VCE Biology Question Thread

[Apink!]

Hi all,

this is the question I'm having trouble with. I know that in a human somatic cell, there is 46 chromosomes. But does 1 chromosome = 1 molecule of DNA? I'm very confused. The correct answer is 46

[plsbegentle]

Hi all,

this is the question I'm having trouble with. I know that in a human somatic cell, there is 46 chromosomes. But does 1 chromosome = 1 molecule of DNA? I'm very confused. The correct answer is 46

You are right, 1 chromosome = 1 Molecule of DNA. G1 should have 46 chromosomes, however in the S stage there should be 92.

[Apink!]

You are right, 1 chromosome = 1 Molecule of DNA. G1 should have 46 chromosomes, however in the S stage there should be 92.

Thank you so much plsbegentle!

[vox nihili]

I have seen questions define molecule differently in the context of DNA. The definition of molecule and as it applies to DNA is somewhat fluid, so if you wrote 92 I wouldn't be too concerned.

[zsteve]

I have seen questions define molecule differently in the context of DNA. The definition of molecule and as it applies to DNA is somewhat fluid, so if you wrote 92 I wouldn't be too concerned.

Yeah, looks like 1 molecule of DNA = 2 strands, even though from a chemical sense they're two molecules which are just closely associated by H-bonding.

I was confused for some time before I was enlightened

[Apink!]

Hi all,

I have another question. I've attached the original question and the answers. In the answers, it says that  if the alleles were independently inherited, the phenotype ratio would be 1:1:1:1. I don't really understand this. If I perform a dihybrid cross (the parents being heterozygrous) I get the phenotype ratio of 9:3:3:1 not 1:1:1:1.

Thank you so much everyone

[vox nihili]

Hi all,

I have another question. I've attached the original question and the answers. In the answers, it says that  if the alleles were independently inherited, the phenotype ratio would be 1:1:1:1. I don't really understand this. If I perform a dihybrid cross (the parents being heterozygrous) I get the phenotype ratio of 9:3:3:1 not 1:1:1:1.

Thank you so much everyone

Question didn't attach

[Apink!]

omg that's stupid

*facepalm

edit: ATTACHED!

[plsbegentle]

Hi all,

I have another question. I've attached the original question and the answers. In the answers, it says that  if the alleles were independently inherited, the phenotype ratio would be 1:1:1:1. I don't really understand this. If I perform a dihybrid cross (the parents being heterozygous) I get the phenotype ratio of 9:3:3:1 not 1:1:1:1.

Thank you so much everyone

Its a test cross! A test cross means that it will be homozygous recessive. So ill just show u how to work it out, just in case

Let hetrozgous brown fly with long wings be: BbAa
Let the test cross fly be: bbaa
Set up punnet square
     BA     Ba     bA     ba
ba BbAa Bbaa bbAa bbaa

phenotypic ratio is 1;1;1;1
 If the genes are linked, then it would be 1:1 because they cant be independently assorted since they are on the same chromosome.
hope that helps

[Apink!]

Thank you plsbegentle!!


Can someone translate this question into English? ...


Thank you all

[vox nihili]

Thank you plsbegentle!!


Can someone translate this question into English? ...


Thank you all

Not relevant to VCE, so just skip it.


Basically all it's telling you is that because there are two X chromosomes and we only need one, in each cell, one X chromosome is randomly turned off, so it basically sits there and does nothing. So the particular colour fur you get depends on which X chromosome is turned off in the cells producing that fur.

That's an over-simplification, and there's a lot of nuance here that we could go into, but it's all completely irrelevant to the VCE course so I'd just move on

[blacksanta62]

Hey guys, would this be a suitable explanation for the attached question and is it the correct choice/explanation:
Summary
G1 - 1 protein affected
G2 - many proteins affected
Answer
G2 is more likely to code for tRNA. tRNA has molecular specificity and if the gene which codes for it is mutated ==> tRNA is affected and we lose an anti-codon which would bind to a mRNA codon, affecting the polypeptide chain which is normally synthesised. Therefore we affect a large number of proteins.

Thank you

[vox nihili]

Hey guys, would this be a suitable explanation for the attached question and is it the correct choice/explanation:
Summary
G1 - 1 protein affected
G2 - many proteins affected
Answer
G2 is more likely to code for tRNA. tRNA has molecular specificity and if the gene which codes for it is mutated ==> tRNA is affected and we lose an anti-codon which would bind to a mRNA codon, affecting the polypeptide chain which is normally synthesised. Therefore we affect a large number of proteins.

Thank you

Hmmm, it actually sounds like you're implying that the tRNA is specific to one gene. Your talk about "molecular specificity" kind of throws you off track.

My answer:

Mutation of G2 disrupts protein expression globally. tRNAs are used in the expression of all proteins. Therefore, G2 is more likely to code for tRNA than G1. G1 can be excluded as mutation thereof only disrupts the expression of one protein.

Keep it simple. Show the link between the two things and make sure to talk about why you can exclude the other option in cases like this.

[blacksanta62]

Maybe I'm misunderstanding the first part of your explanation but are tRNAs coded for by more than one gene? Is that what you mean? The rest makes sense though. And I'll make sure to keep them to the point in the future.
Thank you

[vox nihili]

Maybe I'm misunderstanding the first part of your explanation but are tRNAs coded for by more than one gene? Is that what you mean? The rest makes sense though. And I'll make sure to keep them to the point in the future.
Thank you

Yep, tRNAs are coded for by more than one gene (there are 64 different tRNAs so it follows that there should be at least 64 tRNA genes). But losing any one of those 64 tRNAs will disrupt protein expression.