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33 terms

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