Question

if a pea plant has a genotype SSTt, what are the possible genetic combinations that could be present in a single grain of pollen produced by the plant?

Answer 1

As you might already have learned, the gametes are formed with only one allele of each gene. You did not specify what genes the letters are,

* so lets say pea colour is determined by S/s. S is dominant for green colour, s is recisive for yellow colour.
* lets say pea form is determined by T/t. T is dominant for round pea's, t is recesive for dented peas.

Our peaplant has the genotype SSTt, what in this case would mean it has green round pea's. The genes in our plant all have two alleles. The peaform-gene determined by T/t has two allele's: 't' and 'T'

When gametes are formed only on of these alleles can end up in one gamete (so it can fuse with with another gamete that also only has one allele, and then the resulting cell will have two alleles again)

In the formation of a gamete, one allele (to be more strictly correct; one chromosome of a homologous pair) is randomly selected.

Our plant has SS Tt. So from the gene for pea color (SS) either an S or an S can be selected. From the gene for peaform (Tt) either a t or a T can be selected. The possible gametes have:
S - T
S - t

Answer 2

u know pollen means haploid