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You all started as a single cell, but now your body has
about 100 trillion cells. Where did all of those new cells
come from? Include a drawing in your answer.
http://www.mathsisfun.com/numbers/images/sunflower.jpg http://i-cdn.apartmenttherapy.com/uimages/kitchen/2008_09_04-fruitfly2.jpg
http://preview.turbosquid.com/Preview/Content_2010_12_03__11_39_30/ecoli06.jpg
What do you have in common with these?
E. coli
Sunflower Fruit Fly
you
STRUCTURE OF DNA
• Double stranded helix
• Structure determined in 1953
by Rosalind Franklin, James
Watson and Francis Crick.
• Composed of nucleotides.
DNA is in all living things
DNA is instructions for a cell.
DNA is organized into chromosomes.
Each chromosome has different information.
We have 23 pairs of chromosomes - 1 copy
from dad and 1 from mom.
http://www.biotechnologyonline.gov.au/popups/img_karyotype.html
DNA is in all living things
DNA is instructions for a cell.
DNA is organized into chromosomes.
Each chromosome has different information.
We have 23 pairs of chromosomes - 1 copy
from dad and 1 from mom.
What if a cell didn’t have DNA?
http://www.biotechnologyonline.gov.au/popups/img_karyotype.html
DNA is in all living things
DNA is instructions for a cell.
DNA is organized into chromosomes.
Each chromosome has different information.
We have 23 pairs of chromosomes - 1 copy
from dad and 1 from mom.
NUCLEOTIDESREPEATING UNITS COMPOSED OF:
• Deoxyribose sugar
• Phosphate group
• Nitrogen base
• Adenine
• Thymine
• Cytosine
• Guanine
}
} pair
pair
NUCLEOTIDES CONTINUED ...
• Sugar-Phosphate Backbone
• Weak hydrogen bonds hold
nitrogen bases together
• Sequence of nucleotides
determines genotype of
organism.
Cell division and DNA
cytoplasm
nucleus
cytoplasm
nucleus
cytoplasm
nucleus
sequence images of cell division
Cell division and DNA
Before a cell divides, it has to copy its DNA.
This way, each new cell gets a complete copy of DNA.
cytoplasm
nucleus
cytoplasm
nucleus
cytoplasm
nucleus
DNA REPLICATION
• Enzyme breaks hydrogen bonds
that hold the nucleotides
together DNA unzips.
• Free nucleotides pair with
exposed nucleotides on both
strands.
ANIMATION
• http://www.stolaf.edu/people/giannini/biological%
20anamations.html
nuclear envelope
chromatin
chromatin: loose DNA (looks like noodles)
Interphase - Preparing for cell division
nuclear envelope
chromatin chromosomes
chromatin
condenses
chromatin condenses into chromosomes (DNA is compacted)
Interphase - Preparing for cell division
homologous chromosomes
chromosomes
nuclear envelope
chromatin
chromatin
condenses
Interphase - Preparing for cell division
homologous chromosomes
chromosomes
nuclear envelope
chromatin
chromatin
condenses
homologous chromosomes: 2
chromosomes with similar DNA
(1 from dad, 1 from mom)
Interphase - Preparing for cell division
homologous chromosomes
chromosomes
nuclear envelope
chromatin
chromatin
condenses
chromosomes
get copied
Interphase - Preparing for cell division
homologous chromosomes
chromosomes
nuclear envelope
chromatin
chromatin
condenses
chromosomes
get copied
Interphase - Preparing for cell division
homologous chromosomessister
chromatids
nuclear envelope
chromatin
chromatin
condenses
chromosomes
get copied
chromosomes
sister chromatids: 2 IDENTICAL copies of a chromosome are made when DNA replicates
Interphase - Preparing for cell division
homologous chromosomes
centromerenuclear envelope
chromatin
chromatin
condenses
chromosomes
get copied
chromosomessister
chromatids
Interphase - Preparing for cell division
homologous chromosomes
centromerenuclear envelope
chromatin
chromatin
condenses
chromosomes
get copied
chromosomessister
chromatids
Ready to divide!
Interphase - Preparing for cell division
Prophase
Cell Division (mitosis)
homologous chromosomes
centromerenuclear envelope
chromatin
chromatin
condenses
chromosomes
get copied
chromosomessister
chromatids
Prophase
Cell Division (mitosis)
homologous chromosomes
centromerenuclear envelope
chromatin
chromatin
condenses
chromosomes
get copied
chromosomessister
chromatids
spindle
Prophase
Cell Division (mitosis)
homologous chromosomes
centromerenuclear envelope
chromatin
chromatin
condenses
chromosomes
get copied
chromosomessister
chromatids
spindle
Nuclear envelope breaks down.
Spindle starts to attach to sister chromatids.
Prophase Metaphase
Cell Division (mitosis)
homologous chromosomes
centromerenuclear envelope
chromatin
chromatin
condenses
chromosomes
get copied
chromosomessister
chromatids
spindle
Prophase Metaphase
Cell Division (mitosis)
homologous chromosomes
centromerenuclear envelope
chromatin
chromatin
condenses
chromosomes
get copied
chromosomessister
chromatids
spindle
Sister chromatids line up in the middle of the cell.
Prophase Metaphase Anaphase
Cell Division (mitosis)
homologous chromosomes
centromerenuclear envelope
chromatin
chromatin
condenses
chromosomes
get copied
chromosomessister
chromatids
spindle
Prophase Metaphase Anaphase
Cell Division (mitosis)
homologous chromosomes
centromerenuclear envelope
chromatin
chromatin
condenses
chromosomes
get copied
chromosomessister
chromatids
spindle
Sister chromatids are pulled apart.
Prophase Metaphase Anaphase Telophase
Cell Division (mitosis)
homologous chromosomes
centromerenuclear envelope
chromatin
chromatin
condenses
chromosomes
get copied
chromosomessister
chromatids
spindle
Prophase Metaphase Anaphase Telophase
Cell Division (mitosis)
homologous chromosomes
centromerenuclear envelope
chromatin
chromatin
condenses
chromosomes
get copied
chromosomessister
chromatids
spindle
2 NEs form around 2 sets of chromosomes.
cytoplasm
nucleus
cytoplasm
nucleus
cytoplasm
nucleus
MITOSIS PRODUCES 2
CLONES IN ASEXUAL
REPRODUCTION.
4 chromosomes
4 chromosomes
4 chromosomes
mitosis videohttp://jcb.rupress.org/content/176/6/757/suppl/DC1
Why is mitosis important?
Mitosis is how you grew (from 1 cell).
Mitosis is how your cells are maintained.
Mitosis is how some organisms regenerate body parts.
Mitosis is how single-celled organisms reproduce – ASEXUAL REPRODUCTION.
ASEXUAL REPRODUCTION
• Mitosis is used to produce a NEW organism from part of
ONE other organism.
• DNA in new organism is IDENTICAL to DNA parent
(clone)
ASEXUAL REPRODUCTION
• Types:
1. Fragmentation
2. Budding
3. Parthenogenesis
4. Regeneration
5. Cloning
FRAGMENTATION
• Parent breaks into
several pieces, which
become new organisms.
• Ex. Some worms,
mushrooms, and plants.
BUDDING
• Offspring develop as a growth (bud) on the body of the
parent.
• Ex. Jellyfish, yeast, corals, tapeworms.
PARTHENOGENESIS
• “Virgin birth”
• Female produces eggs that develop into a new organism
without being fertilized.
• Ex. Some species of fish, insects, lizards and frogs.
CLONING
• Making copies of organisms.
• New organism receives DNA from one parent.
• Offspring are genetically identical to parents.
When might mitosis be a bad thing?
Cancer
Cancer is really several diseases.
Cancer occurs when cells that should not divide do divide.
Cancer cells continue dividing, which can lead to a tumor.
Cancer cells can invade other tissues - METASTISIS
When might mitosis be a bad thing?
http://ed.ted.com/lessons/how-do-cancer-cells-behave-differently-from-healthy-ones-george-zaidan
How do cancer cells behave
differently from healthy ones? -
George Zaidan
INVESTIGATING CANCER
• http://media.hhmi.org/biointeractive/click/cellcycl
e/ - cell cycle and cancer
• Metastis - http://www.hhmi.org/biointeractive/vegf
• http://www.hhmi.org/biointeractive/angiogenesis
• What would happen if mitosis was used for sexual
reproduction?
46 chromosomes 46 chromosomes 92 chromosomes
Meiosis 1
Meiosis II
Prophase IMetaphase I
Anaphase I Telophase I
Prophase I1 Metaphase 1I Anaphase 1I Telophase 1I
nuclear envelope
chromatin chromosomes
chromatin
condenses
chromatin condenses into chromosomes (DNA is compacted)
Interphase - Preparing for cell division
homologous chromosomes
chromosomes
nuclear envelope
chromatin
chromatin
condenses
homologous chromosomes: 2
chromosomes with similar DNA
(1 from dad, 1 from mom)
Interphase - Preparing for cell division
homologous chromosomessister
chromatids
nuclear envelope
chromatin
chromatin
condenses
chromosomes
get copied
chromosomes
sister chromatids: 2 IDENTICAL copies of a chromosome are made when DNA replicates
Interphase - Preparing for cell division
homologous chromosomes
centromerenuclear envelope
chromatin
chromatin
condenses
chromosomes
get copied
chromosomessister
chromatids
Interphase - Preparing for cell division
homologous chromosomes
centromerenuclear envelope
chromatin
chromatin
condenses
chromosomes
get copied
chromosomessister
chromatids
Ready to divide!
Interphase - Preparing for cell division
Prophase 1
homologous chromosomes
centromerenuclear envelope
chromatin
chromatin
condenses
chromosomes
get copied
chromosomessister
chromatids
Meiosis 1
Prophase 1
homologous chromosomes
centromerenuclear envelope
chromatin
chromatin
condenses
chromosomes
get copied
chromosomessister
chromatids
spindle
Meiosis 1
Prophase 1
homologous chromosomes
centromerenuclear envelope
chromatin
chromatin
condenses
chromosomes
get copied
chromosomessister
chromatids
spindle
Nuclear envelope breaks down.
Spindle starts to attach to sister chromatids.
Meiosis 1
Prophase 1 Metaphase 1
homologous chromosomes
centromerenuclear envelope
chromatin
chromatin
condenses
chromosomes
get copied
chromosomessister
chromatids
spindle
Meiosis 1
Prophase 1 Metaphase 1
homologous chromosomes
centromerenuclear envelope
chromatin
chromatin
condenses
chromosomes
get copied
chromosomessister
chromatids
spindle Tetrads (groups of 4) of homologous
chromosomes line up in the middle of
the cell.
Crossing over occurs - sister
chromatids exchange
pieces of DNA
Meiosis 1
Prophase 1 Metaphase 1 Anaphase 1
homologous chromosomes
centromerenuclear envelope
chromatin
chromatin
condenses
chromosomes
get copied
chromosomessister
chromatids
spindle
Meiosis 1
Prophase 1 Metaphase 1 Anaphase 1
homologous chromosomes
centromerenuclear envelope
chromatin
chromatin
condenses
chromosomes
get copied
chromosomessister
chromatids
spindle
Homologous chromosomes
are pulled apart.
Meiosis 1
Prophase 1 Metaphase 1 Anaphase 1 Telophase 1
homologous chromosomes
centromerenuclear envelope
chromatin
chromatin
condenses
chromosomes
get copied
chromosomessister
chromatids
spindle
Meiosis 1
Prophase 1 Metaphase 1 Anaphase 1 Telophase 1
Meiosis 1
homologous chromosomes
centromerenuclear envelope
chromatin
chromatin
condenses
chromosomes
get copied
chromosomessister
chromatids
spindle
2 NEs form around 2 homologous
sets of chromosomes.
Prophase 11 Metaphase 11 Anaphase 11
Telophase 11
4 daughter cells are produced.
Each cell has one copy of each chromosome.
SUMMARY OF MEIOSIS
• One parent cell produces 4 daughter cells.
• Daughter cells = gametes = egg & sperm
• The number of chromosomes in daughter cells is half
of what is in the parent cell.• Diploid - 2 copies of each chromosome
• Haploid - 1 copy of each chromosome
HOW IS THE NUMBER OF CHROMOSOMES
RESTORED?
• FERTILIZATION!!
• gamete + gamete = zygote
• haploid + haploid = diploid
• n + n = 2n
• 23 chromosomes + 23 chromosomes = 46 chromosomes