Punnett square help. O_o..

[grayfalcon89]

I have few questions for the genetics. This thread can be posted on the general biology forum but especially this part is genetics, so I'm putting here I just hope it's not too easy concept if this forum only talks about complicate genetics

 

Question that I didn't understand.

 

You plant 50 yellow peas which were grown on a tall plant. When the plants mature, 28 are tall with yellow seeds; 8 are tall with green seeds. How mnay plants would you expect to be short with yellow seeds and how many would be short plants with green seeds?

 

[math]\text{Only thing I just assumed was that the genotype of the parent} [/math]

[math]\text {Which would be TtYy. The reason is that there are both}[/math]

[math]\text {Both recessive and dominant traits} [/math].

[math]\text {But my question is, how do you determine the genotype here?}[/math] And after that, I don't know what's the answer is nor do I know what should I do...

 

Questions that I did but I'm not confident [math]\bigstar[/math] indicates the questions.

 

[math]\bigstar[/math]A hetreozygous yellow-seeded pea plant is crossed with a homozygous green-seeded pea plant. One of the offspring produces yellow seeds. What is the correct genotype of the offspring?

 

Yy*yy = Yy, Yy(2), yy. So, in order for offspring to be yellow, it has to be yy so that's our answer.

 

[math]\bigstar[/math]A heterozygous yellow-seeded pea plant is crossed with a homozgyous green-seeded pea plant. There are 60 seeds produced. When these are planted, how many of the plants do you expect to produce green seeds?

 

By Yy*yy = Yy(2) and yy(2), this basically shows that green are going to be 30, which is 1/2 of 60.

 

Next three questions, in my opinion, seem all same. Maybe I'm wrong though. [math]\Rightarrow \bigstar[/math]

 

[math]\bigstar[/math]In humans, the ability to roll your tongue is controlled by one gene. A couple who can both roll their tongue has a son who cannot roll his tongue. What is the dominant version of the trait? What is the recessive version of the trait? What is the genotype of the father? mother? son?

 

Roll the tongue - dominant

Can't roll the tongue - recessive

How?

Pedigree result like:

~[]-()

~~|~

~[*]~

[] = male with no trait () = female with no shading [*] = son with shading

 

Both parents are thus, heterozygous or if the letter is used, Rr (Roll the tongue for R) and son is rr.

 

[math]\bigstar[/math]Some people have hairlines which are straight across the top of their forehead. Other people have what is called a widow's peak, a point in the center of the forehead where the hairline is lower than on either side. What is the dominant version of the trait? What is the recessive version of the trait? What is the genotype of the father? mother? daughter?

 

In case that question and one I'm going to post now is same, let me just put them together.

 

[math]\bigstar[/math]When placing your hands together, you either normally place your left thumb over your right, or your right thumb over your left, based on a single gene. A couple who both pace left over right have a daughter who places right over left. What is the dominant version of the trait? What is the recessive version of the trait? What is the genotype of the father? mother? daughter?

 

First one - Peak = dominant, straight = recessive; father and mother = heterozygous; daugher = recessive

 

Second one - Left over right = dominant, right over left = recessive; father and mother = heterozygous; daughter = recessive

 

I got these problems from the extra worksheet so they'ren't homework (that's why it's here instead of homework forum) but I'm doing this so I can understand the concept better.