Mitosis and Meiosis

Mitosis

A process of cell division that results in two genetically identical daughter cells from a single parent cell.

Are cells always undergoing mitosis?

No, cells only undergo mitosis during specific phases of their life cycle, particularly for growth, repair, and asexual reproduction.

Are cells always undergoing meiosis?

No, meiosis occurs only in specific cells for sexual reproduction, producing gametes such as sperm and eggs.

stages of cell growth and division

Interphase: G1, S Phase, G2…Mitosis: Prophase, Prometaphase, Metaphase, Anaphase, Telophase

Meiosis

A specialized form of cell division that reduces the chromosome number by half, producing four haploid gametes from one diploid cell.

Sister Chromatids

Identical copies of a chromosome that are formed by DNA replication (s phase) and are joined at a single point called the centromere…Each chromatid contains an identical DNA sequence…ensure that when a cell divides during mitosis or meiosis, each resulting daughter cell receives an exact copy of the chromosome

Homologous Chromosomes

Pairs of chromosomes that have the same structure and gene sequence but may carry different alleles…Each pair consists of one chromosome inherited from the mother and one from the father…allow for crossing over and independent assortment = genetic diversity.

G1

The first phase of interphase in the cell cycle, during which the cell grows and prepares for DNA replication.

Interphase

The phase of the cell cycle in which the cell is not actively dividing but is preparing for mitosis or meiosis by undergoing DNA replication and growth…G1, S Phase, G2.

G2

The second growth phase of interphase, where the cell continues to grow and prepares for mitosis by producing proteins and organelles.

S phase

The phase of interphase where DNA is replicated, resulting in two sister chromatids for each chromosome.

Prophase

The first stage of mitosis and meiosis, where chromosomes condense and become visible, and the mitotic spindle begins to form.

Prometaphase

The stage following prophase in mitosis and meiosis, where the nuclear envelope breaks down and spindle fibers attach to the chromosomes at their kinetochores.

Metaphase

The stage of mitosis and meiosis where chromosomes align at the cell's equatorial plane, ensuring they are properly attached to the spindle fibers for separation.

Anaphase

The stage in which sister chromatids are pulled apart and move toward opposite poles of the cell.

Telophase

The final stage of mitosis and meiosis, characterized by the reformation of the nuclear envelope and the de-condensation of chromosomes.

What phase are genes packed as chromatin

Interphase

What phase are genes packed in chromosomes

Mitosis

Crossing Over

A process during prophase I of meiosis where homologous chromosomes exchange segments, increasing genetic diversity in gametes.

diploid/2n cell

A cell that contains two complete sets of chromosomes (1 mom, 1 dad), one from each parent, typically found in somatic cells.

how many chromosomes do humans have

Humans have 46 chromosomes, arranged in 23 pairs, with one chromosome of each pair inherited from each parent…2n

homologous chromosomes vs. sister chromatids

Homologous chromosomes are pairs of chromosomes, one from each parent, that are similar in shape, size, and genetic content...may carry different alleles, allowing for genetic variation…align and exchange genetic material during meiosis, particularly during prophase I, called crossing over.

Sister chromatids are identical copies of a single chromosome, created during DNA replication, and are joined together at the centromere…Each chromatid has the same genetic information…separate during mitosis or meiosis II, ensuring that each daughter cell receives an identical set of chromosomes.

does information carried on homologous chromosomes have to be identical?

No, they may carry different alleles.

during mitosis each cell gets

equal and identical genetic info as the original cell…no loss of info

If chromosomes where formed at all times then we would expect

a continuous and uniform distribution of genetic information, leading to reduced genetic diversity…constant and unregulated increase in genetic material within the cell. This could lead to several issues, such as genomic instability, difficulty in proper segregation of DNA during cell division, and an increased likelihood of mutations or cancer.

Mitosis and Meiosis differences

1. Purpose: Mitosis is primarily for growth, tissue repair, and asexual reproduction, producing two genetically identical daughter cells from a single parent cell. In contrast, meiosis is specifically designed for sexual reproduction, resulting in four genetically diverse haploid gametes from one diploid cell.

2. Number of Divisions: Mitosis involves one division cycle (prophase, metaphase, anaphase, and telophase), while meiosis consists of two division cycles: meiosis I (reduction division) and meiosis II (similar to mitosis).

3. Chromosome Number: Mitosis maintains the same chromosome number in the daughter cells as the parent cell (diploid to diploid), whereas meiosis reduces the chromosome number by half, going from diploid to haploid.

4. Genetic Variation: Mitosis results in daughter cells that are genetically identical to the parent cell and each other, whereas meiosis introduces genetic variability through processes such as crossing over during prophase I and independent assortment during metaphase I.

5. Sister Chromatid Separation: In mitosis, sister chromatids are separated during anaphase, ensuring each daughter cell receives an identical set of chromosomes. In meiosis, sister chromatids are separated during meiosis II, while homologous chromosomes are separated during meiosis I, contributing to genetic diversity.

6. Cell Types: Mitosis occurs in somatic (body) cells, while meiosis occurs in germ cells that give rise to gametes (sperm and eggs).