Cell Divison

Growth

An organism growing larger over its lifespan.

Repair

The process of fixing damaged tissues or cells in an organism.

Specialization/differentiation

The process where a single, unspecified cell develops into various types of specialized cells.

Gametogenesis

Generation of sperm and eggs (gametes).

Cancer

Unregulated cell division that results in this. Start out as normal body cells. Undergo genetic mutations. Lose the ability to control their own division. Grow uncontrollably, causing disease by disrupting healthy function of an organ/tissue.

Interphase

Most of a cell’s life cycle. During mitosis, growth and duplication of DNA occurs. G1 phase: growth, increase in cytoplasm (doubles cytoplasm). G2 phase: growth, preparation for division (doubles organelles). S phase: duplication of chromosomes (S stands for DNA Synthesis). G0 phase: the cell is not actively growing or dividing During meiosis I, it is nearly identical. G1 cell grows, S: DNA synthesis and G2: material inside cell (organelles, proteins) doubles. During meiosis II, DNA is not doubled. Chromosomes are still in their dyad (X-shaped) form, where each sister chromatid is identical to the other sister chromatid.

G1 phase

Growth, increase in cell size (double cytoplasm).

S phase

Duplication of DNA (S stands for DNA).

G2 phase

Growth, preparation for division (double organelles).

Cell division/M phase

The phase during which the cell divides its nucleus and cytoplasm, resulting in two daughter cells.

Mitosis

Division of the nucleus and DNA.

Cytokinesis

Division of cytoplasm and cell membrane, cells finally divide.

G0 Phase

When a cell is not actively growing or dividing, it is said to be this.

Cell cycle

Main way cell division is resulted.

Cyclins

Other proteins, that are required to go to the next stage of the cycle.

Chromatin

DNA gets wrapped into a shape called this.

Chromosomes

The whole structure of a single polymer of DNA that forms a coil of coils (a supercoil).

X-shaped chromosome

A chromosome that is made of a single chromatid (after DNA is split in the middle of mitosis), it is a monad, and this letter shaped.

I-shaped chromosome

A chromosome that contains two sister chromatids (after S phase, before the middle of mitosis), it is a dyad, and this letter shaped.

Sister chromatids

Identical pairs that are linked by a centromere, and are a result of DNA synthesis during S phase.

Homologous pair (of chromosomes)

Organisms which perform sexual reproduction have pairs of. chromosomes. One from the mother, and one from the father. Homologous refers to being in a matched pair: chromosome 1 will always have the same types of genes, even if everyone’s chromosome 1 is different. If an organism has two of the same sex chromosome, they are also a homologous pair (X and Y are not considered a homologous pair).

Body (somatic) cells

Have pairs of chromosomes, and are referred to as diploid (2n).

Sex (gamete) cells

Only have one of each chromosome, and are referred to as haploid (1n).

Mitotic spindle/spindle fibers

Required to divide the chromosomes. Attaches to the centromere of a chromosome using a group of proteins in the centromere called a kinetochore.

Nucleus

What gets divided into two identical nuclei with identical DNA/chromosomes during mitosis. As well as, reforms during telophase in mitosis.What gets divided into two identical nuclei with identical DNA/chromosomes during mitosis. As well as, reforms during telophase in mitosis.

Prophase

During mitosis, Chromatin condenses into chromosome form: Chromosomes are X-shaped dyads with two chromatids each because DNA doubled during S phase. Centrosomes form and begin creating spindle fibers, which attach to chromosomes. Nuclear envelope (membrane) and nucleolus break down. During meiosis(Prophase I), everything is the same, but synapsis and crossing over occur during Prophase I. During meiosis II (Prophase II) everything is the same as mitosis, but it happens with two daughter cells that are haploids.

Metaphase

During mitosis, Spindle fibers move chromosomes to the middle of the cell. Chromosomes line up at the middle of the cell, with one chromatid on each side of the metaphase plate. During meiosis (Metaphase I), Tetrads (pairs of chromosomes) align at equator/ metaphase plate. Independent assortment occurs: Chromosomes organize randomly. During meiosis II (metaphase II), chromosomes line up at the equator like in mitosis. However, it happens with a haploid number of chromosomes, and happens to two daughter cells.

Metaphase/mitotic plate/equator

The middle of the cell, where spindle fibers move chromosomes to. Chromosomes line up down this mitotic plate(middle of the cell).

Anaphase

During mitosis, Chromosomes separate from one another, pulled apart by the mitotic spindle. Chromosomes are divided into two daughter chromosomes (no longer sister chromatids, they are now “I-shaped” monad chromosomes instead of “X-shaped” dyad chromosomes). Chromosomes move to opposite poles of the cell. During meiosis(Anaphase I), homologous chromosomes separate and move towards opposite poles. Unlike in anaphase of mitosis, sister chromatids remain attached. Anaphase I moves X-shaped chromosomes away from each other, and doesn’t separate sister chromatids. During meiosis II (anaphase II), sister chromatids separate, dyads are split into one-armed daughter chromosomes. It is similar to mitosis, except it happens to two haploid cells instead of one diploid cell

Telophase and cytokinesis

During mitosis, Nuclear envelope reforms. Chromosomes uncoil into chromatin form. Spindle disappears. Cytokinesis, divides cytoplasm into two different cells. During meiosis (Telophase I + Cytokinesis), Each daughter cell gets a haploid (1n) number of chromosomes. There are no pairs of chromosomes in the daughter cells of meiosis I. Cytokinesis occurs and two haploid daughter cells are made. Sister chromatids are still attached to one another; chromosomes are still X-shaped. During meiosis II (telophase II/ cytokinesis II), telophase is similar to telophase of mitosis. However, happens with two daughter cells, each haploid. Cytokinesis, divides two daughter cells into four daughter cells.

Ploidy/number of chromosomes

During mitosis, diploid (2n) is produced. During meiosis, haploid (1n) is produced.

What type of cells does meiosis make, and how is that different from mitosis?

Meiosis makes 4 haploid cells. Mitosis makes two diploid cells.

What number of chromosomes do those cells have?

Diploids have 46 chromosomes. Haploids have 23 chromosomes.

How many cell divisions are involved, and why does that make a different number of cells?

Mitosis involves one cell division resulting in two identical daughter cells. Meiosis involves two cell divisions producing four daughter cells with half the number of chromosomes as the parent cell.

Are these cells different or the same (and how is that different?)

They are different: a haploid cell contains only one set of chromosomes, while a diploid cell contains two sets of chromosomes, meaning they are distinct from each other in terms of chromosome number. They are different: a haploid cell contains only one set of chromosomes, while a diploid cell contains two sets of chromosomes, meaning they are distinct from each other in terms of chromosome number. 

What lines up at the metaphase plate, and what is divided?What lines up at the metaphase plate, and what is divided?

During meiosis, Tetrads (pairs of chromosomes) align at equator/ metaphase plate. During meiosis II, chromosomes line up at the equator, just like in metaphase of mitosis. Individual chromosomes  (not homologous pairs, like in metaphase I) line up at the equator. During mitosis, chromosomes line up down the mitotic plate (middle) of the cell, with one sister chromatid on each side.

Does crossing-over/independent assortment occur?

During meiosis, crossing over occurs during Prophase I. Independent assortment occurs during Metaphase I. Neither occur, during meiosis II or mitosis.

What happens to the ploidy/number of chromosomes?

During meiosis, the ploidy level (number of chromosomes) is reduced by half. Meiosis I, divides four haploid cells chromosomes number in half (splits homologous pairs). Meiosis II, keeps chromosome (four haploid cells) number constant (splits sister chromatids). During mitosis, the number of chromosomes stays the same.