Biol10005 MST practice question help

[LeviLamp]

Yes, but it doesn't mean I remember much about them
(Thanks for responding, by the way:)))

[LeviLamp]

Thoughts on today's MST:
fuck youuuuuuuuuuuuuuuuuuuu Biology department
I studied all weekend but that was actually the worst thing 

[hobbitle]

Thoughts on today's MST:
fuck youuuuuuuuuuuuuuuuuuuu Biology department
I studied all weekend but that was actually the worst thing 

LeviLamp, had you done the practise question set?  Was the MST harder than the practise questions?

[LeviLamp]

I only got one of the practice questions wrong; the MST was significantly harder (but not in a straightforward way , it was just shittily designed so it didn't really matter how much of the theory you knew). That said, other versions might be much better? (I had Test C)

[hobbitle]

I only got one of the practice questions wrong; the MST was significantly harder (but not in a straightforward way , it was just shittily designed so it didn't really matter how much of the theory you knew). That said, other versions might be much better? (I had Test C)

That's depressing, I got about 5 of the practise questions wrong.  Bummer.

[simpak]

MIIM30003 today = >:

[LeviLamp]

simpak gosh how COULD you this thread is for BIOL10005 only
!!!
(you'll get a good mark I'm sure)

[simpak]

Oh nah I'd already had it, it was at 9am.  I seriously suck at exams that early, no matter when I go to bed and when I get up my brain only starts becoming useful around 9:40-9:50 and by that time a midsem is pretty much over.  And nah, fucked something up lol.

[simpak]

Nekk minute 100% mst

Nah definitely not I know I got stuff wrong upon reflection with my slides and a box of tissues.

[hobbitle]

Argh you guysssssss! Makin me freak out. Any tips for someone who still has until Friday?

[LeviLamp]

This is really pessimistic but just don't freak out too much because I promise everyone else feels the same way
I don't think I can give any study advice other than to say to look at the little details of the lectures and not the big concepts just in case it saves you in the MST. And don't freak out while doing the test due to time constraints - I did that and so I couldn't get my head around the last couple of questions I attempted.

Good luck

[MelonBar]

26. When carrying out a _2 analysis, the expected number of red snapdragons in the G2
 if there were 100 offspring is
A. 25
B. 50
C. 75
D. 100
27. When carrying out a _2 analysis the degrees of freedom value for the cross above is
A. 1
B. 2
C. 3
D. 4

Couple questions with the above 2...

What is a '_2' analysis?

How would I calculate the degree of freedom? i.e actually answer question 27.

Thanks

[hobbitle]

MelonBar...

"_2" means "Chi-squared", I think it's a formatting error in the PDF.  They probably meant to write the 'Chi' symbol and it turned it into an underscore.  We did Chi-squared tests in Prac 1, so have a look over that.

Here's a useful website: http://archive.bio.ed.ac.uk/jdeacon/statistics/tress9.html

The website explains it pretty well but the degrees of freedom is calculated by (n - 1) where n is the number of 'categories' or in our case, phenotypes red, pink, white.

You don't need to know what a chi-squared analysis is to answer Q26.  Can you answer it if you ignore the first half of the question?

[MelonBar]

Thanks for the link nicola. I understand it now !

doing the mst at 1 today lol

Gl on yours tomorrow

[hobbitle]

Hi genetics experts,

Here's a long one that I can't make head or tail of.  Can anyone help?

Females from a wild type pure breeding stock (Strain A) of Drosophila were crossed to homozygous males (Strain B) which were phenotypically white eyed.  The F1 progreny were all wild type.

F1 males were then test-crossed to white-eyed females (of strain B)

The results of the testcross progeny:
Males, all white eye, 2
Females, wild type, 1
Females, scarlet eye, 1

(A) What does the difference in phenotypes between males and females in the offspring of the test cross suggest?
(B) Do the results tell is that scarlet eye is an autosomal dominnat or autosomal recessive character?  Therefore the F1 male and the purebreeding white eye female much each carry at least one ______ allele, at the scarlet locus.


I just can't get clear in my head what is going on here.
What I THINK is:
- that there is a white-eye locus on the X chromosome making the trait X-linked recessive.
- that there is a scarlet locus on an autosome that is an autosomal recessive trait.

So in the first cross, where sc=mutation for scarlet, X^M=mutation for white eye

purebreeding wild type FEMALE: X^M+X^M+; sc⁺sc⁺     x     purebreeding(?) white eyed MALE: X^MY; sc⁺sc

F1 Progeny --> all wild type  (females X^M+X^M;sc⁺sc⁺ or  X^M+X^M;sc⁺sc  : males X^M+Y;sc⁺sc⁺ or  X^M+Y;sc⁺sc)


TEST CROSS:
White eye-d female: X^MX^M; sc⁺sc        x     F1 male (X^M+Y;sc⁺sc)

I think this must be the genotypes for the crosses but I don't know how to draw a punnet square (or something) to work out how the phenotypes would eventuate?  I haven't experienced having a combination of X-linked and autosomal influenced traits so I don't know whether would generate a 4 x 4 punnet square or a 2 x 2 punnet square one for each chromosome??

Why can't the Male offspring of the test-scross be scarlet eyed???