why do cells go through meiosis? cells go through meiosis in order to make sex cells sex cells are...
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Meiosis
Why Do cells Go through Meiosis?Cells go through
Meiosis in order to make Sex Cells
Sex cells are also called Gametes
Four Daughter Cells are created
Haploid (1N)
Interphase
Cell GrowsDuplicates DNACell Prepares to divide
After InterphaseIn order to make sex cells or cells with half
the number of chromosomes meiosis has TWO phases
Meiosis I and Meiosis II
Prophase IChromosomes
Condense (visible)Homologous
chromosomes form a tetrad
Crossing Over Occurs
Crossing OverHomologous
Chromosomes- Similar Chromosomes, Same genes in the same location
When the chromosomes touch they switch genes
Causes genetic variation
Metaphase I Homologous
chromosomes move together to the middle of the cell
Spindle attaches to the centromere
Anaphase IHomologous
chromosomes separate
Sister chromatids stay attached
Move towards opposite poles
Telophase IDivision of
cytoplasmCreates Two
daughter cellsBegin Meiosis IIThere is no
interphase IIWhy?
Prophase IISpindles re-appearNuclear membrane
stays separated
Metaphase IIChromosomes line
up in the middleSpindle attaches
How are metaphase I and II different?
Anaphase IISister Chromatids
Separate from each other
How are Anaphase I and II different from each other?
Telophase IINucleus reformsDivision into four
daughter cellsHaploid (1N)Gametes (egg and
sperm)
Mitosis & the Cell Cycle
Cell Growth & Development
Are cells of organisms the same size? Do your cells get bigger as you grow, or do you just produce more cells?
When talking about Cell Size…… Smaller is Better!
The larger a cell becomes, the more demands the cell places on its DNA, and the harder it is to supply with nutrients.
Cell Division Before a cell becomes to large, a
growing cell will divide. Cell division is the process by which
a Single cell divides into 2 Daughter cells.
Cell Division = the series of events that cells go through as they grow and divide.
Chromosomes Chromosomes=
are composed of DNA-Which carries the cell’s coded genetic information.
Humans have 46 chromosomes(23 pairs).
The chromosomes consist of two identical sister chromatids.
Two Major Types of Cell Division
Mitosis- Somatic cells (Body Cells) Diploid 2N
Meiosis- Sex cells/ Gametes Haploid 1N
Mitosis Mitosis is the process by which the
genetic information is replicated and distributed to daughter cells.
2 diploid(2N) daughter cells are produced from 1 diploid (2N) parent cell.
The Daughter cells are genetically identical to the parent cells.
There are 4 major stages to mitosis, Not including interphase.
Interphase Interphase= The cell spends most of
its life here; not part of the actual reproduction. NOT PART OF MITOSIS. Cell grows and replicates its DNA and
centriole Nuclear membrane is visible Nucleus, Nucleoli, and chromatin can
be seen.
Interphase
Prophase Prophase: first
phase of Mitosis Nuclear membrane
breaks down Chromosomes
become visible Centrioles
separate Spindle forms
Metaphase Metaphase:
Second part of Mitosis Chromosomes
attach to spindle Chromosomes line
up across the MIDDLE of the cell
Anaphase Anaphase: Third
step in Mitosis The sister
chromatids separate and move apart towards opposite poles
Telophase Telophase: Fourth
stage of Mitosis Chromosomes
gather at opposite ends of the cell
The nuclear membrane begins to form and enclose the chromosomes
Cell membrane begins to move inwards
Cytokinesis Cytokinesis: Final
stage in cellular division
Not Mitosis Works with
telophase The cytoplasm
divides completely in half.
2 daughter cells with identical genetic information are produced.
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