0:01 the process of cell division that
0:04 results in gametes is known as meiosis
0:07 sometimes known as reduction division we
0:09 refer to gamet as sex cells such as
0:12 sperm in men and egg in women meiosis is
0:15 divided into the meiosis one stage and
0:17 the meiosis 2 stage of cell division
0:20 there are four phases in meiosis 1
0:23 prophase 1 metaphase 1 anaphase 1 and
0:25 telophase 1
0:27 additionally there are four phases in
0:30 meiosis 2 prophase 2 metaphase 2
0:35 anaphase 2 anaphase 2 meiosis 1 now
0:37 let's focus on the first stage of
0:40 meiosis known as meiosis 1 prophase 1
0:42 commences with a diploid cell its
0:44 chromatin contains two sets of
0:47 chromosomes one inherited from each
0:50 parent during this phase the DNA and the
0:52 chromatin replicates and condenses into
0:55 recognizable x-shaped chromosomes and
0:58 its identical sister chromites of each
1:00 chromosome the chromosomes couple up
1:02 with their corresponding counterparts in
1:04 a fascinating process called synapsis
1:06 generating a tetrad made up of four
1:09 sister chromites the true magic now
1:12 begins with crossing over segments of
1:14 alal swap across chromatids during this
1:16 genetic exchange event creating brand
1:17 new Gene
1:20 combinations as meiosis 1 progress the
1:22 nuclear membrane vanishes and spindle
1:31 chromosomes metaphase 1 the moment of
1:33 alignment where homologous chromosomes
1:35 line up at the cells
1:37 equator then comes anaphase 1 and the
1:39 spindle fibers diligently separate the
1:42 homologous chromosomes in each tetrad
1:43 pulling them to opposite poles of the
1:46 cell with til Phase 1 one chromosome
1:48 from each homologous pair takes position
1:50 at separate poles although they still
1:53 remain in the form of sister chromites
1:55 however each chromosome is still
1:57 composed of sister chromites
1:59 remember that the sister chromites of
2:01 each chromosome are no longer identical
2:03 due to AIC exchange and
2:05 crossovers the spindle fibers then
2:07 disappear and the nuclear envelope
2:09 reforms around the
2:13 chromosomes finally cyto canis occurs
2:15 meiosis one ends with two genetically
2:18 distinct haid daughter cells each haid
2:20 cell contains only one set of
2:22 chromosomes consisting of paired sister chromites
2:23 chromites
2:26 both cells now enter the next stage meiosis
2:27 meiosis
2:30 2 however unlike meiosis 1 DNA is not
2:34 replicated until meiosis 2 begins also
2:36 in prophase 2 the nuclear envelope
2:38 disappears and spindle fibers fan out
2:40 from the two sets of paired
2:42 centrioles during metaphase 2 the
2:44 chromosomes in each cell align at the
2:46 equator and attach to spindle fibers at
2:49 either pole during anaphase 2 the sister
2:51 chromites of each chromosome separate
2:54 and migrate to opposite poles once the
2:56 sister chromed separate they are called
2:59 chromosomes finally in Tila Phase 2 the
3:01 spindal fibers disappear the nuclear
3:04 membrane regenerates and both cells
3:05 undergo cyto
3:07 canis meiosis 2 ends with four
3:10 genetically distinct haid daughter cells
3:11 each containing only one set of chromosomes
