Mitosis and meiosis Flashcards
Define mitosis
Creation of 2 daughter nuclei identical to each other and to the parent nucleus in chromosome number and genetic composition
Continuous process of change
Conservative
Define meiosis
Yields 4 haploid daughter nuclei, each with half as many chromosomes as parent nucleus
All differ in genetic composition
Part of sexual life cycle
Balanced by fertilization in which 2 sex cells combine and restore the full chromosome number
Reproduction and growth in the multicellular organism requires…
The multiplication of cells
Successful multiplication requires…
That the genetic information contained in the parent cell be transferred to the daughter cells
As all genetic materials are contained within the nucleus, this process requires nuclear division
Describe interphase in mitosis
Period between successive nuclear divisions during which chromosomes are diffuse, nucleolus is present, and nuclear envelope is intact
DNA/protein complex forms chromatin
First two important things in interphase:
1) Genetic material (DNA) is replicating to provide full complement of genetic information to each daughter cell
2) Cell is building up a sufficiently large store of energy to carry through the process of division
Last two important things in interphase in mitosis:
3) New organelles are formed in order that daughter cells contain the necessary complement of organelles
4) Centrioles (in animal cells, and some protists, not plant cells) replicate so that two pairs are formed, one destined for each daughter cell
Describe prophase in mitosis
The first stage of nuclear division
Chromosomes condense from diffuse, threadlike material to discrete, compact bodies
First two important things happening during prophase in mitosis:
1) Nucleolar material disperses
2) Pairs of centrioles move away from each other to opposite ends of cell
Last two important things happening in prophase in mitosis:
3) Other microtubules running between pairs of centrioles make up the spindle (2 ends of spindle = poles, middle region = equator)
4) Individual chromatin fibers supercoiling until they are seen as distinct chromosomes
Factors of the distinct chromosomes in prophase in mitosis:
Each chromosome consists of 2 elongated structures, chromatids, associated with each other at centromere region
Each chromatid consists of a single molecule of DNA and associated proteins (histones)
Paired chromatids are…
Identical copies of each other called sister chromatids
Why is condensation of chromosomes extremely important in prophase in mitosis?
Without it, movement could not occur without entanglement
Describe metaphase in mitosis:
Centromeres of highly supercoiled chromosomes are lying on the equator
First two important things happening during metaphase in mitosis:
1) Chromosomes migrate to central plane of cell and arrange themselves along equator
2) Chromosomes attach to spindle fibers at the centromeres
Last important thing during metaphase in mitosis:
3) Chromatids move slightly apart from centromere region, sister chromatids now oriented toward opposite poles
Describe anaphase in mitosis:
Sister chromatids separate and move to poles, drawn by shortening spindle fibers
Lasts from when chromatids separate to when moving chromosomes converge at poles
First three important things in telophase in mitosis (last phase):
1) Spindle breaks down
2) Nuclear envelope reforms around each group of chromosomes
3) Chromosomes unwind and become diffuse
Last two important things in telophase in mitosis:
4) Nucleoli reappear in daughter nuclei
5) Cell divides in 2 by means of constriction of plasma membrane (in plants, it’s new formation of cell wall/plate which grows in the middle of the cell)
What happens after telophase in mitosis?
Chromosomes regain threadlike appearance and return to interphase
What is cytokinesis?
Division of cytoplasm and cell itself