LG: How do we produce gametes? Date: 2/4/13. Attention: from now on, if you see any words or phrases inside this “[ ]” symbol, you need to know them by heart! . [ Mitosis] and [Meiosis]. Mitosis: - division of [ somatic cells] = [ body cells] Meiosis
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Attention: from now on, if you see any words or phrases inside this “[ ]” symbol, you need to know them by heart!
-division of [somatic cells] = [body cells]
-division of [gametes] = [sex cells]
Each resulting cell still has chromosomes from mom & dad
ONE COPIED CHROMOSOME
– each side of a replicated chromosome
-2 chromatids joined by a [centromere]
Definition: chromosomes having the same genes at the same loci (location) but possibly different alleles (alternative forms of a gene). For example, two chromosomes may have genes encoding eye color, but one may code for brown eyes, the other for blue.
sex cells (sperm)You have body cells and gametes.
The chromosomes have replicated, and they become visible.
Results in Variations!!
The homologous chromosomes attach to the spindle fibers. They are preparing to go to opposite poles.Meiosis Metaphase I
The homologous chromosomes (not chromatids) move to opposite ends of the cell.Meiosis Anaphase I
The cell begins to divide into two daughter cells. It is important to understand that each daughter cell can get any combination of [maternal] and [paternal] chromosomes.Meiosis Telophase I & Cytokinesis
The cell has divided into two daughter cells. important to understand that each daughter cell can get anyMeiosis Prophase II
Just like in Mitosis, the chromosomes line up in the important to understand that each daughter cell can get any middle on the spindle fibers.Meiosis Metaphase II
The two cells each begin to divide. As in Mitosis, the chromatids move to opposite ends of each cell.Meiosis Anaphase II
With the formation of four cells, meiosis is over. Each of these prospective gamete cells carries half the number of chromosomes of somatic cells.Telophase II &Cytokinesis
Mitosis these prospective gamete cells carries
daughter cells genetically identical to parent cell
produces 2 cells
2n 2n (diploid)
produces cells for growth & repair
no crossing over
daughter cells genetically different from parent
produces 4 cells
2n 1n (haploid)
crossingoverMitosis vs. Meiosis
MITosis takes the cell and Makes It Two (diploid)
Meiosis has to do with sex
From the cell’s point of view:
mITosis results in IdenTical Cells
mEioSis results in Egg and Sperm (haploid)
Clyde Freeman Herreid – Dept. of Biological Sciences: Buffalo State Univ. of New York
46 these prospective gamete cells carries
23Putting it all together…
meiosis fertilization mitosis + development
EMBRYO these prospective gamete cells carriesFrom one cell to many
Inner: intestines these prospective gamete cells carries
Outer: skin cells
Middle: bone cellsSpecialized cells perform specific functions.
Michael & Kirk these prospective gamete cells carries Douglas
Martin & Charlie Sheen, Emilio EstevezSexual reproduction creates variability
Sexual reproduction allows us to maintain both genetic similarity & differences.