VCE Biology Question Thread

[katiesaliba]

What would be the advantage of restriction enzymes producing sticky ends in recombinant DNA technology than blunt ends?

Thanks!

Sticky ends provide a greater surface area for bonds to occur and DNA to hybridise. Blunt ends can only form covalent, phosphodiester bonds where as sticky ends can form both covalent and hydrogen bonds with a foreign DNA sample. Also, as DNA ligase is needed to anabolise the backbone of DNA, using sticky ends will be quicker too (I guess?) because DNA ligase would work more efficiently (the two DNA strands would have already hybridised due to hydrogen bonds, therefore successful collisions between the enzyme and recombinant DNA would occur more frequently). I've gone a bit chemistry, but that might help clear things up?

Chimpanzees are the closest living relative to modern humans (98% of our genomes are similar). Explain in terms of natural selection,  how the two species diverged
Thank you all

Okay, so firstly you'll need to consider the principles of natural selection:
-variation of phenotypes present within a population (clines; occur by chance) prior to exposure to selection pressure.
-struggle for survival due to selection pressures (abiotic and biotic)
-selective advantage (favourable phenotypes)
-inheritance (individuals with selected phenotypes reproduce, therefore passing on favoured genes to their offspring)
-frequency of selected phenotypes thus increases within a population (microevolution)

So, when answering the question you'll need to address these principles.
An example of an answer may be:
The divergence would have occurred due to their common ancestor inhabiting different areas and therefore exposing itself different selection pressures. Due to the phenotypic variation within the species, different traits would have been selected for in these different environments. The favoured traits would have then been passed on via inheritance, increasing the frequency of their alleles within the population. This example of microevolution would have eventually resulted in speciation when the gene pools of both groups became isolated so that successful interbreeding could not occur.

My answer is verbose ahah but I think it covers the question

[shivaji]

just out of interest - will the exam this year be hard?

[Reus]

just out of interest - will the exam this year be hard?

Harder than last year I've heard. However you could perceive it as a good thing tbh

[ValiantIntellectual]

I know this is a bit irrelevant but is anyone truly aiming for the fifty?

[Reus]

I know this is a bit irrelevant but is anyone truly aiming for the fifty?

I am  ! But I feel like I'll drop marks inevitably to be honest so 40+

[millie96]

Are features of xylem and phloem cells still examinable?

[anat0my]

Are features of xylem and phloem cells still examinable?

No, but it's worth knowing that plant hormones travel through the vascular system (xylem & phloem) whereas animal hormones travel through the blood stream.

[millie96]

Thanks!

Also I got this question on a practice paper, can somebody please explain how this is the answer?

Q: A polypeptide found in the cytoplasm of a cell contains 30 amino acids. How many nucleotides would be required in mRNA for this polypeptide to be translated?
A: 93

[Reus]

Thanks!

Also I got this question on a practice paper, can somebody please explain how this is the answer?

Q: A polypeptide found in the cytoplasm of a cell contains 30 amino acids. How many nucleotides would be required in mRNA for this polypeptide to be translated?
A: 93

Well one amino acid is complementary to 3 nucleotides. Therefore 30x3 is 90 amino acids. Since this is a polypeptide, it means there is a stop codon, which also is coded for by an additional 3 nucleotides. 90+3+93. So all in all, there are 93 nucleotides in this polypeptide.

[vox nihili]

Thanks!

Also I got this question on a practice paper, can somebody please explain how this is the answer?

Q: A polypeptide found in the cytoplasm of a cell contains 30 amino acids. How many nucleotides would be required in mRNA for this polypeptide to be translated?
A: 93

These questions are ridiculously silly as they completely miss the fact that the mature mRNA has quite a lot of extra nucleotides like the poly-A tail or the 5' methylated cap (which actually happens to be a nucleotide). They're perhaps even too simplistic for year twelve students. /rantover

[dankfrank420]

Can someone explain in bullet points what happens in the light- dependant, light independant photosynthesis, as well as the Electron Transport chain.

[howlingwisdom]

What would be the advantage of investigating mutation rates in mtDNA rather than nuclear DNA?

[vox nihili]

What would be the advantage of investigating mutation rates in mtDNA rather than nuclear DNA?

Slower mutation rate

[shivaji]

does cytokinesis occur at the end of meiosis 1?

[melons]

What would be the advantage of investigating mutation rates in mtDNA rather than nuclear DNA?

It doesn't undergo recombination so is easier to trace.