moving materials in and out transport within the cell communication to and from nucleus surface...
TRANSCRIPT
Cellular DivisionMitosis, Meiosis, and More!
Why do cells divide?
Why divide?
Moving materials in and out
Transport within the cell
Communication to and from nucleus
Surface area to volume ratio decreases as a cell grows
DNA “Overload”
Chromosomes
Tightly wound DNA around HISTONE proteins› Appears like
“beads-on-a-string”
Key words:› Chromatids› Sister Chromatids› Centromeres› Homologous Pair
The “Super-coil”!
The Chromosomes that we commonly see are the results of multiple sections where the DNA is wrapped around resulting in a “SUPER-COIL!”
This is a homologous pair. One of these is from the mother while the other is inherited from the father. They contain the same type of genes (like hair color) but different specific information (like blonde or brown).
Where is the centromere?
What is a sister chromatid?› Where are they?
Wh
at ty
pe o
f plo
ids?
Haplo
idD
iplo
id
Having ONE set of chromtid chromosomes
Exists in Sperm and Egg cells (Sex Cells or Gametes)
Humans: 23 Chromosomes
Having TWO sets of chromatid chromosomes
Exists in the somatic cells (Body cells other than gametes)
Humans: 46 Chromosomes
Birds and the Bees
Gamete: Sex Cells› Haploid
Male= Sperm
Female= Egg
Zygote: Fertilized Egg› Diploid
Sperms unites with an Egg
The Cell Cycle: Mitosis
This is the process referred to as cell division
One Cell divides into two similar/identical cells
Why?
Growth and Repair
G1
• Gap 1• Growth
and Function
S
• Synthesis of DNA
• DNA copied into Sister Chromatids
G2
• Organelles replicate
• Mitotic Spindles form
M
• Mitosis• Nuclear
Division• 2 Identical
Cells
C
• Cytokinesis
• Cytoplasm division
After Cytokinesis (C), The process begins over again
***90% of the cells life is spent in G1, S, and G2***
M is for Mitosis…
Interphase – G1, S, G2
Chromatin, cell function, DNA
Replication
Prophase• Nucleus disappears• Chromatin chromosomes• Centrioles move to opposite poles
Metaphase• Sister chromatids line up in middle
• Middle is called equatorial plane
• Spindle fibers connect to chromosomes
Anaphase• Centromeres split• Sis. chromatids are pulled apart• Spindle fibers contract
Telophase• New nucleus forms• Chromosomes Chromatin• Cytokinesis
Video of Mitosis
***IMPORTANT****
1. Make sure that you can recognize pictures of each one of these phases and say them by name
2. Also be able to use a microscope to find each one of these phases
Meiosis: Reduction Division
The purpose is to produce haploid gametes (sex cells)
The cell divides twice
4 cells that are not identical, but have the correct # of chromosomes
Important because it causes differentiation and maintains chromosome # in zygote
Overview of Meiosis
Meiosis I: Homologous chromosomes separate into 2 diploid cells. Similar to Mitosis.
Meiosis II: 2 diploids become 4 haploid cells.
Meiosis - IPMATPMAT
1 IPMAT
Homologous pairs divide
During Metaphase-1 crossing over
occurs
2 PMAT
Sister chromatids divide creating haploid gametes
So W
hat’s
the
Diff
ere
nce?
Mito
sisM
eio
sis
Somatic cells (Body)
2 identical daughter cells
Maintains Chromosome #› Diploid
Divide once
Gametes (Sex)
4 different daughter cells
Reduce Chromosome #› Haploid
Divide twice
Advantages and Disadvantages
Sexual
Diversity
Genetic Recombination
Few Offspring
Requires tons of Energy
Asexual
Lots of Offspring
Don’t need anyone else
Little Evolution
Limited Environment
Cancer: Run-away Mitosis
Causes: Numerous different theories
› All result in mutations that cause oncogenes to be turned on and tumor suppressor genes to be turned off.
› This messes up your DNA.
› Oncogenes- Stimulate growth AKA Cell division.› Tumor suppressor genes- restrain cells’
ability to divide.
How Cancer works…
1. Initiation- a mutation occurs to usually 1 (or more) genes. Time to next stage= 20-25 years.
2. Promotion- Anything that happens that leads to expression of the mutation.
› Ex: Cells dividing too quickly.
3. Progression- tumor grows larger and larger, tumor produces enzymes and proteins that direct blood to tumor.
4. Metastasis- Cancer spreads to other parts of the body.
The Diabolical Superpowers of Cancer
6 common characteristics to all cancers
1. Growth w/out a go signal2. Growth even against stop signals3. Evades autodestruct signals4. Ability to stimulate blood vessel
construction5. Immortality6. Metastasis- Ability to spread to new
tissue.
Cancer Treatments
Surgery: Try to cut out the cancer Radiation: Attempt to kill off all rapidly
dividing cells Chemotherapy: Targets all dividing cells
Essentially all versions work to kill the cancer cells
Not all Sunshine… (Drawbacks)
Drawbacks: Illness › Radiation- can’t pinpoint cancer cells. › Chemo- targets all dividing cells. (Hair falls out, blood
production decreases)› Surgery- may not get all cells.
However… There is a light at the end of the tunnel
RNAi: A special type of RNA that can turn off Oncogenes without drawbacks› POTENTIALLY A PERFECT CURE!!!!!
Embryonic and Fetal Development
• Cleavage – results in a hallow ball of cells called *blastocystWeek
1• Gastrulation – Formation of 3 primary tissue
types: endoderm, mesoderm, and ectodermWeek2
• Neurulation – Formation of dorsal hollow nerve chord
• Blood vessels begin to formWeek
3• Organogenesis – organs form• Heart beats• Limb buds form
Week4
Fetal Development Continued…
• See previous 2 slides• 1-3 months1st
Trimester• 4-6 months• Morphogenesis – limbs assume adult shape• Organs grow and fully develop2nd
Trimester• 7-9 months• Lungs develop last• Growth – fetus can survive if born during this stage3rd
Trimester
