Mitosis & Meiosis

Mitosis

  • mitosis is responsible for growth and repair of damage/replace worn out cells

  • a type of cell division done by most of your body cells and its really important for your cells to divide (fi they didnt divide, u wont grow)

  • mitosis is done to produce body cells

  • to heal an accident that happen to your body, u need more cells to repair it

  • mitosis makes identical cells. so if you want to replace a damaged skin cells, you need identical cells to replace what was lost.

  • interphase (growth, DNA replication, cell functions) is a clip of the cell cycle and mostly what their doing on its daily life and they are actually duplicating their DNA during interphase.

  • mitosis is a very shory amount of time to the whole cell cycle, buts its a very critical process because its where it is going to get divided and make more cells

  • nucleus (something inside your cells) holds your DNA

  • DNA is really important because its your genetic information

  • if you want to make more cells, you need to have the same DNA in your new cells like whats in you original cells (YOU HAVE TO BE IDENTICAL)

  • the main problem is that each of our body have alot of DNA so you need to organize your DNA, but DNA can be organized into condensed units called chromosomes (made our of proteins and DNA)

  • most humans have 46 chromosomes and can be found in a human body cell called nuclei (a plural of nucleus)

  • you have to duplicate those chromosomes in interphase before mitosis starts. so basically u need to duplicate your DNA (because of course you need to duplicate the materials before splitting)

  • centromere: part of chrosime where sister chromatids (strands of replicated chromosome) are held together

  • PMAT: (Mitosis Stages of Divisions)

  1. Prophase:

  • pro means before

  • where chromosomes are still there, they are still thickening and visible (condensing)

  1. Metaphase:

  • M for middle because the chromosomes line up in the middle of the cell

  • the nucleus is finally diassembled

  1. Anaphase

  • A for away because the chromosomes moves away, they are moving to the opposite side of cell (poll of the cells)

  • BUT the chromosomes isnt moving by itself, they are moving because they have something called of spindles (they help move chromosomes to the end)

  1. Telophase

  • T for two because there would be two cells in the human body, where each is going to have 46 chromosomes

  • the chromosomes are actually at the complete opposite ends and the new nuclei are forming in each side to make 2 new cells

  • nuclei starts to surround the chromosomes on both sides

  • cytokinesis: final seperation into 2 cells by spilitting which completes after the PMAT mitosis stages

Meiosis

  • contributes to genetic variety

  • makes sperm and egg cells (gametes)

  • human sperm cells and egg cells have 23 chromosomes (when they come together, they are 46 chromosomes) and that would allow new formed fertilized egg to develop into a human (zygote)

  • meiosis is a reduction division because you have a starting cell that has 46 chromosomes and you ending cells (sgametes) only have 23 chromosomes

Screenshot 2024-07-24 214538.png

  • interphase happens before process starts

  • in mitosis, PMAT is only 1x. but in meiosis, its 2x.

Screenshot 2024-07-24 215228.png

  • PMAT 1: (Meiosis First Stages of Divisions)

  1. Prophase:

  • where chromosomes are still there, they are still thickening and visible (condensing)

  • they are going to line up with their homologous pairs

  • homogolous is when chromosomes are the same size and they have the same type of genes in the same location

  • homologous is going to start matching up and its called crossing over, where they can transfer their genetic information and exhange it between each other. it makes it into recombinant chromosomes

  1. Metaphase:

  • chromosomes are going to be pairs in the middle of the cell but not in a single file line

  1. Anaphase

  • the chromosomes are going to be pulled away by the spindle fibers

  1. Telophase

  • where u finally have to 2 new nuclei and will end the meiosis stage 1 with 2 new cells

  • PMAT 2: (Meiosis Second Stages of Divisions)

  1. Prophase:

  • the spindles starts to form

  1. Metaphase:

  • the chromosomes are going to lined up in the middle and they are in a single file line (they arent in pairs anymore)

  1. Anaphase

  • the chromatids are going to get pulled away by the spindle fibers (not like anaphase 1 which the chromosomes are the one that gets pulled away)

  1. Telophase

  • nuclei starts to reform and the 2 cells are going to get divide so there would be 4 cells reforming

  • finally the cytokinesis will split the cytoplasm

Untitled

  • males produces sperm and females produces egg cells and because of independent assortment and crossing over you would have variety and thats why 2 siblings could look so different with each other

Untitled

  • nondisjunction where the chromosomes didnt seperate correctly

Comparison

making new cells:

  • mitosis: makes body cells

  • meiosis: sperm and egg cells (gametes)

starting cell:

  • mitosis: skin cell

→ diploid 2n (2 sets of chromosomes)

  • meiosis: primary spermatocyte (males), primary oocyte (females)

→ diploid 2n (2 sets of chromosomes)

PMAT:

  • mitosis: goes over once

  • meiosis: goes over twice

At the End of PMAT: cells (2 set of chromosomes, one from each parent)

  • mitosis: end with identical and diploid

  • meiosis: 4 non identical cells and gametes