DNA Replication, Cell Cycle, Mitosis

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DNA Replication

structure of DNA implies replication -->
- antiparallel
-base pair bonding
-H+ bonds

Semiconservative

1/2 old and 1/2 new
Daughter strand --> 1 parent DNA and 1 new DNA

Conservative

Original is original. Copies are copies. NOT way DNA is replicated.

DNA Replication

Bases are added sequentially
Daughter DNA is identical to parental DNA

Enzymes Specific Jobs

topoisomerase/helicase --> unwinding, straightening DNA out
primase --> primes the site, starts the process
polymerase --> lays down nucleotides
ligase --> glues the ends together

Leading and Lagging Strand

DNA is stable as double strand
Once DNA is opened, become fragile so binding proteins bind to strand making it stable
Leading --> 1 continuous strand
Lagging --> pieces of DNA glued together

Functions of Cell Division

-reproduction
-growth and development
-tissue renewal

Cell Cycle -Interphase

G1 Phase - growth -->adding pieces
S Phase - DNA synthesis --> takes about 7 hours
G2 Phase - growth --> adding pieces

Mitosis

-small portion of cycle
-occurs after growth and synthesis
-division of nucleus

Chromosomes

-complete structure

Chromatid

-sister
-single copy of duplicated DNA (attached)

Chromatin

-all of the nuclear material

Centromere

-where sister chromatids are attached
-where spindle fibers attach during mitosis

Centrosome

-organize spindle fibers

Mitosis

-division of nucleus
- 5 phases --> prophase, prometaphase, metaphase, anaphase, and telophase

Prophase

- 1st phase --> visibility phase
- condensation of chromosomes
-centrosomes appear and migrate
-spindle fibers appear

Prometaphase

-breakdown of nuclear membrane
-spindle fibers attach to centromeres

Metaphase

- chromosomes pair up
- chromosomes align randomly on plate/center
-spindle fibers visible

Anaphase

- centromeres divide
-sister chromatids move to opposite poles

Telophase

-nuclear membrane reforms
-chromosomes uncondense
-spindle fibers disappear
- cell division begins

Cancer

-cells divide out of control
-"checkpoints" during each phases of the cell cycle
- cells ignore checkpoints

Tumors

-Benign --> slow growing and harmless (warts and moles)
-Malignant --> invades adjacent tissue (metastasizes)

Differences of Cancer Cells and Normal Cells

- cancer cells divide uncontrollably
- immortal --> normal cells die after about 50 cycles, cancer cells can survive 100's-1000's cycles; telomerase --> there for protection, munched on like RNA tail so after about 50 cycles it's gone and good DNA is munched on
-various growth factors
-lack contact inhibition -->lack control and push other cells out of the way so that's why you get lump

Causes of Cancer

-environment (UV light, chemicals, etc.)
-viruses
-most causes can be eliminated through education

Risk Factors of Cancer

-tobacco use
-obesity
-lack of exercise
-UV exposure
-poor diet
-virus exposure

Treatments for Cancer

-killing abnormal cells with either chemotherapy or radiation therapy
-removing abnormal cells through surgery

Apoptosis

-programmed cell death
-human approx. 50 cycles
-aging or defective cells
-also in development --> create spaces for fingers and toes

Helicase

- enzyme that unwinds the DNA in preparation of replication

Binding Proteins

-Stabilize each strand because DNA becomes very fragile when opened up

Primase

- enzyme that add short RNA primer to template strand

DNA Polymerase

- enzyme that binds nucleotides to form new strands
-proofreads as it goes along

Ligase

- joins Okazaki fragments and seals the nicks in sugar-phosphate backbone

Okazaki Fragments

- short pieces of DNA from the lagging strand

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