Biology Unit 4 Questions Megathread

[WhoTookMyUsername]

Thanks lexitu! anyone happen know the answer to the second part of the third question and the fourth question?


2 more questions
1) is there any way to completely 100% prove that a trait is x linked?

2) di we have to consider y linkage and disproving it according to vcaa?

[Russ]

1 - Yes but pedigree analysis is sufficient for your purposes
2 - Maybe, but it's not exactly hard to prove/disprove

[lexitu]

2 -  "sex-linked inheritance" is mentioned in the study guide so I would say it's something that could be examined and as Russ said. When reasoning for a trait, I wouldn't disprove it though - will take up space and I don't think it's something that they expect.

[WhoTookMyUsername]

Thanks lexitu and Russ
I meant through pedigree analysis - is the only way to "prove" x linked by saying that more male affected by female and it's most likely x linked?


Anyone know how many centrosomes in a dividing cell ?

[jane1234]

Thanks lexitu and Russ
I meant through pedigree analysis - is the only way to "prove" x linked by saying that more male affected by female and it's most likely x linked?


Anyone know how many centrosomes in a dividing cell ?

You can look at the relationships between parent to child in most cases. If a pedigree shows a dominant trait and a father does NOT pass the trait to ALL of his daughters - then it cannot be sex-linked. Similarly, if it is a resessive trait and a mother with the trait does not pass it to ALL of her sons then you can assume it is not sex-linked.

EDIT: So you can prove if something is NOT sex-linked, but essentially you can't prove it is as autosomal inheritance could follow the same pattern by random chance. But it's very unlikely it would follow the exact pattern of all mothers with a recessive trait passing it on to ALL of her sons so in that case you can assume it's sex linked...

[Russ]

If you have a large enough pedigree then the difference (between "proof" and "almost proof") is statistically negligible

[lexitu]

Yeah, you are just choosing the most likely possibility, in most cases you can eliminate some options, but then you'll find out that nothing can really be proven unless it's over a massive pedigree because sometimes people with allelic combinations that should result in the trait don't end up having it.

But when I answered your question originally, I meant in my opinion there's no need to justify why it's not Y-linked - you can check suggested responses from past VCAA exams to clarify that. Basically, you do whatever it takes to show the examiner you know what you're talking about and no more.

[WhoTookMyUsername]

Thanks for all the advice, just making sure i hadn't overseen some way of 'proving'. But if VCAA doens't mind then it doesn't concern me.
Lexitu - i just saw in a few notes that they refered to Y linked so i was a bit confused about whether we need to disprove that, haven't looked at practice exams yet (will start in a week) so i'll get around to it eventually XD

Does anyone know how many centrosomes in a dividing cell ? (my teacher says 2 and i agree with him, yet lots of other sources say 1 with centrioles splitting up in meiosis/mitosis)
- (are centrioles in themselves considered fully functional organelles?)

Thanks!

[Russ]

i just saw in a few notes that they refered to Y linked so i was a bit confused about whether we need to disprove that

Y linked is the easiest to disprove, since it's dominant and is always and only passed father-son

[WhoTookMyUsername]

Thanks Russ, yeah it's definitely simple, but as Lexitu said i don't want to right it if i don't need to

Sorry to keep repeating this question - but questions do tend to get lost if not answered immediatly and this question is frustrating me (if people don't know that's fine)

1) Does anyone know how many centrosomes in a dividing cell ? (my teacher says 2 and i agree with him, yet lots of other sources say 1 with centrioles splitting up in meiosis/mitosis)
- (are centrioles in themselves considered fully functional organelles?)

2) Can a "germline mutation" refer to mutations in gametes, or is more accurate to refer to mutations in germline cells? I'm messed up with my definitions here
Some sources seem to include gametes in the "germline" yet other's don't...

EDIT:

Q3) Again, my definitions (from various sources are conflicting!!!)
Teacher, my trustworthy (usually) henderson's dictionary of biology, and tutor notes (that i bought - i don't go tutor so can't ask him) all say a point mutation is a SUBSTITUTION

but a few other sources
Insight, Merriam Webster dictionary -

say a point mutation includes addition, substitution and deletion...

Which is right?
thanks

[Mr. Study]

Bazza: I could've sworn a point mutation was Addition, Substitution and Deletion. My notes say it is. (Don't really know how reliable though xD)
(Sorry if I couldn't be of any help)

My questions:

1. What is the process for gene transformation/delivery?
    (I think delivery was through vectors but I need confirmation)
2. What the hell is the conservation of genes?!
3. How are organisms cloned?

[Russ]

The typical usage of point mutation is for a substitution mutation, but since the definition is basically "a point of difference" it can be addition or deletion.

nfi on the centrosomes/centrioles stuff, i forgot that back in 1st year lol

a mutation in germline cells will result in a mutation in gametes, so they're pretty interchangeable. ultimately the mutation has to be in the gamete for it to be passed on i guess. i suppose you could also get spontaneous mutation during the last round of meiotic division, which would mean it was only in the gamete.

genetic transformation has a bunch of processes, the most common one used in a lab is probably plasmid based

gene conservation has a few meanings, most likely is the fact that the more conserved a gene is (the more species etc. have it), the more important it is. the genes encoding your tRNAs are incredibly highly conserved, because they're so fundamental. an example of this is in bacteria, where plasmids often insert via redundant tRNA gene sequences because they "know" those sequences will always be there

cloning an organism is fundamentally a simple process. take a cell. make it "forget" it's an adult cell so it becomes an induced pluripotent stem cell by putting its nucleus into an oocyte (egg cell) that's had its nucleus removed. put it in the uterus of a female of the species (or whatever is appropriate) and wait. important to note that the resulting organism will not be 100% genetically identical to any of its three "parents"

[scar]

There are 2 types of Mutation

Point - meaning 1 point of dna.  can be an addition, deletion (both bugger up the triplet codons for everything downstream of the mutation) or substitution (different levels of effect)

Block - meaning whole chunks of dna are moving.  Inversion - the chunk is put in backwards.  Deletion. Duplication - section from one of a humologous pair is put on its partner.  Translocation - dna from one chromosome will attach to an unrelated chromosome (can sometimes account for down syndrome).

[WhoTookMyUsername]

thanks for the help

another question

- is it possible to have speciation WITHOUT geographic isolation?
E.g. 2 mutations occur both equally beneficial etc... any examples?

Thanks

2) how would the first animals have moved onto land?

Would the first organism to move onto land have had to have simultaneous mutations to prevent it from drying out, as well as to breathe air??

[scar]

- is it possible to have speciation WITHOUT geographic isolation?

I doubt it.  As long as all the mutations and alleles are are swimming in the same gene pool it will be retained by the one species (just be greater variation withing the species).  You really need to isolate the 2 groups somehow to prevent the mixing of traits.  The 'barrier' can come down at a later date but by then they may be diff species...reproduction at different times of year, different mating behaviours, sperm and egg no longer chemically match etc, etc.