ATAR Notes: Forum

Uni Stuff => Universities - Victoria => University of Melbourne => Topic started by: Belgarion on March 10, 2013, 08:05:07 pm

Title: Mathematics for Biomedicine
Post by: Belgarion on March 10, 2013, 08:05:07 pm: lol if one of you guys or girls can do this question, you are like god in my eyes

2.
If a certain autosomal gene has n alleles, how many genotypes are there?
Hint: count the homozygous and the heterozygous genotypes separately.
Title: Re: Mathematics for Biomedicine
Post by: ferrsal on March 10, 2013, 08:31:09 pm: I'm also interested because I couldn't do it either

The explanatory answers are ... not helpful at all
Title: Re: Mathematics for Biomedicine
Post by: Shenz0r on March 10, 2013, 08:43:58 pm: I doughnut understand how they got the solution.
Title: Re: Mathematics for Biomedicine
Post by: Belgarion on March 10, 2013, 09:55:35 pm: glad i am not the only one lol
Title: Re: Mathematics for Biomedicine
Post by: alondouek on March 10, 2013, 10:36:33 pm: I'm not at UoM, but I asked my Uncle (lecturer at Latrobe) and he texted me back this:

For an autosomal gene with $n$ alleles, the number of possible genotypes produced is $\sum ({n})$ where $n = \{1, 2, 3, ..., n\}$

So for example if $n=3$ (as in, there are 3 alleles):

$n=3$ so $\sum ({n})$ where $n = \{1, 2, 3\} = 6 possible genotypes$

i.e. $1 + 2 + 3 = 6 possible genotypes$
Title: Re: Mathematics for Biomedicine
Post by: Belgarion on March 11, 2013, 02:03:38 pm: thanks for that, but the answer says:
Title: Re: Mathematics for Biomedicine
Post by: psyxwar on March 11, 2013, 03:55:23 pm: Quote from: 2smart4u on March 11, 2013, 02:03:38 pm
thanks for that, but the answer says:
The two are equal though - just try subbing in values of n.
Title: Re: Mathematics for Biomedicine
Post by: golden on March 11, 2013, 05:31:44 pm: The answer is right, but the solutions aren't exactly corresponding with what's happening. The heterozygous part for example is wrong.
For this one, you're better off going with intuition or what alondouek suggested. There are even more ways but say in an exam situation you wouldn't want to derive many rules or use something more complicated that you can just do with a shorter method.

I didn't do Mathematics for Biomedicine as it was released this year, but I would say it's more of a multiple choice type of question (if it were in the actual exam) and would better suit a quick, short, lower probability of making mistake method.
Title: Re: Mathematics for Biomedicine
Post by: thushan on March 11, 2013, 05:48:52 pm: Hmm. I looked at the answer, and it looks fine to me. I THINK they meant an equal sign where they put the minuses through.

n homozygous genotypes.

you can choose nC2 = n(n-1)/2 combinations of heterozygous genotypes.

Hence ans = n - (n-1)/2 = n(n+1)/2

And this is equal to 1+2+3+...+n; remember in adding a series that we go 1+2+3+4...+n = ((first term) + (last term))/2 x number of terms = (n+1)/2 x n = n(n+1)/2.
Title: Re: Mathematics for Biomedicine
Post by: Kaille on March 11, 2013, 06:04:18 pm: Quote from: Rexxy on March 11, 2013, 05:48:52 pm
Hmm. I looked at the answer, and it looks fine to me. I THINK they meant an equal sign where they put the minuses through.

this is true. my copy says equal where there is a minus sign
Title: Re: Mathematics for Biomedicine
Post by: kamil9876 on March 11, 2013, 06:51:49 pm: The "- instead of =" is a recent issue that I have in my current firefox pdf viewer (i,e when i read a pdf in the browser window). However after downloading the document and reading it from my pdf viewer there is no issue and the formatting looks a lot nicer.
Title: Re: Mathematics for Biomedicine
Post by: ferrsal on March 16, 2013, 10:05:22 pm: I hate this subject :(

Tutorials help me out, and then the next lecture comes, and Bam, I'm lost and confused.