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July 29, 2025, 01:12:12 am

Author Topic: VCE Biology Question Thread  (Read 4940106 times)  Share 

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chemzy

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Re: VCE Biology Question Thread
« Reply #6180 on: September 29, 2015, 03:17:25 pm »
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Thettywetty
Yeah! Like Maca 13 said,

I think because there was a higher mutation rate in mtDNA, that allowed those who lived in Africa to immensely diverge; as higher mutation rate = more variation in the species. Because of great divergence and more variation, it supports the Out-of-Africa hypothesis: that humans diverged and modern humans evolved in other parts of the world.

paper-back

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Re: VCE Biology Question Thread
« Reply #6181 on: September 29, 2015, 04:44:25 pm »
0
Is a second messenger synthesised in the signal transduction pathway of both lipid soluble and insoluble hormones?
Is a G-Protein just a surface membrane receptor?
Can MHC markers be present on pathogens?
« Last Edit: September 29, 2015, 05:00:32 pm by paper-back »

thettywetty

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Re: VCE Biology Question Thread
« Reply #6182 on: September 29, 2015, 04:49:06 pm »
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Mmmm okay I kind of get it now...
Thanks guys!
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Bruzzix

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Re: VCE Biology Question Thread
« Reply #6183 on: September 29, 2015, 05:04:14 pm »
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I need help with a question.

Tay Sachs disease is autosomal recessive. Both a female and a male have a sibling with Tay Sachs but no other family members have the disease. What is the probability of their child having Tay Sachs?
A. 1/4
B. 0
C. 1/9
D. 2/3

I said A because according to my working out, the only parental genotypes from this information could be Aa x Aa, AA x Aa and AA x AA. So the probabilities become 1/4 + 0 + 0 = 1/4. The solution set said C.

Can anyone explain why the answer is C?
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BakedDwarf

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Re: VCE Biology Question Thread
« Reply #6184 on: September 29, 2015, 05:14:33 pm »
+4
I need help with a question.

Tay Sachs disease is autosomal recessive. Both a female and a male have a sibling with Tay Sachs but no other family members have the disease. What is the probability of their child having Tay Sachs?
A. 1/4
B. 0
C. 1/9
D. 2/3

I said A because according to my working out, the only parental genotypes from this information could be Aa x Aa, AA x Aa and AA x AA. So the probabilities become 1/4 + 0 + 0 = 1/4. The solution set said C.

Can anyone explain why the answer is C?

Pr = Pr(mother being Aa|not aa) x Pr(father being Aa|not aa) x Pr(child being aa)
    = 2/3 x 2/3 x 1/4
    = 4/36
    = 1/9
« Last Edit: September 29, 2015, 05:20:32 pm by BakedDwarf »

Bruzzix

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Re: VCE Biology Question Thread
« Reply #6185 on: September 29, 2015, 05:21:24 pm »
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Pr = Pr(mother being Aa|not aa) x Pr(father being Aa|not aa) x Pr(child being aa)
    = 2/3 x 2/3 x 1/4
    = 4/36
    = 1/9
Thank you!
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StupidProdigy

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Re: VCE Biology Question Thread
« Reply #6186 on: September 29, 2015, 08:05:54 pm »
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I'm a bit confused what I'm meant to look for in the attached pic..can someon explain thanks
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sunshine98

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Re: VCE Biology Question Thread
« Reply #6187 on: September 29, 2015, 08:18:31 pm »
+1
I'm a bit confused what I'm meant to look for in the attached pic..can someon explain thanks
Is the answer b? If so , this is how I kinda thought of it .
Receptors are always structures that  another  molecule or structure could attach to, right? So wouldn't  that mean that all those structures on the cell with open ends  , that is , all those structures that another thing could bind to ,  are receptors? This  rules out A , C  and D.
Interesting q ,tho

BakedDwarf

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Re: VCE Biology Question Thread
« Reply #6188 on: September 29, 2015, 08:19:29 pm »
+1
I'm a bit confused what I'm meant to look for in the attached pic..can someon explain thanks

I got B. I'll provide an explanation if it's right

StupidProdigy

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Re: VCE Biology Question Thread
« Reply #6189 on: September 29, 2015, 08:23:14 pm »
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Yeah it's B guys, thanks
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Gromekk

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Re: VCE Biology Question Thread
« Reply #6190 on: September 29, 2015, 08:41:15 pm »
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Hey all,

I've just got a question about the vcaa 2014 exam, i correctly identified the mode of inheritance as autosomal recessive, and i wrote down my reasons as
  • the trait skips a generation
  • not all the males of the female with the trait show the trait

Would these be sufficient for full marks?

Thanks heaps

jyodesh.com

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Re: VCE Biology Question Thread
« Reply #6191 on: September 29, 2015, 10:24:36 pm »
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What uses electrons in the light dep dent stage of photosynthesis?

A. The conversion of ADP+Pi into ATP
B. The conversion of NADP+ into NADPH

Aren't they both correct?

ATP is an energy carrying molecule, this energy comes from the energy stored in the bonds between phosphate groups.
NADPH is an electron carrying molecule. It carries high energy electrons and this energy can be used to convert ADP to ATP.
(If you do chemistry) NADPH is a reductant and can lose two electrons in an oxidation reaction to form NADP+.
NADPH --> NADP+ + H+ + 2e-
And vice versa in the context of your question
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Sine

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Re: VCE Biology Question Thread
« Reply #6192 on: September 29, 2015, 10:40:38 pm »
+4
What are the specifics we need to know about Human Intervention in Evolution and to what extent?

@Cosine
For VCE Biology purposes we say that immune cells recognise self-cells as per self-antigens which are the MHC I markers and thus does not respond.
For example in VCE an autoimmune disease is when the immune system recognises self-cells as foreign and thus produces a response.

Hey all,

I've just got a question about the vcaa 2014 exam, i correctly identified the mode of inheritance as autosomal recessive, and i wrote down my reasons as
  • the trait skips a generation
  • not all the males of the female with the trait show the trait

Would these be sufficient for full marks?

Thanks heaps
No you wouldn't get you'd get those marks all pedigree questions you need to specify the individuals and the circumstances.
Don't say skips a generation, say it wasn't found in the parents (specify two parents as per their generation and number) who don't have the trait produces a child(specify child) which does have the trait.

I didn't look at the question specifically because I want to do it in proper exam conditions before the exam to get an idea of what study score I would get. XD
« Last Edit: September 29, 2015, 10:46:43 pm by Sine »

jyodesh.com

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Re: VCE Biology Question Thread
« Reply #6193 on: September 30, 2015, 12:45:33 am »
+3
Cheers man, but does NADPH also carry electrons as well as hydrogen atoms?
I thought that it was electrons that actually supplied the energy. If the bonds in ATP are broken, then where does this energy from the 'bond' come from? Is it like heat energy or?

Yeah NADPH carries 2 electrons and one hydrogen atom (this is referring to exchangeable electrons and hydrogens). Electron carriers such as NADPH, NADH and FADH2 do carry high energy electrons (think of these molecules as strong reductants, strong reductants can provide higher voltages in a galvanic cell because they hold electrons with higher potential energy) but this energy can't be accessed in a lot of biochemical reaction pathways for example the synthesis of glycogen requires phosphorylation using ATP, it pairs an endergonic reaction (polymerisation) with a highly exergonic reaction (ATP --> ADP), overall this makes the reaction favourable and allows it to occur. This reaction can't be achieved using an electron carrier because well chemistry.

The high energy bonds in ATP are a form of chemical potential energy which is used to create different forms of chemical potential energy (e.g. synthesis of carbohydrates/proteins/DNA/lipids) as well as maintaining intracellular and extracellular environments (e.g. Na+/K+ ATPase antiporter (maintains electrochemical potential energy)). Of course energy conversions are almost never 100% and a lot of energy is released as heat during these processes.

So where does this energy come from? Well in the beginning there was a big bang... etc etc light energy from the sun etc photosynthesis etc im not a plant guy etc etc glucose. ATP can be formed in two ways, through enzymatic cleavage of a high energy phosphate bond or through oxidative phosphorylation by ATP synthase. The catabolism of glucose begins with glycolysis, this pathway produces ATP enzymatically through a series of reactions involving the breakage of carbon-carbon bonds which creates reactive functional groups (specifically aldehyde groups) which presents a great source of chemical potential energy. This is used to enzymatically add inorganic phosphate which is followed by removal of the phosphate group using ADP to produce ATP. During this pathway the glycolytic intermediates also get oxidised, causing the reduction of NAD+ to NADH. At the end of glycolysis you get pyruvate which is oxidatively decarboxylated (oxidation reaction that releases a CO2 molecule) to acetyl CoA which then enters Krebs cycle. The catabolism of different biomolecules provide energy in their own pathway but they all converge at acetyl-CoA which can enter Kreb's cycle.

Kreb cycle intermediates are oxidatively decorboxylated to produce electron carriers NADH and FADH2 and CO2. These electron carriers can then donate their electrons (oxidation) to the electron transport chain which involves a series of redox reactions terminating at the reduction of oxygen, and just like in galvanic cells, the energy released during these redox reactions is harnessed a sort of electrical current which induces changes in the confromation of inner mitochondrial membrane (IMM) proteins and the pumping of hydrogen ion across the IMM. This sets up an electrochemical gradient. Hydrogen ions want to move back into the mitochondrial matrix because it will be traveling down its electrical and concentration gradients: from a region of high concentration and high positive charge to a region of low concentration and low positive charge. This electrochemical potential energy is harnessed by ATP synthase to create chemical potential energy in the bonds of ATP.

So overall, the aerobic respiration of glucose involves the breakage of carbon-carbon bonds and the oxidation of carbon molecules which is utilised by the body for energy. Aerobic respiration is like the combustion of glucose but carried out over a convoluted series of controlled steps allowing the controlled the release of energy.

Thats probably more detail than you need or asked for but I hope it helps you understand whats going on better.
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cosine

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Re: VCE Biology Question Thread
« Reply #6194 on: September 30, 2015, 08:46:04 am »
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Do DNA primers or RNA primers bind to the 3' end of a DNA strand to initiate PCR (DNA polymerase to progress along the strands). I remember someone said it was actually RNA primers that bind to the DNA strand, but on wikipedia it says that DNA primers bind?

"DNA. Primers (short DNA fragments) containing sequences complementary to the target region along with a DNA polymerase, which the method is named after, are key components to enable selective and repeated amplification"

Edit: After some research:

- During DNA replication RNA primers are synthesised by DNA primase (also known as RNA polymerase because it is synthesising RNA nucleotides)
- This also clicks in because It was actually said that RNA polymerase does not need primers, it can automatically synthesise in the 5-3 direction without the addition of primers, which also explains how RNA polymerase (DNA Primase) can add the RNA primers to the DNA parent strands.

However, I still do not get why during PCR, DNA primers are added and not RNA primers?
« Last Edit: September 30, 2015, 09:39:46 am by cosine »
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