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?

ST and St genetic combinations

Explanation:

This is a dihybrid pea plant i.e. a pea plant with two genes (S and T). The pea plant is homozygous for gene S i.e it possesses same alleles of the gene while it is heterozygous for gene T i.e. possesses different alleles for the gene.

This pea plant will undergo meiosis in order to produce its reproductive cells (gametes) which are borne in the pollen grain.

According to Mendel's law of segregation and independent assortment, the alleles of each gene get separated into gametes independently of one another i.e. alleles S and S get sorted into the gametes without affecting the sorting of alleles T and t.

The parent pea plant produces four possible gametes after meiosis: ST, St, ST, and St.

From the observation of the genotypic content of the above gametes, it is clear that there are only two distinct genotype i.e. ST and St.

Hence, ST and St are the two possible genetic combinations of gamete (pollen grain) that can be produced by pea, SSTt.

explanation:

b,bacteria convert nitrates

into nitrogen gas.

d,plants and animals take in

and use nitrogen compounds.

e,bacteria break down waste    

products and return nitrogen  

to the soil.

a,bacteria convert atmospheric

nitrogen to ammonia.

c,bacteria convert ammonia

to nitrites and nitrates.