ú  very long (millions of base pairs) double strand of nucleotides

combo of one strand of DNA and many support proteins

ú  small sections of DNA with discrete instructions

physical location of a gene on a strand of DNA (“its address”)

genes are found on DNA, which is found in chromosomes!

·      Contain 2 additional structures:

o   2 telomeres (one on each end)

§  Prevent “fraying” and linking of chrom

o   1 centromere “middle body”

§  Connection point for the two copies of a chrom. Following DNA replication

·      Each copy= sister chromatid

·      There are 23 different chrom.

o   22 autosomes, 1 sex chromosome

·      Autosomes are numbered 1-22 (largest to smallest)

o   1(biggest) contains ~ 3000 genes

o   22 (smallest) ~ 600 genes

o   The 23^rd chrom. Are called X and Y (not 23)

·      All cells (except gametes) have 2 sets/copies of each of the 23 chrom.

·      One set of 23 from mom (egg), one set of 23 from dad (sperm)

o   Diploid (2n)- so 46 chrom. In human cells

·      Gametes are cells that have 1 set/copy of each of the 23 chrom. (eggs/sperm)

o   Haploid (1n or n)

·      During fertilization, egg and sperm chrom. Combine to make a diploid cell (n + n = 2n)

o   “Fertilized egg” is diploid

·      Most other organisms don’t have 23 chrom.

·      When a cell divides, copies of all 46 chrom must be made

o   After division- cell briefly has 92 chromosomes

o   46 pairs of sister chromatids

·      Then, 1 set of 46 ends up in each new daughter cell

·      MITOSIS!!

·      Process by which a diploid cell divides into 2 identical daughter cells (also diploid) 

·      Each daughter cell receives:

o   One copy of each chromosome (46)

o   Roughly 50% of cytoplasm (and organelles)

·      The actual cell division process of divided up into distinct phases

·      Meiosis- only every used to make gametes

·      Start with one diploid cell (2n=46)

·      Replicate all 46 chom

o   46 sister chromatid pairs

·      Cell divides once then again (1 à 2 à 4)

·      Each of the 4 daughter cells contains 23 chromosomes

o   Haploid =n

• In cloning, the chromosomes are removed from the nucleus of a donor egg
• One diploid set of chromosomes from a normal cell is injected into the egg
• Egg is now diploid, carries only chromosomes from the doner cell (it’s a genetic clone of doner)
• Creating excact copy 

• A cell cycle is a cell’s “life”
• Divided into phases
• Most or all of its time is spent in interphase
• If cell divides, it will also spend some time in cell division phase (mitosis)

• Newly created cells begin interphase in G₁
• Growth phase 1
• Cell grows, matures, and division to divide or not is made

• If cell will not divide
• It remains in G₁
• Alive and active
• But no mitosis

• Nerve, muscle, eye cells (e.g)

• If cell is given signal to divide
• It moves into S phase
• Synthesis phase
• DNA/chromosomes are replicated

• After S phase
• Cell moves into final phase
• Final growth & preparation for cell division

• Occurs after g2
• 2 new daughter cells will begin life in G1 phase

Eye

• G₁-S check point- Is the DNA suitable for replication?
• G_2-S- mitosis checkpoint- Has all DNA been completely and accurately copied?
• During Mitosis- Are chromosomes aligned so that distribution to daughter cells is even?

• Programmed cell death (faulty cell)
• Cell sucide
• Used in Cell’s DNA is damaged beyond repair
• Used in normal embryonic development
• Used if cell malfunctions is old and needs to be replaced, is infected with a virus. (ect.)

• Cancer is uncontrolled cell division
• Due to DNA mutations that cause cell cycle regulation to fail
• Usually requires multiple mutations to overcome multiple checkpoints in cell cycle regulation

• 1 – Proto-oncogenes mutate to oncogenes
• Oncogenes constantly promote cell division
• (gas pedal stuck to the floor)
• AND
• 2 – Tumor suppressor genes (TSGs) inactivated
• TSG should stop cell division, but mutation inactivates them
• (emergency brake is broken)
• Seems unlikely that a single cell would have multiple mutations right at these sets of genes

• Billions of cells dividing in our bodies every day, and mutations do occur (natural and external causes)

• •Environmental factors that damage DNA and can lead to cancer forming mutations
• Some viruses
• Some chemicals
• Asbestos, pesticides, etc.
• Tobacco smoke (30% of deaths)
• Radiation (x-rays, UV lights)
• pathway to cancer

• Cells divide quickly and form a large mass
• Tumor
• Benign tumor is a large, but normal, mass of cells that is stationary
• Can be surgically removed
• Only dangerous if it damages healthy tissue around it

• Sometimes cells in a tumor change form
• No longer look / act like normal cell type it was (abnormal)
• Dysplasia
• Dysplasic cells grow into a mass that is called a malignant tumor – considered to be cancer
• These cells can break off and move (via blood or lymphatic system)

grow into a mass that is called a malignant tumor – considered to be cancer

• Moving cells invade other parts of the body and begin new masses
• Metastasis

• mutations in one cancerous cell are passed during cell division, all daughters have them
• Cells are "self" cells hard for immine system to protect
• chemicals target cell in mitosis
• side affects cells rapidly killed
• radiation kills specific areas of cell