MEIOSIS

• Meiosis – the second type of cell division which is intended for sex cells or gametes only.
• function of meiosis: to produce 4 haploid daughter cell from a single parent cell
• function of meiosis: to reduce or decrease the number chromosomes to resulting cells into half.
• function of meiosis: to produce gametes or sex cells
• Meiosis I: concentrates on reducing the diploid chromosomal number to haploid.
• Meiosis II: focuses on producing 4 daughter cells, each carrying haploid chromosomes.
• interphase- The cell duplicates everything including the DNA and chromosomes.
• interphase- nucleus is visible.
• meiosis 1: concentrates on reducing the diploid chromosomal number to haploid
• prophase 1: condensing of chromosomes
• Leptotene- formation of 2 sister chromatids
• Zygotene – pairing of homologous chromosomes based on its size and shape
• Pachytene – crossing over occurs where in a segment of a sister chromatid exchange with the same segment of its sister chromatid of the homologous chromosome. The cross linkage segment is called chiasma.
• Diplotene- uncoiling of chromosome
• Diakinesis- dispersal of paired chromosome in the nucleus.
• Metaphase I – paired chromosomes aligned at the equatorial/metaphase plate
• Anaphase I – Spindle fibers start pulling the homologous chromosomes towards the opposite poles.
• Telophase I – karyokinesis and cytokinesis occurs containing haploid number of chromosomes.
• meiosis 2: focuses on producing 4 daughter cells, each carrying haploid chromosomes
• interphase 2: resting phase, no dna replication
• prophase 2: centrosomes separate, spindle fibers form, NO crossing over
• metaphase 2: homologous chromosomes align in the metaphase plate
• anaphase 2: sister chromatids separate and move to opposite poles of the cell
• telophase 2: nuclei reforms, 2 cells are dividing resulting 4 cells
• Gametogenesis – refers to the formation, development and maturation of gametes. There are two types namely spermatogenesis and oogenesis.
• spermatogenesis- Responsible for the production of sperm cell in males.
• spermatogenesis- Occurs in the testes through meiosis
• oogenesis - process of making mature egg cells in females.
• oogenesis- Occurs in the ovaries through meiosis.
• meiosis: reduction division
• gametes- sperm and egg cells
• interphase: dna replication, cell growth nuclei is visible
• homologous chromosomes: same size, same genes
• telophase 1: new formed nuclei
• 23rd chromosome: gender
• female: xx
• male: xy
• trisomy 21 is Down syndrome, a genetic disorder that causes intellectual disability and other physical abnormalities
• trisomy 21: extra chromosome on the 21st one
• trisomy 18 is edward syndrome and its more severe than down syndrome