Flashcards in Mitosis and Meiosis Deck (36)
What is mitosis?
Cell division, occurs throughout the body and makes somatic cells. Helps you to grow and repair damage.
1. Not technically a phase of mitosis, but occurs before the process begins.
2. During the synthesis phase, DNA is copied, chromosomes are replicated.
3. Interphase is the resting stage, where is the cell isn't actively dividing. The cell spends the most time in this phase, and continues to perform regular cell functions.
4. Afterward, chromosomes (chromatids) have doubled, but the cell has 46 chromosomes.
Region that holds together each chromosome and duplicate piece of DNA.
An individual chromosome, or piece of DNA.
4 Stages of Mitosis
1. Centrioles move to opposite sides of the cell and form a mitotic spindle.
2. The chromosomes condense and become visible
3. Nuclear membrane begins to break up.
Organelle that helps develop spindle fibers during cell division.
Bunch of fibers formed during prophase. Attaches to chromosomes at their centromeres, and help to push/pull them during mitosis.
Equator/middle of cell.
1. Spindle fibers help chromosomes to line up at the metaphase plate.
2. Spindle fibers attach to centromeres.
3. Centrioles go to opposite poles.
Area where the cell pinches inward.
1. Centromere splits in two, so each chromatid separates from its partner.
2. Spindle fibers shorten and move new chromosomes to opposite sides of the cell.
3. Cell begins physically splitting in two
1. A nuclear membrane forms in each new cell
2. 2 identical daughter cells result, each with 46 chromosomes.
3. Cytokinesis occurs
4. Afterward, daughter cells enter interphase.
Cytoplasm divides, occurring during telophase
Where does mitosis occur in plants?
Only occurs in meristems (growing regions).
Found at tip of stem and tip of root, allows for growth in length.
Allows for growth in width.
One gene- one protein theory
A gene is a portion of a chromosome that gives rise to one protein molecule. A chromosome contains many genes and could create hundreds of proteins.
A gene is expressed when it creates a protein. A gene is a portion of a chromosome.
The amount of chromosomes is half that of the diploid number. 23 in humans. Sex cells (sperm and ova) are haploid.
1. Diploid cell
2. Formed when a sperm fertilizes an ovum, and begins to undergo mitosis.
What occurs during meiosis?
1. The cell undergoes DNA replication during interphase, like during mitosis. At this point, the cells still have 46 chromosomes.
2. Replicated chromosomes are split up over the course of 2 sets of divisions.
3. First set of division establishes differences between mitosis and meiosis.
Homologous chromosomes line up. 1a finds 1b, etc, forming 23 pairs. These chromosomes are not identical. Consists of 4 chromatids (a tetrad).
1. Normal prophase events occur: chromosomes condense.
2. Synapsis occurs
3. Crossing over takes place- like segments on homologous chromosomes are exchanged
New chromosomes created by crossing over, which causes variety among offspring. Also means that gametes are not identical, unlike daughter cells created by mitosis.
1. Chromosomes still line up in the middle of the cell, but they stay in pairs. 23 pairs line up.
2. Independent assortment of chromosomes- the way that chromosomes line up during this phase affects the outcome of genetic information in gametes.
3. Genes on non homologous chromosomes are inherited independently, linked genes on the same chromosome are inherited together, but can be separated by crossing over.
1. In meiosis, the centromeres do not divide
2. Homologous pairs separate. A pair of chromatids and a centromere move to opposite sides of the cell.
1. Cells still finish cytokinesis, nuclear membranes form
2. The two new cells have 23 replicated chromosomes of 2 identical chromatids, making them haploid by this phase.
1. Nearly identical to mitosis
2. In interphase 2, the chromosomes don't replicate.
3. The cells are starting with 23 replicated chromosomes
4. Forms 4 haploid cells that stop dividing unless fertilization triggers new cell cycles.