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Thread: HSC Biology Marathon 2015

  1. #51
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    Re: HSC Biology Marathon 2015

    Indeterminate.
    To be honest it's difficult to explain it but you figure it out by assuming that the trait is recessive and then assigning the recessive alleles to each affected member. You then use "trial and error" to see if it's correct. Assuming it's recessive, then the mum is (XtXt) and the dad is (XTY), then the possible combinations for their offspring are (using phenotypes) are 2 carrier females: 2 affected males, but their sons aren't affected. If you assume it's dominant and trial and error the different combinations, you'll also get the same result.

    Hope this helps

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    Re: HSC Biology Marathon 2015

    Quote Originally Posted by astab View Post
    Indeterminate.
    To be honest it's difficult to explain it but you figure it out by assuming that the trait is recessive and then assigning the recessive alleles to each affected member. You then use "trial and error" to see if it's correct. Assuming it's recessive, then the mum is (XtXt) and the dad is (XTY), then the possible combinations for their offspring are (using phenotypes) are 2 carrier females: 2 affected males, but their sons aren't affected. If you assume it's dominant and trial and error the different combinations, you'll also get the same result.

    Hope this helps
    A more simplified answer would be that the trait is recessive because it does not appear in all generations, if it did it would have been dominant. This is a really easy way for figuring out questions like these.

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    Re: HSC Biology Marathon 2015

    Is that what your answers say? I'm not entirely convinced that it's recessive.

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    Re: HSC Biology Marathon 2015

    Quote Originally Posted by astab View Post
    Is that what your answers say? I'm not entirely convinced that it's recessive.
    Well it's not a question taken out of the book, I just looked up a pedigree that had a recessive trait and I found the above pedigree. Well I say it's recessive because like what I said it does not appear in all generations.

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    Re: HSC Biology Marathon 2015

    Isn't it recessive as girl has it but parents don't have it?

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    Re: HSC Biology Marathon 2015

    Quote Originally Posted by DepressedPenguino View Post
    A pulse oximeter is an instrument that can be used to measure the oxygen saturation levels in the blood. It can be clipped onto a finger and, by passing a beam of infrared light through the finger, the amount of infrared light absorbed can be used to measure the saturation level of harmoglobin and thus the oxygen saturation level. The oxygen saturation level is delivered as a percentage.
    You could also use a arterial blood gas analysis which is essentially a invasive technology that involves taking a same of the patients blood and then analysing the pH of the blood through a blood gas analyser to determine the carbon dioxide levels. This technology if the physician suspects that the patient has lung disease, kidney disease, metabolic disease or injuries that affect breathing.

    If you want a more modern technology a unisense micro optode and oxygen microsensor could work.
    Unisense micro-optode utilises optical fibres that quenchers the luminescence caused by the collision of oxygen molecules. For more
    information consult the website.
    http://www.unisense.com/MicroOptode

    A oxygen microsensor is a Clark type sensor that measures oxygen by having it diffuse through a semipermeable membrane and reacting with silver chloride to produce electricity. For more info use the link below.
    http://www.unisense.com/O2/

    To be honest I wouldn't recommend the above two as they are mainly used for research relating to blood, medicine and whatnot , as well as the fact that there is not a great deal of information on them.

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    Re: HSC Biology Marathon 2015

    I'd have to say that it is recessive as there has been a huge gap where the trait has not been present, it is definitely not dominant as it has only appeared three times and the chances of it being sex linked is relatively low as only 1/7 of the males born have the trait and they have a 50% chance of getting it.

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    Re: HSC Biology Marathon 2015

    Quote Originally Posted by Fiction View Post
    The main one I learnt, personally wasn't haemogloblin but perflurochemicals

    Artificial blood can be advantageous over real blood as there is a shortage of real blood, a need for real blood to be cross-matched as certain blood types reject blood from other blood types due to the antigen contained within red blood cells, a need for there to be an absence of infectious agents and lastly as artificial blood often have a longer shelf life than real blood (e.g Perflurochemicals last for 12 months compare to real blood which has a shelf-life of around 3 months).

    An example of artificial blood is Perflurochemicals. It is completely sterile and disease-free as it does not contain any biological materials, it has a longer shelf life than real blood of approximately 8 more months, it can be stored at room temperature hence making it suitable to be transported conveniently in emergency vehicles such as ambulances, furthermore perflurochemicals can be used universally with all blood types, is cheaper to produce compared to using real blood, is able to dissolve 5 times more oxygen than real blood. An example of Perflurochemicals is Oxycyte TM which is currently under trial.

    Disadvantages associated with perflurochemicals include that it's around 70x smaller than real blood, hence allowing it to pass through places where real blood would not normally be able to travel in, it's need to be mixed with lipids to form an emulsion that can be mixed with blood and how it can only be used to replace the function of Red blood cells, essentially, as perflurochemicals are not able to act as disease-fighting instruments, such as white blood cells are, nor are they able to act as clotting agents, like platelets.

    Therefore, although real blood is disadvantageous over artificial blood in it's cost-efficiency, artificial blood with current technology, is not able to fully replace all functions of real blood, and because of it's size, may affect metabolic processes in the body.
    An advantage is that artificial blood reduces blood born diseases such as AIDS and hepatitis, in addition it is also non specific and can be used for anyone rather than people with weird blood types e.g a person with O- can only get blood from another person with O- blood.

    A disadvantage is that artificial blood is currently expensive to produce and it has some side effects such as increased chance of heart attacks.

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    Re: HSC Biology Marathon 2015

    Interesting question: Name ONE technology that could be used to establish evolutionary relationships and explain how the data revealed by this technology can be used to establish evolutionary relationships. (3 marks)

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    Re: HSC Biology Marathon 2015

    Quote Originally Posted by astab View Post
    Is that what your answers say? I'm not entirely convinced that it's recessive.
    Agreed with what blue gas said. If it doesn't appear in all generations, then it must be recessive as recessive alleles are masked by the dominant allele. Why don't you think that it's recessive?

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    Re: HSC Biology Marathon 2015

    Quote Originally Posted by useless stick View Post
    I'd have to say that it is recessive as there has been a huge gap where the trait has not been present, it is definitely not dominant as it has only appeared three times and the chances of it being sex linked is relatively low as only 1/7 of the males born have the trait and they have a 50% chance of getting it.
    What?

    It's not sex-linked because as both males and females can be affected, then it must be on the X chromosome. Then if you look at the female in generation IV, for the affected characteristic to be sex-linked, her father must also be affected since the characteristic occurs on the X chromosome and her mother must be either a carrier or an affected individual. Neither her parents are affected, therefore the characteristic cannot be sex-linked.

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    Re: HSC Biology Marathon 2015

    Hello children
    Quote Originally Posted by Melancholia View Post
    From time to time I feel lost inside this melody
    It's like a fantasy, except it's called reality
    HSC Aim: 95+ ATAR (Achieved) | Course: USYD Commerce (Co-op) | Current work: Big 4 Acct. Firm



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    Re: HSC Biology Marathon 2015

    Quote Originally Posted by obliviousninja View Post
    Hello children
    Hello there, sorry to put you under pressure already but why don't you take a shot at the above pedigree question?

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    Re: HSC Biology Marathon 2015

    Here is a question:

    Evolution:
    A) is a gradual change in the chemistry of the environment
    B) is a gradual change in the physical makeup of the environment
    C) is the response of organisms to changes in the environment where the fittest survive
    D) was invented by Charles Darwin and has been in use since 1859

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    Re: HSC Biology Marathon 2015

    Quote Originally Posted by DepressedPenguino View Post
    Here is a question:

    Evolution:
    A) is a gradual change in the chemistry of the environment
    B) is a gradual change in the physical makeup of the environment
    C) is the response of organisms to changes in the environment where the fittest survive
    D) was invented by Charles Darwin and has been in use since 1859
    A and B are definitely wrong, because there's two types of evolution, there's Punctuated Equilibrium (when changes happen rapidly) and gradualism (where changes happen gradually over time), so saying evolution happens gradually is not entirely correct. D may also be wrong because he may have invented evolution, but Wallace also proposed a similar theory to evolution. So we're left with C and that seems to be most likely the correct answer.

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    Re: HSC Biology Marathon 2015

    Quote Originally Posted by BlueGas View Post
    A and B are definitely wrong, because there's two types of evolution, there's Punctuated Equilibrium (when changes happen rapidly) and gradualism (where changes happen gradually over time), so saying evolution happens gradually is not entirely correct. D may also be wrong because he may have invented evolution, but Wallace also proposed a similar theory to evolution. So we're left with C and that seems to be most likely the correct answer.
    yep that's correct

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    Exalted Member BlueGas's Avatar
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    Re: HSC Biology Marathon 2015

    Quote Originally Posted by DepressedPenguino View Post
    yep that's correct
    Is this a past HSC question? Because even though C is most likely to be the correct answer, the last part of the answer refers to natural selection.

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    Re: HSC Biology Marathon 2015

    Question:

    In a species of plants there are three possible flower colours: red, blue and purple. When plants with red flowers are crossed with plants with purple flowers the resulting offspring have either red flowers or purple flowers. What is this mode of inheritance called?

    A) Sex linkage
    B) Recessive
    C) Codominant
    D) Dominant

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    Re: HSC Biology Marathon 2015

    Quote Originally Posted by BlueGas View Post
    Is this a past HSC question? Because even though C is most likely to be the correct answer, the last part of the answer refers to natural selection.
    yeah idk :/ but i dont think natural selection is a "response" tho.

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    Re: HSC Biology Marathon 2015

    Quote Originally Posted by DepressedPenguino View Post
    Question:

    In a species of plants there are three possible flower colours: red, blue and purple. When plants with red flowers are crossed with plants with purple flowers the resulting offspring have either red flowers or purple flowers. What is this mode of inheritance called?

    A) Sex linkage
    B) Recessive
    C) Codominant
    D) Dominant
    Tricky question, all I know that is that the inheritance can't be co-dominant because if it was, the offspring should have both colours in their appearance, but in this case, they are either red or purple.

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    Re: HSC Biology Marathon 2015

    Quote Originally Posted by DepressedPenguino View Post
    Question:

    In a species of plants there are three possible flower colours: red, blue and purple. When plants with red flowers are crossed with plants with purple flowers the resulting offspring have either red flowers or purple flowers. What is this mode of inheritance called?

    A) Sex linkage
    B) Recessive
    C) Codominant
    D) Dominant
    Anyone know the answer to this question?

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    Re: HSC Biology Marathon 2015

    Quote Originally Posted by DepressedPenguino View Post
    Question:

    In a species of plants there are three possible flower colours: red, blue and purple. When plants with red flowers are crossed with plants with purple flowers the resulting offspring have either red flowers or purple flowers. What is this mode of inheritance called?

    A) Sex linkage
    B) Recessive
    C) Codominant
    D) Dominant
    The answer is C;

    - You can pretty much cancel out A) as the question says nothing on females/males (I don't think they can do that to us...)
    - B) is wrong as well, as you can't have two plants, heterozygous or homozygous(recessive) red/purple and produce offspring of both colours (punnet squares! heterozygous means theres a dominant gene in there and homozygous recessive would ultimately produce a mix of both recessive genes)
    - D) is the same reasoning as why B) is wrong!

    If you think about it, they aren't going to say three colours (ie; red, purple, blue) if it has no impact on the question (this is my logic, I doubt it would work for every single question in the hsc).

    Hope that helped!
    Fiction likes this.

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    Exalted Member BlueGas's Avatar
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    Re: HSC Biology Marathon 2015

    Quote Originally Posted by brianchau3 View Post
    The answer is C;

    - You can pretty much cancel out A) as the question says nothing on females/males (I don't think they can do that to us...)
    - B) is wrong as well, as you can't have two plants, heterozygous or homozygous(recessive) red/purple and produce offspring of both colours (punnet squares! heterozygous means theres a dominant gene in there and homozygous recessive would ultimately produce a mix of both recessive genes)
    - D) is the same reasoning as why B) is wrong!

    If you think about it, they aren't going to say three colours (ie; red, purple, blue) if it has no impact on the question (this is my logic, I doubt it would work for every single question in the hsc).

    Hope that helped!
    Yeah the answer is C, but the question is worded poorly in my opinion. "The resulting offspring has either red OR purple", by using OR that means it only has ONE of them at a time, if it said AND instead of OR, then that means they would have both colours in their appearance, and the answer would definitely be C.
    Queenroot likes this.

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    Re: HSC Biology Marathon 2015

    Quote Originally Posted by BlueGas View Post
    Anyone know the answer to this question?
    from my answer sheet, it is C

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    Re: HSC Biology Marathon 2015

    How does the amino acid attached to the tRNA gets accumulated onto another amino acid (attached to another tRNA) during translation? Is it through an enzyme? If so, anyone knows the name of it?

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