HSC Biology Question Thread

[liya1234]

Can someone please help me with this question and also explain it... there are no marking guidelines for 2007 hsc bio so I don't know if I'm doing it right.

So for part a) I would talk about:
- independent assortment: the chromosomes have randomly lined up in the centre with their homologous pair
- crossing over: the inner chromatids of the AB and ab chromosomes have crossed over to form new allele combinations

For part b), the allele combinations would be 1. ABDE  2.AbDE  3.aBde  4. abde
To figure this out, I just imagine the four gametes that would be produced. In this case they have shown the two sets of chromosomes moving to opposite sides of the cell to form two cells for the next phase, so we know that in prophase II one cell has the AB/Ab and DE/DE chromosomes while the other cell has the aB/ab  and de/de chromosomes.
- In that first cell (AB/Ab and DE/DE) the chromosomes will again line up randomly and go through the process to produce two more cells. Each of these two cells should have one allele of each of the genes so if you just imagine them separating into the chromatids you can see one cell will have an ABDE combination and the other will have an AbDE combination of alleles.
- repeat this with the other cell with prophase II (aB/ab and de/de) and the combinations produced would be aBde and abde
Thus, the four combinations produced would be ABDE, AbDE, abde, abde

Hope that was helpful and sorry if that explanation was kinda complicated lol! Please feel free to clarify anything

[angelahchan]

So for part a) I would talk about:
- independent assortment: the chromosomes have randomly lined up in the centre with their homologous pair
- crossing over: the inner chromatids of the AB and ab chromosomes have crossed over to form new allele combinations

For part b), the allele combinations would be 1. ABDE  2.AbDE  3.aBde  4. abde
To figure this out, I just imagine the four gametes that would be produced. In this case they have shown the two sets of chromosomes moving to opposite sides of the cell to form two cells for the next phase, so we know that in prophase II one cell has the AB/Ab and DE/DE chromosomes while the other cell has the aB/ab  and de/de chromosomes.
- In that first cell (AB/Ab and DE/DE) the chromosomes will again line up randomly and go through the process to produce two more cells. Each of these two cells should have one allele of each of the genes so if you just imagine them separating into the chromatids you can see one cell will have an ABDE combination and the other will have an AbDE combination of alleles.
- repeat this with the other cell with prophase II (aB/ab and de/de) and the combinations produced would be aBde and abde
Thus, the four combinations produced would be ABDE, AbDE, abde, abde

Hope that was helpful and sorry if that explanation was kinda complicated lol! Please feel free to clarify anything

So for part a) I would talk about:
- independent assortment: the chromosomes have randomly lined up in the centre with their homologous pair
- crossing over: the inner chromatids of the AB and ab chromosomes have crossed over to form new allele combinations

For part b), the allele combinations would be 1. ABDE  2.AbDE  3.aBde  4. abde
To figure this out, I just imagine the four gametes that would be produced. In this case they have shown the two sets of chromosomes moving to opposite sides of the cell to form two cells for the next phase, so we know that in prophase II one cell has the AB/Ab and DE/DE chromosomes while the other cell has the aB/ab  and de/de chromosomes.
- In that first cell (AB/Ab and DE/DE) the chromosomes will again line up randomly and go through the process to produce two more cells. Each of these two cells should have one allele of each of the genes so if you just imagine them separating into the chromatids you can see one cell will have an ABDE combination and the other will have an AbDE combination of alleles.
- repeat this with the other cell with prophase II (aB/ab and de/de) and the combinations produced would be aBde and abde
Thus, the four combinations produced would be ABDE, AbDE, abde, abde

Hope that was helpful and sorry if that explanation was kinda complicated lol! Please feel free to clarify anything

Your method of doing part b makes heaps of sense, but I'm confused about the answers on the success one HSC Bio book
it says that for part b) answers are AE, BD, bD, ae, Bd, bd
I'm confused because why would alleles for non homologous chromosomes (idk what you call them) mix together?

[kdurante]

So for part a) I would talk about:
- independent assortment: the chromosomes have randomly lined up in the centre with their homologous pair
- crossing over: the inner chromatids of the AB and ab chromosomes have crossed over to form new allele combinations

For part b), the allele combinations would be 1. ABDE  2.AbDE  3.aBde  4. abde
To figure this out, I just imagine the four gametes that would be produced. In this case they have shown the two sets of chromosomes moving to opposite sides of the cell to form two cells for the next phase, so we know that in prophase II one cell has the AB/Ab and DE/DE chromosomes while the other cell has the aB/ab  and de/de chromosomes.
- In that first cell (AB/Ab and DE/DE) the chromosomes will again line up randomly and go through the process to produce two more cells. Each of these two cells should have one allele of each of the genes so if you just imagine them separating into the chromatids you can see one cell will have an ABDE combination and the other will have an AbDE combination of alleles.
- repeat this with the other cell with prophase II (aB/ab and de/de) and the combinations produced would be aBde and abde
Thus, the four combinations produced would be ABDE, AbDE, abde, abde

Hope that was helpful and sorry if that explanation was kinda complicated lol! Please feel free to clarify anything

Thankyou so much for the help !!

[liya1234]

Your method of doing part b makes heaps of sense, but I'm confused about the answers on the success one HSC Bio book
it says that for part b) answers are AE, BD, bD, ae, Bd, bd
I'm confused because why would alleles for non homologous chromosomes (idk what you call them) mix together?

Oh that's so weird I can't see how that would be the answer either?? Maybe I'm missing something but I think it may just be that the answer in the book is wrong bc my chem tutor has told me that the success one book for chemistry, though very helpful, is not always entirely accurate as it is written independently by teachers not nesa so i'm guessing it's the same with the bio one?  I'm not sure, sorry - maybe someone else can shed some light onto this?

[pikachu975]

Hey, how do I stop writing excessivley long answers for the core component of the exam?
I just practiced a 5 marker for blueprint of life and spent almost a page answering it, we wont get that much space in the exam though so how do I make it more concise?

Ask for an extra writing booklet

[adelaidecruz]

Hi everyone -- not sure if this has been asked before but does anyone know of a good example for a transgenic animal? Info on oncomouse seems a bit limited..

[sidzeman]

Hey could someone help me out with these 2 questions from the 2012 HSC
Membrane bound organelles means it cannot be a virus or prion, but I''m not sure where to go from there.

For q19, I thought opening stomota's would result in the plant become less cool, as its the site of water loss. Is it meant to be because it inititates the transpiration pull of water up the plant, thus cooling it maybe?

[adelaidecruz]

For q19, I thought opening stomota's would result in the plant become less cool, as its the site of water loss. Is it meant to be because it inititates the transpiration pull of water up the plant, thus cooling it maybe?

Opening of the plant's stomata would allow water inside of the plant to evaporate (evaporative cooling), reducing the internal temperature of the plant. And yes you're right, it also initiates transpiration pull as it creates tension at the top of the water column in the xylem. It's also worth it to note that the plant runs the risk of dehydration during this process.

[caitlinlddouglas]

Hey could someone help me out with these 2 questions from the 2012 HSC
Membrane bound organelles means it cannot be a virus or prion, but I''m not sure where to go from there.

For q19, I thought opening stomota's would result in the plant become less cool, as its the site of water loss. Is it meant to be because it inititates the transpiration pull of water up the plant, thus cooling it maybe?

Hey! For the first question bacteria are procariotic cells so by elimination it's a protozoan.
For the second one I think the plant opens its stomata to lose some water through transpiration as this process helps to remove heat energy, thus cooling the plant. When the temperature gets really hot I'm pretty sure some plants close their stomata so they don't lose too much water .

[caitlinlddouglas]

Hi everyone -- not sure if this has been asked before but does anyone know of a good example for a transgenic animal? Info on oncomouse seems a bit limited..

I think there are a type of salmon by I can't remember the name! Do we need to know an animal?

[Natasha.97]

Hi everyone -- not sure if this has been asked before but does anyone know of a good example for a transgenic animal? Info on oncomouse seems a bit limited..

Hi!

bGH (Bovine Growth Hormone) is inserted into salmon, which results in larger + faster growing fish

[adelaidecruz]

Hi!

bGH (Bovine Growth Hormone) is inserted into salmon, which results in larger + faster growing fish

Awesome, thanks!

[sidzeman]

Thank you so much!
Also, could someone help me with what I would discuss for this 8 marker (Genetics elective)
(d) Compare and contrast the effects of germ line mutation and transposable genetic 8 elements on whole organisms.

[bridie_2345]

Hey this is the method i have for how to produce a transgenic species and i just wanted to make sure it was correct or if it had too much/too little detail? Thanks!
1. Identify desired gene
2.Isolate genes using restriction enzymes that cuts out sections of DNA from both organisms (often bacteria) so sticky ends of DNA match, creating recombinant DNA when inserted into the genome of the second organism (the plasmid of the bacteria)
3. Make multiple copies of the gene
4. Insert gene into the organism/culture and infect a tissue with it.

[ca052267]

can someone help me with this question?
It's from 2015 HSC paper - q15

I thought the answer was A, but apparently it's C.

Someone please explain...