Final answer:
All offspring from a cross between yyrr and yyrr will be homozygous recessive (yyrr), resulting in a 100% probability of green and wrinkled seeds, as both parents can only pass on the recessive alleles for these traits.
Step-by-step explanation:
The question involves a Punnett square cross of yyrr by yyrr, which focuses on Mendelian genetics, specifically the inheritance of two separate traits where 'y' and 'r' represent recessive alleles for yellow and wrinkled seed phenotypes, respectively. In this case, since both parents are homozygous recessive (yyrr), all offspring will also be homozygous recessive (yyrr). Because each parent can only pass on a 'y' and an 'r' allele, there is a 100% probability that the offspring will be green and wrinkled (phenotype corresponding to yyrr genotype).
Applying the law of independent assortment and considering two separate genes, with each gene following a 1:2:1 genotypic and a 3:1 phenotypic ratio, is only relevant if we deal with heterozygous crosses, but in this case of homozygous parents (yyrr x yyrr), these ratios do not apply. We expect the offspring to exhibit a phenotypic ratio of 4 green, wrinkled seeds to 0 of any other phenotype—since they all carry the homozygous recessive combination.