Science.

• Cell-In biology, the smallest unit that can live on its own and that makes up all living organisms and the tissues of the body.
• There are 5 contributors to the cell theory:

  1. Robert Hooke

  2. Anton van

  Leeuwenhoek

  3. Matthias Schleiden

  4. Theodor Schwann

  5. Rudolf Virchow
• You have learned that DNA specifies the “recipes” for all the proteins in a cell. The production of proteins is essential to life, so it stands that every cell needs a complete set of DNA instructions.
• A cell can copy its own DNA. This process must occur before the cell divides its nucleus and cytoplasm into two.
• REPRODUCTION

  Organisms must reproduce for species to persist.
• TWO TYPES:

  Asexual Reproduction Sexual Reproduction
• Why do cells divides and make more of themselves?

  ● Growth

  ● Repair

  ● Asexual Reproduction of

  Single-Celled Organisms (Binary Fission)
• What are the stages of cellular reproduction?

  ● Cellular growth and maturation

  ● Cell division
• Chromosomes

  ● rod-like structures made of DNA and protein
• 2 Kinds of proteins in chromosomes

  1. histones- proteins that DNA wraps

  around, helps hold shape of chromosome

  and allows DNA to pack tightly

  b. nonhistones- Do not aid in packing of

  DNA, instead they control specific regions of the DNA
• Parts of the Chromosome

  1. Chromatids – two identical halves of a replicated chromosome after the Synthesis phase or the S phase of the cell cycle.
• 2. Centromere – the attachment points of the two chromatids of a chromosome. It is also described as the constriction point which divides the chromosome into two sections, or “arms.”
• Chromosome

  Parts of the Chromosome

  3. Short arm – or p arm - upper arms of the chromosome which is usually shorter
• 4. Q arm - lower arms of the chromosome which is usually longer.
• A cell cycle is a series of events that takes place in a cell as it grows and divides.
• Eukaryotic Cell Cycle 2 major phases:

  • Interphase (3 stages)

  – DNA is not condensed

  • Mitosis (4 stages + cytokinesis) – Nuclear division & division of cytoplasm

  – DNA condensed
• Synthesis – replication of DNA

  – synthesis of proteins

  associated with DNA
• Gap 1 – cell grows in size

  – organelles replicated
• Gap 2 – synthesis of proteins

  associated with mitosis
• Mitosis

  Division of somatic cells (non-reproductive cells) in eukaryotic organisms.

  A single cell divides into two identical daughter cells.

  Daughter cells have same number of chromosomes as does parent cell.
• G, Checkpoint

  Check for:

  • Cell size

  • DNA replication
• Metaphase Checkpoint

  Check for:

  • Chromosome spindle attachment
• G, Checkpoint

  Check for:

  • Nutrients

  • Growth factors • DNA damage
• The Mitotic Phase

  Mitosis is divided into 4 main stages:

  Prophase Metaphase Anaphase Telophase
• prophase- ▪ DNA coils very tightly, shortening and thickening the chromosomes (condense)

  ▪ Nuclear membrane breaks into pieces

  ▪ Nucleolus disappears

  ▪ The centrosomes (an organelle that makes

  microtubules) appears and

  migrate to opposite sides. ▪ spindle fibers start to form

  and are free to attach to the chromosomes
• Metaphase

  ▪Spindle lines up the Chromosomes on the metaphase plate

  ▪Centromeres are attached to spindle fibers
• Anaphase

  ▪ Centromeres split and some spindle fibers shorten as they pull the sister chromatids toward opposite poles of the cells

  ▪ Other microtubules lengthen to move the poles apart
• Telophase

  ▪ The spindle disassembles

  ▪ Chromosomes begin to

  unwind

  ▪ Nucleolus and nuclear

  envelope form

  ▪ As this phase ends, the

  division of the genetic material is complete and the cell contains two nuclei
• Cytokinesis-After mitosis (division of nucleus), the cytoplasm splits into two (cytokinesis)

  ▪ In animal cells, cleavage furrow is developed

  ▪ In plant cells, cell plate develops
• The product of mitosis is 2 daughter cells that are identical to each other & to the mother cell
• The Daughter Cells

  ▪ In humans, the 2 daughter cells will have 46 chromosomes (23 pairs)

  ▪ Each chromosome is said to have the same gene sequence