Biology Unit 4 Questions Megathread

[WhoTookMyUsername]

Thanks lexitu
11)
Lets say there are 2 genes coding for non - identical amino acids, perhaps differing by one amino acid substitution for another similar amino acid, which results in little discernible change in phenotype; are these regarded as different alleles as they code for different proteins?

[lexitu]

You still have me a bit confused - if they are two genes then they have different loci and you have to consider them separately because alleles are different forms of the same gene.

If you are talking about the same gene having some very mildly alternate forms then yes, they are still alleles, however small the difference is because they code for a different polypeptide.

[WhoTookMyUsername]

yep that's what i was talking about

elementary mistake...
a mistake like that cost me a mark on midyears

[scar]

Hi Bazza,

Q2  Anuploidy normally doesn't result in fertile offspring in animals (though I do seem to remember a question about a frog..)  It happens quite often in plants though.  Tetraploidy  (4 copies of the chromosomes) allows matching pairs to be created in Mitosis and therefore can create viable sex cells.

10.  Yes the fruit is the 'womb' and will taste according to whatever DNA the 'mother' plant is carrying.  The seeds may be quite different though - you might grow a tree from one of the seeds and find it is quite bitter.

11.  Different alleles don't necessarily change the phenotype of an organism.  Eg.  STR's used in DNA profiling have different versions so are called alleles but are on non coding regions of DNA so don't change the phenotype..  Hmm Maybe they should call them 'alleles' since they are not part of a functioning gene.

[lexitu]

Hi Bazza,

Q2  Anuploidy normally doesn't result in fertile offspring in animals (though I do seem to remember a question about a frog..)  It happens quite often in plants though.  Tetraploidy  (4 copies of the chromosomes) allows matching pairs to be created in Mitosis and therefore can create viable sex cells.

10.  Yes the fruit is the 'womb' and will taste according to whatever DNA the 'mother' plant is carrying.  The seeds may be quite different though - you might grow a tree from one of the seeds and find it is quite bitter.

Just on Q2 - tetraploidy is not an aneuploidy but rather a polyploidy.

And fruits normally contain plenty of sugar which is the main thing that gives them their usually sweet taste - the goal is for an animal (often) to eat them and the assist in seed dispersal.

[WhoTookMyUsername]

Thanks for the help

1) does VCAA regards A. Africanus as the ancestor of Homo sapiens or P. Robustus ?
3) Do plants usually have sex chromosomes? And do those without tend to self fertilise?
4) Can a population bottleneck NOT arising from chance still be referred to as such?
If so, are there two types of population bottlenecks, only one of which refers to genetic drift?
5) Can genetic isolation refer to genetic isolation at that point in time (e.g. when seperated geographically?)
6) Are anticodons read in 3'->5' or 5'->3' end by convention?
7) Do prokaryotes have non - coding regions? i have notes saying NO, but if you think about it, the region between the promoter and the genes in an operon must be "non coding".... ?
8)is DNA hybridisation usually done with cDNA & cDNA


ADDITIONAL QUESTIONS
9) Can GMO refer to TGO (i'm pretty sure it can but i have a couple of sources saying not)
10) Can plasmids be used to introduce DNA to plants? Is this how Agrobacterium Tunificus or something works or does A. Tunificus somehow... integrate its plasmid into chromosomal DNA?

[Russ]

3) Do plants usually have sex chromosomes? And do those without tend to self fertilise?

This is coming from me, so take it with a grain of salt, but from memory the majority don't. Only time they do is when they're hermaphroditic.

4) Can a population bottleneck NOT arising from chance still be referred to as such?
If so, are there two types of population bottlenecks, only one of which refers to genetic drift?

Bottleneck just refers to the narrowing of the gene pool etc. and it can be from natural or artificial factors. If you want to specific in a question, you can but there's no term for it afaik.

6) Are anticodons read in 3'->5' or 5'->3' end by convention?

What do you mean "read"? Nothing reads them per se, they pair up with the codon?

7) Do prokaryotes have non - coding regions? i have notes saying NO, but if you think about it, the region between the promoter and the genes in an operon must be "non coding".... ?

Yes, absolutely, what notes do you have that say no?

8)is DNA hybridisation usually done with cDNA & cDNA

DNA hybridisation is done with linear DNA, you can't use circular DNA for it. You just use short fragments that are complementary to the gene/region of interest

9) Can GMO refer to TGO (i'm pretty sure it can but i have a couple of sources saying not)
10) Can plasmids be used to introduce DNA to plants? Is this how Agrobacterium Tunificus or something works or does A. Tunificus somehow... integrate its plasmid into chromosomal DNA?

Yes/yes

[WhoTookMyUsername]

Thanks Russ, been missing your awesome help for while now, hope uni isn't too busy ( though I've had lex answering most of my conunndrums, as well as ssome help from scar and others

Clafifying your answer to 3) I thought no sex chromosomes would be present in hermaphrodites as chromosomes would not differ between sexes?

B read I mean how to represent them on paper

E.g. If a question states, what is the anticodon (  there is a diagram) do I give it in 5-> 3 or vice versa

Notes I have are from teacher who is usually correct.
Thanks for your help

[Russ]

Yeah cheers, it has been unfortunately

3 - I think I was referring to the self fertilization thing there. Best to wait for someone else, I'm remembering class from year 11 here

5 - 3' -> 5' is probably best so you can see the matching but I don't think it matters as long as you specify

Your teacher is probably using "non coding region" to refer just to introns/exons which isn't the full meaning of the word as far as I'm concerned

[WhoTookMyUsername]

wouldn't the region between the promoter and start of gene still be an "intron"
as it is transcribed but not translated?


Thanks russ!@

[Mr. Study]

Just a question from the VCAA 2006 exam. 5 c)

For each region of DNA there are two values, for example, 164/164. Suggest a reason for this.

Can someone explain to me why there are two numbers? I read the assessors report and it is confusing.

[lexitu]

Because there are two alleles - two copies of that region - one from each chromosome in the pair. (I'm just answering this from memory of what the question is asking).

[Mr. Study]

Ahhh!

Thank you! That makes everything understandable.

[Kaille]

What is the purpose of a back cross?

What is the importance of the difference between microsatellites and minisatellites in relation to dna fingerprinting and dna profiling? :S

thanks

[Mr. Study]

Just a few questions.

1. What exactly is an Anti-Codon and What is it's purpose?
2. Can someone explain what is independent assortment and what happens during it?
3. An explanation on DNA Hybridisation.
4. What is  Chismata Formation?

Thank you!