Year 12s: what will be the first way you research your future options? >>

some genetics help

In pea plants, the height and colour of the peas is genetically controlled. Each pea represents a separate fertilisation event. Tall (T) is dominant to dwarf (t) and green colour (G) is dominant to yellow (g). Following a breeding experiment, the following numbers of each possible pea phenotype was found:

Tall and green: 166

Tall and yellow: 60

Dwarf and green: 55

Dwarf and yellow: 19

What is the most likely genotype of the parental plants?

I'm assuming its TtGg TtGg

does anyone know how I could work it out or if I'm right?

Reply 1

macpatgh-Sheldon

YES well done you are right - it has to be partly memory work, so you need to know that the ratios when two genotypes both have a dominant allele superceding a recessive allele, then the ratois are: 9:3:3:1 for the 4 possible phenotypes. (this is the approximate ratio in the data given in Q)

You can confirm it with a punnet square as below; if you did not know the above ratio, you would have to draw a large number of punnet squares to work it out.

So sorry unable to upload for some reason - you will need to draw your punnet sq yourself.