Punnett Squares?

Question

When solving for the F2, how do you know which two genes from the F1 to combine?

for example: solve for the F2 when crossing a heterozygous tall with a homozygous short pea plant. name the phenotype and genotype.

Answer 1

If the original parents are Tt x tt, you can't really work out the F2 on paper. The F1 would be 1 Tt: 1 tt. Peas self-fertilize unless man intervenes, so half of the F1 would be Tt x Tt and the other half of the F1 would be tt x tt.

Are you sure your teacher is asking for the F2 of original parents Tt x tt? Doesn't make sense to me, and I've been teaching bio since 1973.

Answer 2

I agree with ecolink (although I don't understand what he means by the last bit - Tt x tt is obviously precisely what is being asked - and it is precisely what he/she could not answer) - the F1 are "expected to be" about 1/2 Tt and 1/2 tt (don't fall into the trap of ever saying they "will be" in certain proportions!).
I agree that your teacher seems confused. The only way to properly answer this is to give the three alternative crosses to arrive at an F2 generation: Tt x Tt, Tt x tt, tt x tt.

Answer 3

The Punnett sq. is a diagram this is used to predict the end results of a particular go or breeding test. that's named after Reginald C. Punnett, who devised the perspective, and is used via biologists to be certain the risk of an offspring having a particular genotype. The Punnett sq. is a precis of each obtainable mix of one maternal allele with one paternal allele for each gene being studied in the go.

Answer 4

hetrogenous tall means Tt (two different genes one dominant other recessive)
homogenous short means tt ( both are short that means recessive)

That makes

T t cross t t

T of hetrogenous tall will combine with t of homogenous short

T of hetrogenous tall will combine with second t of homogenous short

t of hetrogenous tall will combine with t of homogenous short

again t of hetrogenous tall will combine with second t of homogenous short

that give u combination

Tt
Tt
tt
tt
phenotypic ratio
02 tall (as they have capital T)
02 dwarf( as they have no capital T)

genotypic ratio
02 hetrogenous tall plants
02 homogenous dwarf plant.