Events from egg and sperm to embryo
Sperm fertilizes egg -> fertilized egg (zygote) goes through cell division repeatedly -> embryonic stem cells differentiate and become embryo
Specialized vs stem cells
Specialized: become tissues -> organs -> organ systems
Stem cells: undifferentiated cells that become differentiated into one or more types of specialized cells
Levels of organization from cell to organism
Organism: individual member of a species
Organ system: set of organs working together for a common function
Organ: set of tissues working together for a common function
Tissue: group of cells working together for a common function
Cell: most basic unit of life that has all the characteristics of life
Two main purposes for cell division
Growth and repair
Homologous chromosome pair before/after S phase
Interphase
Growth phase
Gap 1, Synthesis, Gap 2
Gap 1
cell grows and makes proteins
Synthesis
DNA replication occurs, doubling chromosomes
Gap 2
more cell growth and protein synthesis
Mitosis
Division phase
Prophase, metaphase, anaphase, telophase
Prophase
chromosomes condense & are visible as sister chromatids (Xs), nuclear membrane disappears, spindle fibers form out of centrioles
Metaphase
spindle fibers connect to the centromeres, chromosomes line up in the middle of the cell
Anaphase
sister chromatids separate and become individual chromosomes, chromatids move to opposite ends of the cell
Telophase
chromosomes decondense and start to look like chromatin again, nuclear membrane reforms, spindle fibers break down, cytokinesis begins
Cytokinesis
division of cytoplasm into 2 individual cells
Cytokinesis in plants vs animals
Plant cells: cell plate forms midway between divided nuclei and gradually develops into a membrane
Animal cells: forms a cleavage furrow that pinches the cell into 2 equal parts
How do cells know when they need to divide?
Cell cycle is controlled by a chemical control system that starts and stops
Internal regulation
signals that come from the cell’s own nucleus (DNA inside of the cell)
External regulation
signals that come from outside of the cell (Hormones, nutrients etc)
Role of checkpoints
critical point where stop and go signals can regulate the cycle
Role of apoptosis
internal/external signals activate genes that produce self-destructive enzymes (ex: web fingers/toes)
Define tumors
clumps of cells that divide uncontrollably
Benign tumor
abnormal cells that typically remain clustered together, may be harmless and easily removed
Malignant tumor
cancer cells that break away from the tumor and move to other parts of the body
List causes of cancer
Biological factors (age, skin type etc)
Lifestyle choices (diet, exposure to UV radiation etc)
Viruses and other infections (HPV)
Exposure to carcinogens (tobacco, asbestos etc)
Differentiation
a process that creates special structures and functions
Stem cells
undifferentiated cells that become differentiated into one or more types of specialized cells
Cell cycle
a repeated pattern of growth, DNA duplication and cell division that occurs in eukaryotic cells
Chromosome
one long continuous thread of DNA that consists of thousands of genes and regulatory information
Gene
a section of DNA with the instructions for making a protein
Sister chromatids
two identical chromatids
Centromere
region of the condensed chromosomes that looks pinched
Telomere
ends of the DNA molecule
Cancer
uncontrolled cell division
Metastasize
spreading of disease from one organ to others
Carcinogens
cancer causing agents; chemicals that cause cancer by mutating DNA