VCE Biology Question Thread

[usernameincorrect]

You have two chromosomes we are dealing (1 and 2)  with: BOTH REPLICATE so visually it looks like
                                                                                    XX ( chromosome 1) and XX ( chromosome 2)
Now the two sister chromatids will cross over which results in recombinant DNA!
So for chromosome 1: The chromatids have a different combination of alleles now!
2 are normal whilst 2 are recombined
Now the same thing happens with chromosome 2
2 are normal whilst 2 are recombined
So we want the chance a sperm cell has both a normal 2 and a normal 1 chromosome
There is 0.5 chance of getting a normal 1 chromosome and 0.5 chance of getting a normla 2 chromosome
HENCE 0.5 X 0.5 = 0.25
AKA 1/4

idk if that is correct but that is how i would figure it out

Thanks for replying If that happens, the way I'm looking at it, there will be four gamates, 2 will have the recombinant chromosome 1 and 2, and two gamates will have the normal 1 and 2. I must be misunderstanding something here 

[The Usual Student]

Thanks for replying If that happens, the way I'm looking at it, there will be four gamates, 2 will have the recombinant chromosome 1 and 2, and two gamates will have the normal 1 and 2. I must be misunderstanding something here 

Best way to think about it
Lets say R1 = recombinant chromosome 1
N1 = Normla chromosome 1
same thing for chromosome 2 = N2 and R2

As per the rule of independent assortment the Chromosome 1 is split into 2 R1s and 2 N1s vice versa for chromosome 2
we have in total N1 N1 N2 N2 R1 R1 R2 R2
so if one chromsome has
N1 and N2

that means we have  R1 R1 R2 R2 N1 N2
Left to be distributed:
It could be R1 N2
or N1 R2
or R1 R2
or N1 N2
ect

Point is the recombinant DNA does not need to stick with the recombinant DNA! hopefully that clears everything up if not I can elaborate

[homosapien]

Does only the template strand of DNA contain genes?
I thought it was the two strands together with complementary bases forming the gene

[Springyboy]

Does only the template strand of DNA contain genes?
I thought it was the two strands together with complementary bases forming the gene

Yep, the template strand is unwound to form pre-mRNA, which after splicing and capping forms mRNA which creates the genes.

However, the complementary bases that are formed from DNA creates the mRNA via transcription, which after translation forms your amino acids and your polypeptide chain.

Genes aren't just found in DNA, but also in mRNA, so ensure that if you are asked a definition of genes, you say that it's a group of bases (DNA or mRNA) that codes for a specific trait. It's not just DNA where it's found but also in mRNA, where amino acids are created from.

Hope I cleared that one up for you.

[eroos]

 could someone please explain to me question 8cii in the 2015 vcaa exam? thank you

[homosapien]

Would you say 'DNA is transcribed' or 'mRNA is transcribed'
also if DNA is transcribed, the product (mRNA is made in 5' to 3' direction but what direction would you say DNA is transcribed?

[Springyboy]

Would you say 'DNA is transcribed' or 'mRNA is transcribed'
also if DNA is transcribed, the product (mRNA is made in 5' to 3' direction but what direction would you say DNA is transcribed?

Always DNA is transcribed, mRNA is translated. Since DNA is anti-parallel, then as the new strand is synthesised in the 5' to 3' direction, then the template strand (old strand) is synthesised using RNA polymerase from the 3' to 5' direction to form the new strand.

Try not to get that confused as there's always tricks on the exams as to whether or not it's the old or new strand.

[Angelx001]

Hi, do both protein based & steroid based hormones cause transcription & translation to occur within the cell?

[The Usual Student]

Hi, do both protein based & steroid based hormones cause transcription & translation to occur within the cell?

Not entirely sure but I think they both can but steroid based hormones tend to be the ones who actually cause transcription and translation to occur.

[vox nihili]

Hi, do both protein based & steroid based hormones cause transcription & translation to occur within the cell?

Both do.


For steroids this is really how they do most of what they do, whereas for peptide hormones they can also activate enzymes etc.

[geminii]

Thanks to vox nihili for answering my previous question about reverse transcriptase!

I have another question - are translocation and crossing over the same thing or not? And if not, what overall topic are they a part of and what are they?

Thank you guys so so so much!

EDIT:

Both do.


For steroids this is really how they do most of what they do, whereas for peptide hormones they can also activate enzymes etc.

I know I'm not the person who asked this, but could you elaborate on this please? How do hormones cause transcription and translation? Do you mean as a result of the hormone binding to the receptor on/in a cell leading to signal transduction where gene expression is altered?

[hodang]

Can anyone confirm:

1) facilitard diffusion transports glucose molecules across the membrane with the aid of protein channels? And not carrier proteins? Carrier proteins invoked in AT only?

2) lysosomes lyse bacterial membranes and not cell walls? (Read this someone not sure if true)

3)  Do we say signalling molecule binds to receptors on the post synaptic membrane or terminal? Which is a better term to use? "Membrane or terminal?"

4) Do cytotoxic T cells secrete chemicals or proteins? So many processes occur with the Tc cells, what is the order they occur in? Do they recognise antigenic fragment on their MHC class 1 markers, and then leave be lymph nodes where they release cytokines that promote inflammation, allow phagocytes to engulf parhogen and destroy the pathogen (infected cells/cancer cells) ? Are cytokines the proteins that cytotoxic T cells produce that lyse bacterial membranes?

5) are amino acid sequences same as DNA hybridisation?

[homosapien]

as exons are coding regions could they be considered as genes?

[vox nihili]

Thanks to vox nihili for answering my previous question about reverse transcriptase!

I have another question - are translocation and crossing over the same thing or not? And if not, what overall topic are they a part of and what are they?

Thank you guys so so so much!

EDIT:

I know I'm not the person who asked this, but could you elaborate on this please? How do hormones cause transcription and translation? Do you mean as a result of the hormone binding to the receptor on/in a cell leading to signal transduction where gene expression is altered?

Translocation/crossing-over: different processes. Translocation is where you get bits of chromosome going where they shouldn't be (so they get jumbled up), whereas crossing over is where homologous chromosomes swap the same bits.



It depends on the type of hormone. You don't need to know the details, but the way you described it is certainly correct for protein hormones. Some of the proteins activated in signal transduction are able to bind DNA and bring RNA polymerase to it, thereby transcribing those genes (they could also block transcription as well!).
In the case of steroid hormones, it's actually the steroid hormone receptor itself that binds to DNA and can either block or encourage transcription.

Can anyone confirm:

1) facilitard diffusion transports glucose molecules across the membrane with the aid of protein channels? And not carrier proteins? Carrier proteins invoked in AT only?

2) lysosomes lyse bacterial membranes and not cell walls? (Read this someone not sure if true)

3)  Do we say signalling molecule binds to receptors on the post synaptic membrane or terminal? Which is a better term to use? "Membrane or terminal?"

4) Do cytotoxic T cells secrete chemicals or proteins? So many processes occur with the Tc cells, what is the order they occur in? Do they recognise antigenic fragment on their MHC class 1 markers, and then leave be lymph nodes where they release cytokines that promote inflammation, allow phagocytes to engulf parhogen and destroy the pathogen (infected cells/cancer cells) ? Are cytokines the proteins that cytotoxic T cells produce that lyse bacterial membranes?

5) are amino acid sequences same as DNA hybridisation?

1. Carrier proteins are involved in both facilitated diffusion and active transport. Channel proteins are only involved in facilitated diffusion.

2. Untrue

3. Post-synaptic membrane...terminal means the end, the dendrites are quite the opposite; they're the start! Neurotransmitters are released from axon terminals

4. Proteins are chemicals. Not sure what you mean by your second question. Cytotoxic T-cells leave the lymph node and recognise the antigen in the tissues; this is how they know what cells to kill—they don't have antigen presented to them in the lymph node like helper T-cells. Cytokines are signalling molecules that cells of the immune system use to communicate with each other; the proteins that are used to lyse cells are called granzymes and perforins.

5. No

as exons are coding regions could they be considered as genes?

No. A gene includes the introns as well.

[The Usual Student]

can someone tell me what we really need to know about the blood antigen system :p
My teacher said it really wasn't important