did u go? 

yeah buddy, had the STAV 2016 one, didn't worry about studying for it too much  but got 93% so pretty pleased, was of decent difficulty, hbu? (cohort average was really low but, like 60%)

[The Usual Student]

sorry to double post but also
Why is it advantageous for multiple different types of proteins to be involved in dna replication? This is practice sac question and it is really confusing