Most of the cells of flowering plants that we have studied so far, like the cells making up the epidermis, cortex, and vascular tissues (but not the sperm and eggs cells), are called somatic cells, and are diploid (2n). Endosperm cells have three sets of chromosomes, two from the female parent’s polar nuclei (n + n) and one from the male parent’s sperm (n), so this tissue is triploid, abbreviated 3n.

Recall that one result of double fertilization in plants is that one sperm cell unites with two female polar bodies to create the endosperm found in seeds.

When cells contain two sets of chromosomes, they are described as diploid, abbreviated 2n.

When the sperm and egg, each of which are n, unite to form a zygote, the zygote cell now has two sets of chromosomes, one from the male parent’s sperm and one from the female parent’s egg.

When cells contain one set of chromosomes characteristic of the species, this state is called haploid and is abbreviated n.

In higher organisms like plants (and animals, including humans), gamete cells (egg and sperm) typically each contain one set of each of the chromosomes found in that particular species.

Ploidy refers to the number of sets of homologous (identical) chromosomes in a cell. Recall that the mitosis phase of the cell cycle “pie” is divided into four stages we’ll look now at what happens in each of those stages and how it contributes to the outcome of mitosis, the equal division of chromosomes into two daughter cells. Here we’ll look more closely at the synthesis (S) phase of interphase and at the mitosis (M) phase.

The previous lesson focused on DNA’s ribose-phosphate backbone, on the purine and pyrimidine bases, and on how DNA complexes with protein and coils to form chromatin.

Recognize what happens to the chromosomes, cell wall, cell membrane, and nuclear membrane in each stage of mitosis.

Explain how the chromosomes prepare for cell division in the S phase of interphase.

Compare diploid and haploid and identify which cells in the plant are which.

By the end of this lesson you will be able to:

Mitosis flip book drawings interphase 1