Reproductive: Asexually and Sexually
Asexual Reproduction:
2 Types of Cell division:
|
The Cell Cycle
The cell cycle begins with Interphase, where the cell grows and replicates it's genetic material.
When a cell is ready to divide, it will enter mitosis. Mitosis begins with prophase, where the nuclear membrane disintegrates, the genetic material coils into chromosomes, and the spindle begins to from from the centrioles.
The chromosomes will then be pulled to the equatorial plate of the cell by the help of the spindle. The microtubules of the spindle will attach to the centromere of the chromosomes. This is called metaphase.
The spindle will then pull the chromosomes apart. Each sister chromatid will move to opposite poles of the cell. This phase is called anaphase.
The nuclear membranes will begin to reform around the genetic material. The chromatids will uncoil and return to the form of chromatin. In animal cells, the cell membrane will pinch in to separate the nuclei into two separate but identical cells. In plant cells, a cell plate will form to separate the nuclei into two separate but identical cells. This phase is called telophase.
The process that "splits the cytoplasm" and competes mitosis is called cytokinesis, which occurs at the end of telophase.
The process that "splits the cytoplasm" and competes mitosis is called cytokinesis, which occurs at the end of telophase.
Notes:
MEIOSIS
the process that is able to produce haploid cells, or specialized sex cells (gametes) with half of the original genetic information.
Objectives:
Explain that the transfer of hereditary information (genes and chromosomes) during meiosis produces haploid cells that are not genetically identical
Explain that recombining of genetic information during fertilization produces offspring that exhibit genetic variability
Explain that the transfer of hereditary information (genes and chromosomes) during meiosis produces haploid cells that are not genetically identical
Explain that recombining of genetic information during fertilization produces offspring that exhibit genetic variability
Meiosis is able to produce sperm cells and egg cells that are used in sexual reproducing organisms.
The original cell has a full set of chromosomes (diploid or 2n)
There are 4 cells produced, each with a half set of chromosomes (haploid or n)
The original cell has a full set of chromosomes (diploid or 2n)
There are 4 cells produced, each with a half set of chromosomes (haploid or n)
The importance of meiosis is that each haploid cell that is produced is unique. In humans, the importance of such variation is that there is genetic variations among the sperm and the egg. It is because of this variation that you are not identical to your siblings, even if you share the same biological mother and father.
This image shows how each of the haploid cells varies slightly.
This image shows how each of the haploid cells varies slightly.
Meiosis: a form of cell division where diploid chromosome number produce gametes (sex cells) with haploid chromosome number. There are 2 stages...
Meiosis I
Meiosis II
Meiosis I
- reduction division
- synapsis and crossing over occur.
- synapsis: chromosomes pair up precisely with homologue so that crossing over can occur.
- crossing over- process where homologous chromosomes exchange genetic material
- crossing over- it ensures greater variety in the gametes
- Homologous chromosomes separate
- chromosomes line up at the middle randomly and separate independently (how one pair of chromosomes separate has no effect on how another pair of chromosomes separate)
- each resulting cell is genetically unique
Meiosis II
- the stage is similar to mitosis
- sister chromatids separate
- this division maintains haploid number of chromosomes
- this phase completes the goal of meiosis--producing four genetically unique cells from one original mother cell