VCE Biology Question Thread

[vox nihili]

Few questions about meiosis:

1. To produce sperm cells or egg cells, they are produced from a cell that is a diploid cell. I know this diploid cell is a germ cell, but is it a somatic cell?

2. When you define diploid cells, would you say that only body cells are diploid?

3. When does DNA replication occur during meiosis? Is it in meiosis 1 or 2?

4. Are there X and Y or X and X chromosomes in ALL of our cells? Somatic AND gametes?

5. How much do we need to know about crossing over?

6. Is there DNA replication during Meiosis 2?

7. When the gametes are produced, they only have 23 chromosomes, right? If so, what happens to the sperm/egg cells now?

1. No, it's not a somatic cell.

2. Diploid cells are defined as cells with two sets of chromosomes. You shouldn't define them on the basis of what kind of cells are diploid and what kind of cells are haploid.

3. Neither. DNA replication occurs during the S phase of the cell cycle, which precedes the G2 phase and the M (mitosis/meiosis) phase.

4. Yes

5. You need to know when it happens and what it entails. You also need to have an understanding of what the outcomes of crossing-over might be.

6. Again, DNA replication does not occur during meiosis at all.

7. They do. They sit around and wait to be ejaculated or fertilised.

[cosine]

1. No, it's not a somatic cell.

2. Diploid cells are defined as cells with two sets of chromosomes. You shouldn't define them on the basis of what kind of cells are diploid and what kind of cells are haploid.

3. Neither. DNA replication occurs during the S phase of the cell cycle, which precedes the G2 phase and the M (mitosis/meiosis) phase.

4. Yes

5. You need to know when it happens and what it entails. You also need to have an understanding of what the outcomes of crossing-over might be.

6. Again, DNA replication does not occur during meiosis at all.

7. They do. They sit around and wait to be ejaculated or fertilised.

Cheers Mr. T-Rav.

So diploid cells contain 2n number of chromosomes. Does that mean all somatic cells are diploid cells, but not all diploid cells are somatic cells?

Also during anaphase I of meiosis I, the homologous chromosomes exist as sister chromatids. So during this phase the the chromosomes are pulled at opposite poles of the cell, are the sister chromatids separated, or are the homologous chromosomes separated? Which one is it, and why?

Thank you

[vox nihili]

Cheers Mr. T-Rav.

So diploid cells contain 2n number of chromosomes. Does that mean all somatic cells are diploid cells, but not all diploid cells are somatic cells?

Also during anaphase I of meiosis I, the homologous chromosomes exist as sister chromatids. So during this phase the the chromosomes are pulled at opposite poles of the cell, are the sister chromatids separated, or are the homologous chromosomes separated? Which one is it, and why?

Thank you

Yes, essentially. There are some organisms though where somatic cells are haploid and so on, so it's better to describe these terms with respect to the number of chromosomes—which is actually what they're describing.

Homologous chromosomes are separated. You don't need to know why that's the case. Personally, I actually don't know why other than that's just the order evolution has set up. There could be an advantage to doing it that way, maybe not. No idea to be honest.

[StupidProdigy]

With plasmid recombination, what actually happens after the gene is inserted and after the colony replicates. Like I've watched videos that explain up until this point but I don't actually understand what happens next because the videos stop here...are bacteria samples with the recombinant plasmid able to be inserted into an organism or something? Thankya

[cosine]

With plasmid recombination, what actually happens after the gene is inserted and after the colony replicates. Like I've watched videos that explain up until this point but I don't actually understand what happens next because the videos stop here...are bacteria samples with the recombinant plasmid able to be inserted into an organism or something? Thankya

These bacterial cells that contain the recombinant plasmids are known as transformed bacteria. These bacteria now contain the gene of interest, say for example we inserted the gene for human insulin production into the plasmid, and this plasmid was taken up by the bacteria. The transformed bacteria now has the genetic instructions to produce human insluin, but it's only 1 bacterial cell, how much insulin can that produce so that economical yield can be profitable? Not much... So it is vital to kill off the non-transformed bacteria, and so only the transformed ones remain in the sample and contain the genes for inulin. These bacterial cells are treated with their nutrients they require to survive, reproduce asexually and after some time, there will literally be millions of the bacterial cells that contain the required gene for insulin. Now the gene can be switched on by inserting a certain sugar (or other molecule) that will trigger the production of the human insulin (remember, genes can be switched on and off). This insulin is now produced by millions of bacterial cells, and the insulin can be obtained, purified of other chemicals, and injected into diabetics... yay!

Hope that helped

[cosine]

I would appreciate it if someone could answer these questions I have piled up:

1. Are germ line cells sex cells that have 2n number of chromosomes?
2. If the above is true, are germ line cells gametes? Or are only sperm and egg cells gametes?
3. Would you say that meiosis is the nuclear division of germ line cells into four varying (genetically) daughter cells? Or would just saying division of sex cells suffice?

Thank you!

[cosine]

Do we need to actually know about G1, G0, G2 and S phases? If we do are these appropriate (just incase it's on my sac):

G1 phase: The cell grows and this takes approximately 8-10 hours
G0 phase: If the cell has not fully grown or has been damaged, it will repair and then undergo G1 phase again
S phase: The DNA of the cell is replicated and this takes approximately 6-8 hours
G2 phase: The cell prepares for mitosis and most of the organelles are produced and this takes 4-6 hours
M phase: Mitosis takes place.

Also, do we need to know about the check points between G1 and S phases, the check point between G2 and S phase, and the check point between Metaphase and Anaphase?

Also also is cytokinesis part of mitosis? Why/why not?

Many thanks

[heids]

I would appreciate it if someone could answer these questions I have piled up:

1. Are germ line cells sex cells that have 2n number of chromosomes?
2. If the above is true, are germ line cells gametes? Or are only sperm and egg cells gametes?
3. Would you say that meiosis is the nuclear division of germ line cells into four varying (genetically) daughter cells? Or would just saying division of sex cells suffice?

Thank you!

Dunno actually, I always thought of germline cells as both the 'parent cells' in meiosis (i.e. the original diploid ones) and the 'daughter cells', the final gametes (the haploid egg/sperm).  I can't see how it could be both, I'd just never thought about it before   So google it (as I've said maannnnyyyy times before, googling stuff is your best bet; e.g. you asked a question about what splicing was earlier, when you could have just typed 'define splicing' into Google which would perfectly get your answer, even faster than it takes to type the question here)

Yeah, I'd go with: meiosis is the nuclear division of germline cells into four genetically varying haploid daughter cells.  Probably not the best, but good enough.

Do we need to actually know about G1, G0, G2 and S phases?  YES If we do are these appropriate (just incase it's on my sac):

G1 phase: The cell grows and this takes approximately 8-10 hours the time will vary between different organisms/cells/situations, definitely don't learn it.  The cell grows, duplicates organelles, and produces proteins/ATP etc. needed for the S phase
G0 phase: If the cell has not fully grown or has been damaged, it will repair and then undergo G1 phase again yeah, but this can also just be a 'resting phase' not necessarily because of damage, just because for whatever reason the cell doesn't yet need to reproduce
S phase: The DNA of the cell is replicated and this takes approximately 6-8 hours
G2 phase: The cell prepares for mitosis and most of the organelles are produced and this takes 4-6 hours ATP/proteins/other preparations needed for mitosis
M phase: Mitosis takes place.

Also, do we need to know about the check points between G1 and S phases, the check point between G2 and S phase, and the check point between Metaphase and Anaphase? I simply learnt that checkpoints exist during the G1 and G2 phases, to make sure nothing goes wrong.

Also also is cytokinesis part of mitosis? Why/why not? As I said last time I answered your question: cytokinesis is the division of the cytoplasm, while mitosis is the division of the nucleus.  They happen at the same time (cytokinesis happens with telophase) but cytokinesis is not part of mitosis.

Many thanks

[cosine]

Dunno actually, I always thought of germline cells as both the 'parent cells' in meiosis (i.e. the original diploid ones) and the 'daughter cells', the final gametes (the haploid egg/sperm).  I can't see how it could be both, I'd just never thought about it before   So google it (as I've said maannnnyyyy times before, googling stuff is your best bet; e.g. you asked a question about what splicing was earlier, when you could have just typed 'define splicing' into Google which would perfectly get your answer, even faster than it takes to type the question here)

Yeah, I'd go with: meiosis is the nuclear division of germline cells into four genetically varying haploid daughter cells.  Probably not the best, but good enough.

So organelles are produced in both G1 and G2 phase?

Thank you so much bangali_lok!
Do you know when we, normal users of AN, can PM again?? xD

oh and i need you for english tutoring but how can I contact?

[heids]

So organelles are produced in both G1 and G2 phase?

I don't actually know.  I should stop answering questions until I have microbio/immunology/genetics majors behind me...

Do you know when we, normal users of AN, can PM again?? xD

Dunno what I'm allowed to say (don't know much anyway), but I think the site will go on another holiday after the UMAT and come back hopefully all fixed.  P.S. don't stress about my PM, sorry I sent it.

oh and i need you for english tutoring but how can I contact?

Email (should be a little button on my profile, I changed to letting people email me because PMs were down).

[cosine]

I don't actually know.  I should stop answering questions until I have microbio/immunology/genetics majors behind me...
Dunno what I'm allowed to say (don't know much anyway), but I think the site will go on another holiday after the UMAT and come back hopefully all fixed.  P.S. don't stress about my PM, sorry I sent it.
Email (should be a little button on my profile, I changed to letting people email me because PMs were down).

I emailed

Sorry about the questions guys

1. Do we need to know how the cell plate is formed during plant cytokinesis? (mitosis)

2. Bacterial cells, plants cells and unicellular cells do not undergo meiosis right? Because they produce asexually, right?

3. How much do we need to know about bacterial division, binary fission?

Thank you xD

[grannysmith]

I emailed

Sorry about the questions guys

1. Do we need to know how the cell plate is formed during plant cytokinesis? (mitosis)

2. Bacterial cells, plants cells and unicellular cells do not undergo meiosis right? Because they produce asexually, right?

3. How much do we need to know about bacterial division, binary fission?

Thank you xD

1. Nah
2. Sexually reproducing plants definitely undergo meiosis, think pollen/stamen/carpels and all that boring unit 1/2 stuff
3. You need to know the differences between fission and mitosis, which inherently lies in the structure of the respective organisms

[BakedDwarf]

In gel electrophoresis, do DNA fragments move in the gel because they have an overall negative charge due to their phosphate groups. That is, because the agarose gel has two different charged poles, one positive and one negative, when the DNA fragments are placed at the negative end, they move towards the positive one when an electric current is run through a gel. Is this right?

[heids]

In gel electrophoresis, do DNA fragments move in the gel because they have an overall negative charge due to their phosphate groups. That is, because the agarose gel has two different charged poles, one positive and one negative, when the DNA fragments are placed at the negative end, they move towards the positive one when an electric current is run through a gel. Is this right?

Yes.

[cosine]

Thanks grannysmith!

1. Would we lose marks if we called chromatin chromosomes? For example, the S phase's DNA structure is chromatin, but if I say that during the S phase each chromosome is replicated to produce sister chromatids, would this be incorrect?

2. Is there a checkpoint between the S phase and G2 phase?

3. Describe a difference between meiosis and mitosis: Mitosis results in two identical diploid daughter cells, whereas meiosis results in four genetically varying haploid daughter cells. Is this correct guys?

Many thanks