VCE Biology Question Thread

[cosine]

The answer is C. Phenotype = genotype interaction with the environment. The trait is controlled by one gene only so how is it polygenic

Where does it say that it is controlled by one gene only?

[Biology24123]

Do nonsense mutations include frameshift mutations or are they just mutations coding for stop codons

[BakedDwarf]

Do nonsense mutations include frameshift mutations or are they just mutations coding for stop codons

A non-sense mutation, by definition, is a mutation that results in a stop codon being produced. This could result directly from a substitution mutation or indirectly by a frameshift mutation.

[Biology24123]

So frameshift mutations could technically be regarded as non-sense?

[vox nihili]

for the attached, when do we know to start a fresh punnet square to work out the probability, as opposed to use the probability from the co-existing offspring?

You should never, ever, ever use the other offspring to calculate a probability.

So frameshift mutations could technically be regarded as non-sense?

Yes and no. They do have the same effect. Nonsense mutations induce early stop codons by substitution, whereas frameshift mutations shift the reading frame of the gene (in other words, if a sequence is read ATC-GGC-ATC-GCC a frameshift might make this same sequence read A-TCG-GCA-TCG-CC. This induces an early stop codon because stop codons occur randomly relatively frequently.

[cosine]

You should never, ever, ever use the other offspring to calculate a probability.

Yes and no. They do have the same effect. Nonsense mutations induce early stop codons by substitution, whereas frameshift mutations shift the reading frame of the gene (in other words, if a sequence is read ATC-GGC-ATC-GCC a frameshift might make this same sequence read A-TCG-GCA-TCG-CC. This induces an early stop codon because stop codons occur randomly relatively frequently.

That was from a VCAA paper, 2003 exam 2, so is it their mistake? Got it though, never use other offspring to calculate probability. Would you be able to enlighten me about the other questions above? Not gonna lie, was waiting for you anyway xD

Many thanks

[Biology24123]

That was from a VCAA paper, 2003 exam 2, so is it their mistake? Got it though, never use other offspring to calculate probability. Would you be able to enlighten me about the other questions above? Not gonna lie, was waiting for you anyway xD

Many thanks

You didn't attach anything for a few of your questions

[vox nihili]

That was from a VCAA paper, 2003 exam 2, so is it their mistake? Got it though, never use other offspring to calculate probability. Would you be able to enlighten me about the other questions above? Not gonna lie, was waiting for you anyway xD

Many thanks

Hmmm if they told you to use the other offspring, then yes. It can give a vague idea, but it's not reliable as a means of calculating probability unless you have a shit tonne of offspring.

I'll let the others have a crack first and then moderate if need be

[Biology24123]

two questions for the attached: (14)

1. you see how they give us the amino acid sequence, do we assume that the corresponding DNA sequences for those amino acid sequences were all exon regions on the actual DNA molecule in the nucleus?

2. why is B incorrect? I cannot make out why, because deleting the 12 nucleotide will result in the change of the fourth amino acid, am i missing something?

Thymine is removed (12) so that means the new amino acid cannot be Thr as only Thr has thymine as the first base in the DNA triplet

[adnauseam]

are we allowed to say recessive alleles and dominant alleles?
Or do we stick to allele coding for recessive phenotype etc?
Thanks

[cosine]

Thymine is removed (12) so that means the new amino acid cannot be Thr as only Thr has thymine as the first base in the DNA triplet

Exactly then should not B also be correct?
Also can you answer the question 1: you see how they give us the amino acid sequence, do we assume that the corresponding DNA sequences for those amino acid sequences were all exon regions on the actual DNA molecule in the nucleus?

[sushibun]

two questions for the attached: (14)

1. you see how they give us the amino acid sequence, do we assume that the corresponding DNA sequences for those amino acid sequences were all exon regions on the actual DNA molecule in the nucleus?

2. why is B incorrect? I cannot make out why, because deleting the 12 nucleotide will result in the change of the fourth amino acid, am i missing something?

1. I would assume so. The amino acids have already been coded for from mRNA. The mRNA would have to have had the introns removed thus leaving the exons. So the DNA sequences corresponding to the amino acid must be exons. Correct me if I'm wrong.

2. B would cause a frameshift mutation from 12 nucleotide thus affect the whole DNA sequence after it, so not only the fourth amino acid would be affected but also all the amino acids after. I guess it's true that the fourth amino acid would be affected but to VCAA A was the more correct answer

[Biology24123]

are we allowed to say recessive alleles and dominant alleles?
Or do we stick to allele coding for recessive phenotype etc?
Thanks

Never say dominant/recessive allele

[Biology24123]

Exactly then should not B also be correct?
Also can you answer the question 1: you see how they give us the amino acid sequence, do we assume that the corresponding DNA sequences for those amino acid sequences were all exon regions on the actual DNA molecule in the nucleus?

Oh. Thought you meant why it is correct.

[cosine]

1. I would assume so. The amino acids have already been coded for from mRNA. The mRNA would have to have had the introns removed thus leaving the exons. So the DNA sequences corresponding to the amino acid must be exons. Correct me if I'm wrong.

2. B would cause a frameshift mutation from 12 nucleotide thus affect the whole DNA sequence after it, so not only the fourth amino acid would be affected but also all the amino acids after. I guess it's true that the fourth amino acid would be affected but to VCAA A was the more correct answer

So B technically is correct?

And for the first question, I may have not been clear in what my question was. The primary structure of haemoglobin is given, and the mRNA codons will be exactly that of the amino acid sequence codons. However, the mRNA codons would not necessarily reflect the exact nucleotide sequence of the DNA molecule because the introns would have been removed. You see how question 14 is asking about the DNA molecule, do we have to assume that the DNA molecule transcripted the mRNA molecule with no introns? Because what might be the 12th nucleotide in the DNA molecule may be something else in the mRNA codon sequence, because the introns would have been removed?