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Biology - Cell Division/Mitosis

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james donahue

on 7 February 2017

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Transcript of Biology - Cell Division/Mitosis

Cell Division
Big Questions:
Make Sure You Can:
Why Divide?
The Cell Cycle
Mitosis
The "continuity of life"
1 - In order to survive, the individual must replace damaged cells.
2 - In order to grow, cell production must be greater than cell death.
In order to survive, the species must replace individuals.
Cell division accomplishes these purposes.
A dividing amoeba
A dividing bone marrow cell
A dividing sea urchin embryo
The phases of a cell's life
G1- growth
S- DNA replication
G2- preparation for division
M - Mitosis

G0- Non-dividing state (most cells in you)
Chromosomes!
Very tightly controlled (why?)
Tightly coiled pieces of DNA that condense prior to division
Remember!
Prokaryotes only have one, circular chromosome.
Most eukaryotic cells have 2 copies of every chromosome.

They form in attached, identical pairs.

Chromatid: 1 member of the pair
Centromere: region where they are joined
Chromatids
Centromere
S phase
Mitosis
Make sure you understand the chromosome, chromatid relationship



It can be confusing...
Haploid vs. Diploid
1 copy of every chromosome (n)
2 copies of every chromosome (2n)
Human cells have 23 pairs of chromosomes

How many chromatids are present during:
G1?
G2?
Interphase
Chromosomes Condense
Nuclear envelope breaks down
mitotic spindle begins to form
Animal cells: centrioles divide.
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
Cytokinesis
Chromosomes begin to migrate to cell equator.
2 complete spindles at cell poles.
Chromosomes are at metaphase plate.
Spindle attaches to "kinetochore" of chromosomes at centromere
Chromatids split apart at centromere.
Migration of chromatids to cell poles mediated by the kinetochore.
Chromosomes decondense
Nuclear envelope reforms
Cytokinesis: cell membrane divides
Growth
Replication of DNA
Preparation for division

Most of a cells life cycle
Newt, Whitefish, Onion
Differences between plant-like and animal-like cells (Why?)
Plants
Animals
A "contractile ring" of microfillaments pinches the cell in 2
Vessicles from both cells deposit a new cell wall partition ("cell plate") in the middle of the cell.
Organelle apportionment is essentially random.
Mitosis at a Glance
Let's play "spot the phases"
"Non-Reductive"
(Xerox copy)
Eukaryotic Cell Division
Describe the roles that mitosis plays in eukaryotic organisms.

Explain how mitosis produces two genetically identical cells

Explain how interphase prepares a cell for mitosis.

Explain why many cells never divide.

Explain the function of each stage of mitosis

Compare the events of mitosis in plant-like and animal-like cells
Why do cells need to divide?

How does cell division provide for continuity of life processes in an individual and in a species?
"Binary Fission"
The splitting of
the cell into two.
www.youtube.com/watch?v=L0k-enzoeOM
www.youtube.com/watch?v=C6KDlTI2884
DNA - Episode 4: Curing Cancer
So, what is CANCER?
www.youtube.com/watch?v=ofjyw7ARP1c
Trisomy 13, also called Patau syndrome, is a chromosomal condition associated with severe intellectual disability and physical abnormalities in many parts of the body. Individuals with trisomy 13 often have heart defects, brain or spinal cord abnormalities, very small or poorly developed eyes, extra fingers or toes, an opening in the lip (a cleft lip) with or without an opening in the roof of the mouth (a cleft palate), and weak muscle tone (hypotonia). Due to the presence of several life-threatening medical problems, many infants with trisomy 13 die within their first days or weeks of life. Only five percent to 10 percent of children with this condition live past their first year.
Trisomy 18, also called Edwards syndrome, is a chromosomal condition associated with abnormalities in many parts of the body. Individuals with trisomy 18 often have slow growth before birth (intrauterine growth retardation) and a low birth weight. Affected individuals may have heart defects and abnormalities of other organs that develop before birth. Other features of trisomy 18 include a small, abnormally shaped head; a small jaw and mouth; and clenched fists with overlapping fingers.


Due to the presence of several life-threatening medical problems, many individuals with trisomy 18 die before birth or within their first month. Five to 10 percent of children with this condition live past their first year, and these children often have severe intellectual disability.
Down syndrome is a chromosomal condition that is associated with intellectual disability, a characteristic facial appearance, and weak muscle tone (hypotonia) in infancy. All affected individuals experience cognitive delays, but the intellectual disability is usually mild to moderate. About half of all affected children are born with a heart defect. Digestive abnormalities, such as a blockage of the intestine, are less common. Individuals with Down syndrome also have an increased risk of hearing and vision problems. Additionally, a small percentage of children with Down syndrome develop cancer of blood-forming cells (leukemia). Speech and language develop later and more slowly than in children without Down syndrome, and speech may be more difficult to understand. Behavioral issues can include attention problems, obsessive/compulsive behavior, and stubbornness or tantrums. People with Down syndrome often experience a gradual decline in thinking ability (cognition) as they age, usually starting around age 50 and are associated with an increased risk of developing Alzheimer disease, a brain disorder that results in a gradual loss of memory, judgment, and ability to function.
Turner syndrome is a chromosomal condition that affects development in females. The most common feature of Turner syndrome is short stature, which becomes evident by about age 5. An early loss of ovarian function is also very common. The ovaries develop normally at first, but egg cells (oocytes) usually die prematurely and most ovarian tissue degenerates before birth. Many affected girls do not undergo puberty unless they receive hormone therapy, and most are unable to conceive (infertile).
Klinefelter syndrome is a chromosomal condition that affects male physical and cognitive development. Its signs and symptoms vary among affected individuals. Individuals typically have small testes that do not produce as much testosterone as usual. A shortage of testosterone can lead to delayed or incomplete puberty, breast enlargement, reduced facial and body hair, and an inability to have biological children (infertility). Some affected individuals also have external genital differences.
47,XYY syndrome is characterized by an extra copy of the Y chromosome in each of a male's cells. Although males with this condition may be taller than average, this chromosomal change typically causes no unusual physical features. Most males with 47,XYY syndrome have normal sexual development and are able to father children. There may be an increased risk of learning disabilities and delayed development of speech and language skills. Delayed development of motor skills, weak muscle tone, hand tremors or other involuntary movements, and behavioral and emotional difficulties are also possible.
Ant - 2
Cabbage - 18
Chicken - 78
Chimpanzee - 48
Human - 46
Tobacco - 48
Donkey - 62
Horse - 64
Mule - 63
Eukaryotes have many,
linear chromosomes
www.youtube.com/watch?v=lpAa4TWjHQ4
www.youtube.com/watch?v=f-ldPgEfAHI
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