Help with dihybrid crosses...please! (1 Viewer)

[prez_shadowfax]

Hi, could someone please help me with this? I need to determine the possible genotypes for the F1 and F2 generation of the dihybrid cross TtSs X TTSS. I got stuck at F2 - there are so many of them! How do you fit all of them into a Punnett square? (I'm willing to bet there's a really simple explanation for this, but I can't seem to find anything in my textbook about it - please help, thanks!)

 

[Sepulchres]

I dont think you need to have such knowledge in year 12. As far as I know, only monohybrid crosses are in the syllabus. Correct me if I'm wrong.

 

[Natzd]

i also only think that it is monohybrid that we need to know..otherwise we'd all be inthe mess that you are in now haha, nice pick up though

 

[Sepulchres]

Heres something... http://www.sparknotes.com/testprep/books/sat2/biology/chapter7section4.rhtml

Scroll down to "The Law of Independent Assortment." Looks pretty handy.

 

[bluesky100]

Hi, could someone please help me with this? I need to determine the possible genotypes for the F1 and F2 generation of the dihybrid cross TtSs X TTSS. I got stuck at F2 - there are so many of them! How do you fit all of them into a Punnett square? (I'm willing to bet there's a really simple explanation for this, but I can't seem to find anything in my textbook about it - please help, thanks!)

Google search .

Dihybrid Cross:

It is also possible to predict the results of a cross involving parents who are heterozygous for two traits that are controlled by two different genes (TtSs X TtSs). The number can go on and on (3 or more). The predicted outcome from a cross between two dihybrid parents (TtSs X TtSs) is shown below:

TS Ts tS ts
TS TTSS TTSs TtSS TtSs
Ts TTSs TTss TtSs Ttss
tS TtSS TtSs ttSS ttSs
ts TtSs Ttss ttSs ttss

A dihybrid cross will produce offspring of nine (9) different classes with the dominant trait at both loci, three (3) with one dominant trait at one locus, three (3) with the dominant trait at the other locus, and one (1) with neither dominant trait at either locus. The phenotypic ratio is therefore (9:3:3:1).

http://hsc.csu.edu.au/biology/options/genetics/3062/genetics_973.html - more info here

Hope that helps.

 

[prez_shadowfax]

Hahaha...I'm not studying in Australia, I'm from Malaysia, but am thinking of going to Australia to study next year. I've been lurking on the forums for quite some time, just to see what the Australian education system is like...and today we were given this question for homework, so I thought I'd just ask for help here - I'm really stuck on it! Just to let you know, I'm 17 and studying in Form 5 (the last year of school for us). We do dihybrid crosses, but usually only simple ones like TTHH X tthh...but my Bio teacher likes to give hard questions...help please, anyone?

 

[Sepulchres]

Use the link or the above post.

 

[prez_shadowfax]

Ah, thanks for that - that was quick! Bluesky100, the question I was given is slightly different - it's not between heterozygous parents, but one homozygous and one heterozygous parent. Here's what I've managed to get so far:

(I apologize for any spelling errors, I don't learn Bio in English)

TtSs X TTSS

Gametes: TS, Ts, tS, ts TS

Generation F1: TTSS, TTSs, TtSS, TtSs

After that I'm stuck - too many of them

 

[rockon]

you guys doing the genetics elective? i wanted to do that but our teacher wanted us to do biotechnology.... genetics is interesting

 

[Sepulchres]

Communication tickles my pickle.

 

[Tingaling]

genetic is better!