Biology Unit 4 Questions Megathread

[WhoTookMyUsername]

Thanks

Aother q)

IN mitosis in organisms with cell walls, does the cell wall "grow" like a cleavage furrow or is it deposited in the middle (I'm think it's the latter)

2) when placing 2 DNA segments into the same plasmids, would you mix the DNA segments first (after cut) and then mix with plasmid to ensure the DNA segments tend  to join the plasmid together ( avoid one gene into one plasmid when you want two into one plasmid )

[HERculina]

^ yea it's more like the second one. A cell plate forms from materials supplied by the golgi vesicles across the midline of the parent cell. And this is where the new cell wall will form. No cleavage furrow

[Russ]

2) when placing 2 DNA segments into the same plasmids, would you mix the DNA segments first (after cut) and then mix with plasmid to ensure the DNA segments tend  to join the plasmid together ( avoid one gene into one plasmid when you want two into one plasmid )

Not sure what you're trying to ask here, but if you want to put 2 DNA segments onto a plasmid you just have to do it with the appropriate restriction enzymes

[Reckoner]

Cheers Hercules, my teacher seemed to use them interchangeably without specifying the differences. Your explanation cleared that up 

[WhoTookMyUsername]

Russ -

Let's say you wish to place GENE A (e.g. GFP gene) and GENE B (amp resistance gene)

you need bacteria which take up the recombinant plasmid to have BOTH genes in the plasmid, not just one.
If you cut gene a, gene B and plasmid and mix first, some plasmids may have  ONLY gene A or gene B, which could invalidate experiment.

So to overcome this, does mixing GENE A and GENE B first before mixing with plasmid ensure a higher portion of plasmids have BOTH genes, not just gene A or gene B ?

[simpak]

By mixing, do you mean you want to join Gene A and Gene B with ligase before inserting them?  That would only work if they were going to be right next to each other...?

[WhoTookMyUsername]

Yeah thats what I mean. Would that give a higher portion of plasmids with both genes thus validating the "selection" process?


How else is it possible to ensure no plasmids have the amp resistance gene alone?

I there a problem if you put the genes together?

[Russ]

You don't need to have them right next to each other, they can be at different sites on the plasmid. I would just add REs for A insertion and REs for B insertion and then screen my plasmids afterwards to ensure they have both (there is no process 100% efficient for transfection).

Given this is bacterial genetics, you probably don't even need to bother making sure that there are 2 genes on the plasmid - just plate onto ampicillin coated media and take any fluorescing colonies, because you know those are the ones you're interested in. Bacteria are cheap and grow quickly, so you can dispose of the ones you don't want.

[Mr. Study]

I probably should've made my questions A LOT smaller. xD

Just this one:

6. For DNA Replication.
    5-prime ------------------------------- 3-prime <--\ My DNA
    3-prime ------------------------------- 5-prime <--/

If that DNA double helix replicates, would it happen like this:

    5-prime--------------------------\
    3-prime-----------------------     \
                                                   \------------3-prime
                                                   /------------5-prime
                                                  /
     3-prime-------------------------/
     5-prime----------------------

[WhoTookMyUsername]

In a cladogram / phylogenic tree does a line coming away from a strait line indicate The new line evolved from the straight line? Or is this an incorrect diagram?

[Kaille]

I don't understand the answer to this question? :S

Mary has a genotype of x^Dx^d for a sex linked recessive disorder (DMD). She marries tim who is a normal male  (x^DY). What is the chance that mary will pass on the DMD allele on to her offspring?

Answer: 1/4- i thought it would be 1/2?

[WhoTookMyUsername]

just do a punnet square. all females unaffected inherit X^D allele. 1/2 Males inherit X^d allele, 1/4 overall are affected

1) In a cladogram / phylogenic tree does a line coming away from a strait line indicate The new line evolved from the straight line? Or is this an incorrect diagram?

2) Does a cline refer to phenotypic variation along an environmental gradiant DUE TO differences in environmental factors influentially the SAME genotype differently or the different selective pressures selecting for DIFFERENT genotypic combinantions ? ( i think its the latter... but definitions in dictionaries are loose).

3) If a species evolves into another species (microevo) , is the ancestor species considered "extinct"?

[Russ]

just do a punnet square. all females unaffected inherit X^D allele. 1/2 Males inherit X^d allele, 1/4 overall are affected

That's not what the question asked though, there is a 50% chance she will produce gametes with the mutant allele. I assume the question is poorly phrased and they intended for it to ask the likelihood of the child being affected?

[WhoTookMyUsername]

yep my mistake, your answer is right or the question is wrong 

(any help for these q's, tend to get lost on previous page XD)
just do a punnet square. all females unaffected inherit X^D allele. 1/2 Males inherit X^d allele, 1/4 overall are affected

1) In a cladogram / phylogenic tree does a line coming away from a strait line indicate The new line evolved from the straight line? Or is this an incorrect diagram?

2) Does a cline refer to phenotypic variation along an environmental gradiant DUE TO differences in environmental factors influentially the SAME genotype differently or the different selective pressures selecting for DIFFERENT genotypic combinantions ? ( i think its the latter... but definitions in dictionaries are loose).

3) If a species evolves into another species (microevo) , is the ancestor species considered "extinct"?

[Kaille]

just do a punnet square. all females unaffected inherit X^D allele. 1/2 Males inherit X^d allele, 1/4 overall are affected

That's not what the question asked though, there is a 50% chance she will produce gametes with the mutant allele. I assume the question is poorly phrased and they intended for it to ask the likelihood of the child being affected?

so based on the question, would 1/2 be correct?