Lab #4 Flashcards
Growth of plants occurs by what two different processes? (2)
- Expansion of exisiting cells
2. Addition of new cells by division of cells in the meristems
Cell Division (2)
- mitosis + cytokinesis
- 2N (diploid) cell divides to produce two new diplod cells which are genetically like the parent cell
Cell Division: Mitosis
Def. + 3 Process
• Division of nucleus
- Accomplished by the duplication of the genetic material to produce sister chromatids and the seperation of these sister chromatids on the spindle
• duplication of genetic material
= sister chrimatids
—> seperation of SC on spindle
Cell Division: Cytokinesis
Def + Process
• Division of the cytoplasm
- Accomplished in plant cells by the formation of the cell plate between the two divided nuclei
Homologue
2 morphologically identical chromosomes
Centromere
Each chromosome has two sister chromatids and each sister chromatid is held together by a centromere
Heterochromatin
Two sister chromatids are held together by centric heterochromatin
Mitosis Stages
- Prophase
- Metaphase
- Anaphase
- Telophase
- Interphase
- Prophase
In this stage two chromosomes are visible as long thread like structures. Each chromosome consists of two identical chromatids which for a time are joined along their length. During Prophase the chromosomes become shorter, thicker, and coiled. The spindle, which is composed of spindle fibers, forms outside the nuclear envelope which later breaks down. An unstained gap in the chromosome, the centromere, becomes visible
- Chromosomes are visible
- 2 identical chromosomes attached along their length
- become shorter, thicker, and coiled.
- The spindle, which is composed of spindle fibers, forms outside the nuclear envelope which later breaks down
- Centromere becomes visible
- Metaphase
The chromosomes are aligned at the center of the cell
- Anaphase
Centromeres seperate and the 2
Chromatids of each chromosome are pulled apart and move to opposite poles
- Telophase
The sister chromatids reach the poles and a new nuclear envelope forms around each group. At this point, the 2 daughter nuclei are seperated by the developing cell plate, which completed the process of cell division
- Interphase
The period of time between the end of the telophase of one division and the beginning of prophase of the next divisions is known as Interphase. It is during Interphase that the chromosomes duplicate so that by the start of the next division each chromosome will consist of 2 sister chromatids
Meiosis
- in the diploid somatic progenitor of germ cells there are 2 copies (morphologically but not necessarily genetically identical) of each chromosome.
- One is from the male, the other is from the female
- Homologous
- During Prophase homologues pair to form a bivalents
- a second interphase follows and the two cells produced by the first division execute a mitosis-like division
Bivalents
Arrange themselves at the equator of the cell during metaphase I and homologues seperate at Anaphase I and move to opposite spindle poles
