mendelian help?

Question

when the true breeding tall red snap dragon is crossed with a true breeding dwarf white snap dragon, their offspring , teh F1 generation are tall and pink., assuming that the genes for color and height are not linked, determine th ephenotype ration expected when 2 of these tall piink snap dragons are crossed with each other.
plz show your work i appreciate that

Answer 1

I agree with the first answerer Soccer Tease except that:

1. Red and white making pink is an example of incomplete dominance rather than codominance. In codominance both forms of the trait will show in a heterozygote. Incomplete dominance means that a heterozygote has an intermediate form of the trait - like pink.

2. You have to combine the expected phenotype ratios for the two different traits. I agree that you would expect 3 tall: 1 short. And I agree that you would expect 1 red: 2 pink: 1 white. However, you can combine these by "multiplying" the two ratios together.
3 tall: 1 short
1 red: 2 pink: 1 white
----------------------------
3 tall, red: 6 tall, pink: 3 tall, white: 1 short,red: 2 short, pink: 1 short, white

Soccer Tease's method and explanation are excellent.

Answer 2

1/4 tall 3/4 short
1/2 pink 1/4 white 1/4 red

You can tell that the genes for the height are in a dominant-recessive relationship. Because one of the plants was TT(tall) and the other was tt (short), you know that the F1 is Tt.

When two Tts are bred together, you will get one TT, 2 Tts, and one tt. Both the Tt and the TT are tall, so you have 1/4 short(tt) and 3/4 tall(TT, Tt, tT)

Because the color of the F1 is different than the parents, you know the relationship is not simply dominant/recessive. They must be co-dominant, so RR is red, Rr is pink, and rr is white.

When two Rr are bred, the combinations you get are: RR, rR, Rr, and rr. That gives you 1/4 Red, 1/2 pink, 1/4 white