AP Biology cell signaling, mitosis, cancer cells

• The main components of the learning process are attention, encoding, storage, and retrieval.
• Cell division has two functions:

  • Multicellular organisms use cell division for growth, maintenance, and repair of cells and tissues
  • Single-celled organisms use cell division to reproduce
• The cell’s DNA makes up its genome
• In Prokaryotes, the genome consists of one double-stranded, circular DNA molecule located in the nucleoid
• Additional smaller loops of DNA called plasmids may be present, which are not necessary for normal growth but may contain important information
• Exchange of plasmids with other cells allows gene transfer in prokaryotes
• The Eukaryotic Genome consists of several double-stranded DNA molecules in the form of chromosomes
• The number of DNA molecules (chromosomes) in the cell nucleus varies among species
• Somatic cells typically have 2 matched sets of chromosomes, making them diploid (2n)
• Gametes (eggs and sperm cells) have half the number of chromosomes and are haploid (1n)
• Arranging the chromosomes by size produces a karyotype
• Chromosomes that pair in reproduction of diploid cells are described as homologous
• Some genomes have pairs that don’t match, for example X and Y chromosomes in humans, which are heterologous pairs
• Eukaryotic DNA must be condensed into compact chromosomes to fit into the nucleus
• Packaging is accomplished by short stretches of DNA wrapping around a core of 8 histone proteins, forming a nucleosome
• The nucleosome structure coils to form a chromatin fiber, and fibrous proteins further pack each chromosome
• The Cell Cycle has 2 major phases:

  • Interphase (blue) is the time for normal growth and preparation for cell division
  • Mitotic phase (red) involves the replicated DNA and cytoplasm splitting and the cell dividing
• Interphase occurs in 3 stages: G1 Phase, S Phase, and G2 Phase
• The Mitotic Phase involves Karyokinesis (mitosis) and Cytokinesis, where the cytoplasmic components physically separate into 2 daughter cells
• Mitosis begins with Prophase:

  • Nuclear envelope breaks down
  • Membranous organelles disperse
  • Nucleolus disappears
  • Centrosomes migrate to poles
  • Microtubules of the spindle form
  • Sister chromatids coil tighter
• Prometaphase:

  • Sister chromatids develop a protein kinetochore
  • Chromatids attach to spindle microtubules
• Metaphase:

  • Chromosomes line up along metaphase plate
  • Sister chromatids remain attached by cohesion proteins
• Anaphase:

  • Cohesin proteins degenerate allowing chromatids to separate
  • Separated sister chromatids move in opposite directions toward the centrosomes
• Telophase:

  • Chromosomes reach opposite poles and begin to decondense
  • Spindles depolymerize into tubulin monomers
  • Nuclear envelopes form around the chromosomes
• Cytokinesis differs between plants and animals
• Positive Regulators promote movement to the next step of the cell cycle, while Negative Regulators stop advancement of the cell cycle
• Cyclins and cyclin-dependent kinases (Cdks) fluctuate predictably over the cell cycle and can be triggered by internal and external signals
• Cancer and the Cell Cycle:

  • Cancer begins with a gene mutation that results in uncontrolled cell growth
  • Proto-oncogenes can mutate into oncogenes
  • Tumor suppressor genes can prevent uncontrolled division
• Prokaryotic Cell Division:

  • Prokaryotes propagate by binary fission
• Prokaryotes, such as bacteria, propagate by binary fission
• Binary fission is the only way prokaryotes produce new individuals
• Within a species, chromosome number is consistent but may vary with developmental stage or specific cell type
• Short stretches of DNA wrap around a core of 8 histone proteins, forming a nucleosome
• The histone-DNA complex is called a nucleosome and the connecting DNA is called linker DNA
• This structure coils to form a chromatin fiber, and fibrous proteins further pack each chromosome
• The Cell Cycle is an ordered series of events in the life of a cell
• The Cell Cycle has 2 major phases: Interphase (blue) and Mitotic phase (red)
• Interphase is the time for normal growth and preparation for cell division
• Mitotic phase involves the replicated DNA and cytoplasm splitting and the cell dividing
• Karyokinesis, also called “mitosis” or nuclear division, is the first step of the Mitotic Phase