Cell Cycle and Mitosis
Cell Cycle and MitosisCell Division — process by which a cell divides into 2 new cells
Parent Cell
2 Daughter Cells
Parent Cell
2 Daughter Cells
•The original cell is called the parent cell; 2 new cells are called daughter cells
Why do cells need to divide?
● Living things grow by producing more cells, NOT because each cell increases in size
● Repair of damaged tissue
● If cell gets too big, it cannot get enough nutrients into the cell and wastes out of the cell
Do you remember?1) Which cell organelle controls all cell
functions?
2) What does this cell organelle contain?
3) What do ALL cells need in order to have the directions/code to perform functions correctly?
Nucleus
Genetic Information
DNA
DNA•DNA is located in the nucleus and controls all cell activities including cell division•Long and thread-like DNA in a non-dividing cell is called chromatin•Doubled, coiled, short DNA in a dividing cell is called chromosome
Consists of 2 parts: chromatid and centromere
Compare and Illustrate DNADNA in NON-DIVIDING Cell DNA in a DIVIDING Cell
Chromatin
Duplicates itself
Coils up into chromosomes
•Chromatin to chromosomes illustration:
Why does DNA need to change from chromatin to chromosome? More efficient division
o2 identical “sister” chromatids attached at an area in the middle called a centromere
oWhen cells divide, “sister” chromatids separate and 1 goes to each new cell
•Before cell division occurs , the cell replicates (copies) all of its DNA, so each daughter cell gets complete set of genetic information from parent cell•Each daughter cell is exactly like the parent cell – same kind and number of chromosomes as the original cell
Cell Cycle and Mitosis
•Every organism has its own specific number of chromosomes Examples: Human = 46 chromosomes or 23 pairs Dog = 78 chromosomes or 39 pairs Goldfish = 94 chromosomes or 47 pairs Lettuce = 18 chromosomes or 9 pairs
•All somatic (body) cells in an organism have the same kind and number of chromosomes. Examples: Human = 46 chromosomes Human skin cell = 46 chromosomes Human heart cell = 46 chromosomes Human muscle cell = 46 chromosomes
Fruit fly = 8 chromosomesFruit fly skin cell = 8 chromosomesFruit fly heart cell = 8 chromosomesFruit fly muscle cell = 8 chromosomes
Cell Cycle -- series of events cells go through as they grow and divide•Cell grows, prepares for division, then divides to form 2 daughter cells – each of which then begins the cycle again
Cell Cycle Outline● Interphase
G1: Cell Grows S: DNA Replicates G2: Growth &
prepares for division
• Mitosis Prophase Metaphase Anaphase Telophase
• Cytokinesis
Cell Cycle and Mitosis
● Interphase● Prophase● Metaphase● Anaphase● Telophase● Cytokinesis
Get a friend and create a sentence to help you
remember the order of the cell cycle and mitosis. Use
the first letter of each term.
Interphase
● Interesting things happen!
1. Cell preparing to divide
2. Genetic material doubles
3. Cells most of their time in Interphase
•Mitosis – division of the nucleus into 2 nuclei, each with the same number of chromosomes•Mitosis occurs in all the somatic (body) cells
Mitosis BeginsProphase, Metaphase, Anaphase, Telephase
Prophase● Chromosome pair
up!
● Chromosomes become visible
● Nuclear membrane disappears
● Spindle fibers form
Prophase
Metaphase
● Chromosomes meet in the middle!
● Spindle Fibers connect to chromosomes
Metaphase
Anaphase
● Chromosomes get pulled apart
● Spindle fibers pull chromosomes to opposite sides
Anaphase
Telophase● Now there are
two!● Chromosomes
uncoil● Spindle fibers
disappear● Two nuclei are
formed
Telophase
Cytokinesis — the division of the rest of the cell (cytoplasm and organelles) after the nucleus divides
In animal cells the cytoplasmpinches in
In plant cells a cell plate forms
•After mitosis and cytokinesis, the cell returns to Interphase to continue to grow and perform regular cell activities
Cytokinesis
Mitosis is a type of asexual reproduction.
● There are two types of reproduction:
Asexual Reproduction
Sexual Reproduction
• parent reproduces by itself
• offspring is genetically identical to “mamma”
•Offspring is genetically unique
• creates diversity within population
1) Mitosis 2) Binary Fission3) Budding4) Spores5) Regeneration6) Vegetative Propagation
Asexual Reproduction
produce 2 identical daughter cells with the same # of chromosomes as the parent cell. (identical)
1) Mitosis 2) Binary Fission
• a parent cell splits into 2 daughter cells of = size
• w/ prokaryotes
3) Budding
4) Spores
• a new, duplicate organism forms at the side of the parent and enlarges until an individual is created.
• spores are surrounded by a tough coat to help them survive harsh conditions. .. Produced and released
5) Regeneratio
n
6) Vegetative Propagatio
n
• growth of new tissues/organs to replace those injured or lost.
• Common in invertebrates, especially Asteroidea (Sea Stars) and Annelida (Worms).
* In some multicellular plants * new plants develop from the
roots, stems, or leaves of the parent.
stolons
Sexual Reproduction
1) Meiosis
Cell division that results in haploid gametes; used for sexual reproduction
Haploid?
● When a gamete (sperm or egg) of an organism has HALF of the full amount of chromosomes
● Hap Half● Remember, human
cells have 46 chromosomes? Then the haploid # is 23
Sperm
Egg
Meiosis
Meiosis I● All chromosomes make
copes of themselves● This doubles the # of
chromosomes in the cell
Meiosis II● Begins in same two cells
created by Meiosis I● Creates FOUR new haploid
cells● Occurs in a manner very
similar to mitosis
● Occurs in the same four phases as mitosis but in two steps: Meiosis I and Meiosis II
Outline of Meiosis● Meiosis I
– Prophase I– Metaphase I– Anaphase I– Telophase I
● Meiosis II– Prophase II– Metaphase II– Anaphase II– Telophase II
Prophase I● Homologous
chromosomes from each parent pair up!
● They form two attached sets of chromatids called a tetrad
● There are MANY ways the chromatids can line up: this is one source of genetic variation.
Homologous chromosomes:
•1 from each parent
•carry genes that control the
sameinherited traits.
Metaphase I● Each tetrad meets
in the middle!● Spindle fibers
connect centromeres
● Crossing over of chromosomes may occur to provide additional genetic variation – 2nd source of genetic variation
Anaphase I
● Tetrads get pulled apart
• Homologous chromosomes move to opposite ends
Telophase I● Cells may finish
cytokinesis OR proceed immediately with Meiosis II
Prophase II● Chromosomes did
NOT replicate
● At this point, the cell is haploid because it no longer has one of every kind of chromosome that was in the original cell
Metaphase II● Sister chromatids
line up on individual spindle fibers
Anaphase II
● Sister chromatids are separated into each new cell
● Each new cell now has only HALF as many chromosomes as the parent cell in Prophase I
Telophase II● Each of the four
new cells completes reforming nuclei and cytokinesis separates the four new hapliod cells
How does meiosis lead to genetic variation?
● Look back at Prophase I & Metaphase I, what may lead to genetic variation?– There are MANY ways the chromatids can
line up
– Crossing over of chromosomes may occur
● What is another factor that could lead to genetic variation?– Random combinations of sperm and eggs
Interphase
Prophase 1
Metaphase 1
Anaphase 1
Telophase 1
Mei
osis
1In
terp
hase
Revie
w!
Mei
osis
2C
ytok
ines
is
Prophase 2
Metaphase 2
Anaphase 2
Cytokinesis
Note..Note..Male gametes
Female gametes
4 haploid gametes … 4 sperm by way of spermatogenesis
4 haploid gametes … 1 Ovum (egg) & 3 Polar Bodies by way of oogenesis
Sometimes cell division doesn’t go as planned…
Cell Division Regulation
● Internal and external factors regulate cell division.
● Cancer is the uncontrolled growth and division of cells.
● Cancer cells can kill an organism by crowding out normal cells, resulting in the loss of tissue function.
Cancer ● Benign – cancer cells
typically remain clustered together
● Malignant – cancer cells can break away or metastasize
cancer cellbloodstreamnormal cell
Benign Malignant
metastasize
Causes of Cancer
● Internal Factors
– Inheritance
– Mutations
● External Factors
– Carcinogens are substances that are known to produce and promote the development of cancer.
– Radiation– Chemical– Viruses
Skin Cancer
Nondisjunction Mutations● Improper separation of sister chromatids may
result in a cell having one too many chromosomes (trisomy) or not having one of a certain chromosome (monosomy)
Karyotype – a picture of an individual’s chromosomes so that the types of mutations might be seen
Trisomy 21 – Down Syndrome
Trisomy 18 - Edward's Syndrome
Meiosis Square Dance
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