Ch.8: Cell Division-Mitosis

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Binary Fission
Prokaryotes have a simplistic process than eukaryotes

They only have a single loop of DNA

One parent cell divides in half

It results in two identical daughter cells

This is asexual reproduction
What does binary fission result in?
Two genetically identical daughter cells.
How do eukaryotes cells divide?
Mitosis and Meiosis
Mitosis
Somatic cells only

Daughter cells are identical to the parent cell

No diversity is created; like a photocopy
Meiosis
Gametes only

Used for sexual reproduction

Diversity is generated

Chromosome number is reduced in half
Diploid Cells
They have two copies of each chromosome

Cells with a pair of homologous chromosomes
Human Adults
23 chromosome pairs
46 chromosomes total
Haploid Cells
They have one copy of each chromosome.

Cells with only a single copy of a chromosome.
Homologous Pair
Two matching chromosomes from mom and dad with the same sequence of genes.
Chromatid
A single copy of a chromosome
Chromosomes can be:
Unreplicated or Replicated
Sister Chromatid
A chromsome and its identical duplicated version held together at a centromere.
What do cells have to do before dividing?
They have to replicate all of the chromosomes in the cell
DNA
Made up of nucleotides

A double helix is two strands of DNA bound together by hydrogen bonds

Complementary base pairing rules:

A goes with T, C goes with G
Semiconservative Replication of DNA
Unwinding of double helix
The enzyme helices unwinds the DNA double helix

Rebuilding
The hydrogen bonds are broken, allowing the two strands to separate
Each strand serves as a template to make a new strand
DNA polymerase does that
Mitosis
Used for growth, replacement, apoptosis (programmed cell death).
What cells don't do mitosis?
Gametes-Meiosis
Mature muscle cells
Mature nerve cells
Why is mitosis highly regulated?
We don't want to make more cells than we need.
What is cancer?
The unregulated continuation of mitosis.
What is interphase?
G1, S, G2
What is G0?
Sometimes after G1 is a resting phase with no cell division
G1
The cell's primary phase. Normal cellular functions (making proteins, getting rid of waste, etc...) take place.
Synthesis
The cell begins preparation for division. Every chromosome creates an exact duplicate of itself.
G2
Second period of growth and preparation for cell division.
Mitosis
The cell's nucleus duplicates then divides.
Cytokinesis
The cell duplicates and forms two separate cells.
What are the four phases of mitosis?
Prophase, Metaphase, Anaphase, and Telophase.
Apoptosis
Normal cells do not live forever

Programmed cell death

Each time it divides, an average cell loses 30 to 200 base pairs from the ends of its chromosomes (telomeres)

Cells normally can divide only about 50 to 70 times, with telomeres getting progressively shorter until the cells become senescent or die.
Prophase
Chromosomes are fully coiled and condensed

They are in replicated form

The nuclear membrane starts breaking down

Spindle fibers start to form

Four replicated chromosomes
Metaphase
Chromosomes align down the center of the cell

The spindle fibers assist

The order in which chromosomes line up isn't important

Four replicated chromosomes
Anaphase
The spindle fibers pull from each side

The sister chromatids are pulled apart

8 unreplicated chromosomes
The chromosome number has temporarily doubled
Four will be in each daughter cell
Telophase and Cytokinesis
The chromosomes are now divided up

Nuclear membranes need to reform

Cytokinesis must occur

End Result:
Two daughter cells
Four unreplicated chromosomes
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