Meiosis & Mutations S2 Flashcards
What is Meiosis?
Meiosis is the process of cell division that makes sex cells (gametes)
How many divisions and duplications are in Meiosis?
There are 2 cell divisions and 1 duplication.
How many times does the nucleus divide?
Twice
The resulting sperms and eggs have ____ the number of chromosomes found in a normal body cell (haploid).
half
Describe Interphase 1.
The chromosomes and DNA replicate, and the chromatin begin to condense.
Describe prophase 1.
Each chromosome duplicates and remains closely associated (sister cells). The chromosomes are completely condensed and (unlike mitosis) the homologous chromosomes pair with one another. Also, crossing over occurs.
What is Crossing Over?
Homologous chromosomes come together to form a tetrad; this produces genetic variation.
What is a Tetrad?
2 chromosomes or 4 chromatids (sister and non-sister)
Describe Metaphase 1.
The nuclear membrane dissolves, the homologous chromosomes attach to spindle fibers, the chromosomes are preparing to go to the opposite ends of the cell, and the chromosomes align at the equatorial plate.
Describe Anaphase 1.
The chromosomes move to opposite ends of the cell and the homologous pairs separate with the sister chromatids remaining together.
Describe Telophase 1 and Cytokinesis.
The cell begins to divide into 2 daughter cells.
Important: It’s important to know that each daughter cell can get any combination of maternal and paternal chromosomes.
Describe Prophase 2.
The cell has been divided into 2 daughter cells. DNA DOES NOT REPLICATE.
Describe Metaphase 2.
As in Meiosis 1, The chromosomes line up in the middle of the spindle fibers.
Describe Anaphase 2.
As in Meiosis 1, the chromosomes move to opposite ends of each cell and the 2 cells begin to divide.
Describe Telophase 2 and Cytokinesis.
With the formation of 4 cells, meiosis is over. Each of these prospective sex cells carries half of the number of chromosomes of somatic cells.
