VCE Biology Question Thread

[cosine]

How would we then distinguish telophase? I thought that by using a plasma membrane strain, we can observe the two different groups of nuclei that are contained within one cell. And I don't think the nuclear membrane would help with this because it would just appear as two different nuclei in two different cells.

Think about it - if you view two cells separately, then that would be cytokinesis, and that it not part of mitosis. But if we stain the nuclear membrane, it will indicate to us when the two membranes reform around the sets of chromosomes.

[cosine]

May someone explain the concept of homozygous, heterozygous, homozygote, heterozygote?

[grannysmith]

May someone explain the concept of homozygous, heterozygous, homozygote, heterozygote?

When we're talking about a particular gene locus, a homozygous individual (homozygote) has identical alleles whereas a heterozygous individual (heterozygote) has non-identical alleles. For example: AA and Aa, respectively.

[Biology24123]

Do we need to know about the properties of specific secondary structures (e.g a helix)

[cosine]

Do we need to know about the properties of specific secondary structures (e.g a helix)

Proteins? Most definitely yes:

The secondary structure of proteins is a result of the hydrogen bonding between functional groups of separate amino acids within the peptide chain, essentially forming  two structures:
- Alpha helices, and
- Beta pleated sheets

[vox nihili]

Do we need to know about the properties of specific secondary structures (e.g a helix)

You need to know what the secondary structures are (i.e. alpha-helices, beta-sheets and random coils). Beyond that, you don't need to know anything about them.

Proteins? Most definitely yes:

The secondary structure of proteins is a result of the hydrogen bonding between functional groups of separate amino acids within the peptide chain, essentially forming  two structures:
- Alpha helices, and
- Beta pleated sheets

This is beyond the VCE course: saying functional groups is too vague and is really just stating the obvious. Secondary structures are formed by hydrogen bonding between the carboxyl and amino groups in the polypeptide backbone. Tertiary structure, on the other hand, is driven by bonding between R-groups.

[cosine]

You need to know what the secondary structures are (i.e. alpha-helices, beta-sheets and random coils). Beyond that, you don't need to know anything about them.

This is beyond the VCE course: saying functional groups is too vague and is really just stating the obvious. Secondary structures are formed by hydrogen bonding between the carboxyl and amino groups in the polypeptide backbone. Tertiary structure, on the other hand, is driven by bonding between R-groups.

I thought functional group means carboxyl and amino groups?
And if it's beyond the scope of VCE, is my definition correct or not for VCE ?

[cosine]

Few questions about hereditary:

1). What is the main difference between codominant inheritance and intermediate inheritance?

2). Why is it that in codominant inheritance, both alleles are dominant and so they are both expressed. But why do they not 'overlap' each other?  (red+white = pink).

3). Why is it that in intermediate inheritance, both alleles are recessive, but how come they overlap each other and are not expressed as the codominant traits?

4). How can red blood cells contain multiple alleles if they don't even have a nucleus, and hence no chromosomes?
 

[vox nihili]

I thought functional group means carboxyl and amino groups?
And if it's beyond the scope of VCE, is my definition correct or not for VCE ?

Carboxyl and amino groups are indeed functional groups; however, there are also plenty of other functional groups on amino acids, particularly those on the side chains.
All you need to say about secondary structure is that it includes alpha-helices, beta-sheets and random coils.

Few questions about hereditary:

1). What is the main difference between codominant inheritance and intermediate inheritance?

2). Why is it that in codominant inheritance, both alleles are dominant and so they are both expressed. But why do they not 'overlap' each other?  (red+white = pink).

3). Why is it that in intermediate inheritance, both alleles are recessive, but how come they overlap each other and are not expressed as the codominant traits?

4). How can red blood cells contain multiple alleles if they don't even have a nucleus, and hence no chromosomes?
 

1. Based on your subsequent questions, I think you already know the answer to this. Codominance refers to the situation wherein both traits are expressed simultaneously in the heterozygous condition; whereas incomplete dominance refers to the situation wherein the heterozygote is distinct from the homozygous recessive and homozygous dominant (i.e. the combination of two distinct alleles gives rise to a trait that otherwise does not occur).

2/3. It's just the nature of those particular traits. You don't really need to know why that's the case. You just need to know that some traits will behave that way, though not need to have an answer as to why they do.

4. In the early stages of their development, red blood cells do have nuclei (they have to otherwise how do they develop?). The nucleus is lost during late development.

[Biology24123]

Currently doing practice exams and getting about 75-85%. How can I improve to get 90+

[heids]

Currently doing practice exams and getting about 75-85%. How can I improve to get 90+

Said it a thousand times before, but: what are you doing wrong?  Where you do lose marks?  There is no 'quick fix' we can tell you.  It just takes work.  If you don't know the theory well enough, then you won't improve until you've learnt it.  If it's not that, then what is it?  Focus on never making a mistake twice.  If you want our help, tell us specifics

(Admire my forbearance in disregarding another opportunity to get on my anti-commercial-exams hobby horse.)

[cosine]

Carboxyl and amino groups are indeed functional groups; however, there are also plenty of other functional groups on amino acids, particularly those on the side chains.
All you need to say about secondary structure is that it includes alpha-helices, beta-sheets and random coils.

1. Based on your subsequent questions, I think you already know the answer to this. Codominance refers to the situation wherein both traits are expressed simultaneously in the heterozygous condition; whereas incomplete dominance refers to the situation wherein the heterozygote is distinct from the homozygous recessive and homozygous dominant (i.e. the combination of two distinct alleles gives rise to a trait that otherwise does not occur).

Thank you for your answer, Mr. T-Rav.

Would it suffice to describe secondary structured proteins as "Hydrogen bonding between the functional groups, carboxyl and amine, between separate amino acids in a polypeptide chain, which result in the formation of alpha helices, beta pleated sheets and random coils"

Could you also elaborate on the part I bolded from your explanation? I don't quite understand it.

Also does homozygous and heterozygous just refer to the different alleles, right? (If so, does homozygote just mean the organism that has different alleles for the gene?).

Thank you

[heids]

Would it suffice to describe secondary structured proteins as "Hydrogen bonding between the functional groups, carboxyl and amine, between separate amino acids in a polypeptide chain, which result in the formation of alpha helices, beta pleated sheets and random coils"

Probably, but here's the VCAA explanation that'd get full marks and is much easier to remember: 'the coiled or pleated structure within the chain'.  (though yes, know basically what beta-pleated sheets, alpha helices and random loops are)  Basically, it's 'local' folding within the chain, rather than folding of the entire chain.

Could you also elaborate on the part I bolded from your explanation? I don't quite understand it.

Also does homozygous and heterozygous just refer to the different alleles, right? (If so, does homozygote just mean the organism that has different alleles for the gene?).

Homozygous = both alleles the same. (so a homozygote is just an organism with two alleles the same at a particular locus).
Heterozygous = the two alleles are different.

All T-Rav means is that incomplete dominance is that a heterozygous organism (two different alleles) 'shows' them both to some extent, in other words, will have a different phenotype to those with HoD or HoR, whereas with a normal trait, the heterozygote has the same phenotype as a HoD.  Note, this is out of the current study design.

[vox nihili]

Thank you for your answer, Mr. T-Rav.

Would it suffice to describe secondary structured proteins as "Hydrogen bonding between the functional groups, carboxyl and amine, between separate amino acids in a polypeptide chain, which result in the formation of alpha helices, beta pleated sheets and random coils"

Could you also elaborate on the part I bolded from your explanation? I don't quite understand it.

Also does homozygous and heterozygous just refer to the different alleles, right? (If so, does homozygote just mean the organism that has different alleles for the gene?).

Thank you

The reason that's still not correct is because some amino acid side chains have amine and carboxyl groups and these groups are not involved in the secondary structure. For VCE, the definition I gave above will suffice: secondary structure describes alpha-helices, beta-sheets and random coils. You don't need to know the Chemistry behind it.

Beyond VCE: as I alluded to above, secondary structure involves the hydrogen bonding between the carbonyl and amide groups of the polypeptide backbone. Any carboxyl, carbonyl, amide or amino groups in amino acid residue R-groups are not involved in secondary structures. Tertiary structure, on the other hand, involves bonding between R-groups (and some other things but that's well and truly beyond the scope of the VCE course).
 

[paper-back]

What does increased fluidity (through the addition of lipids) actually mean for a cell?