DNA and Mitosis Notes - jmueller2.weebly.com · Mitosis Notes LISA Pre-AP Biology . DNA ! Stands...
Transcript of DNA and Mitosis Notes - jmueller2.weebly.com · Mitosis Notes LISA Pre-AP Biology . DNA ! Stands...
DNA and Mitosis Notes LISA Pre-AP Biology
DNA � Stands for deoxyribonucleic acid
� DNA is an example of what kind of macromolecule? � Nucleic acids!
� Function � Contains the “code” for life � Is the pattern for making proteins
� **more on this next semester!
� Found in the nucleus � Characteristics
� Double stranded helix � Twisted ladder
� Can take on a few different forms � Chromatin: an
uncondensed form of DNA � The DNA is loose, like an
unraveled extension cord
� Chromosome: a condensed form of DNA � The DNA is organized, like
an extension cord that is all wound up
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� DNA is an example of a nucleic acid polymer What is the monomer called?
� Nucleotide � Nucleotide = base unit
of DNA � Consists of sugar,
phosphate, and a nitrogen base
Nitrogen Base � There are four
� Adenine (A) � Cytosine (C) � Thymine (T) � Guanine (G)
Nitrogen Bases � These bases bond in
very specific ways � Adenine always binds
with Thymine � Cytosine always bonds
with Guanine
� Example: � Given that DNA is a double strand, what is
the code on the mystery strand?
Strand 1: A C T C G A C T G A T C
� Example: � Given that DNA is a double strand, what is
the code on the mystery strand?
Strand 1: A C T C G A C T G A T C
Strand 2: T G A G C T G A C T A G
� When a cell divides, it must be copied. � Known as replication � This is going to make a new copy of DNA for
the new cell
� Next, we are going to talk about how the cell divides and what happens to the DNA
Cell Division � Cell division is necessary for the
reproduction of both somatic (body) and sex cells (gametes) � Division of somatic cells: mitosis � Division of gametes: meiosis
� Involves the distribution of identical genetic material (DNA) to two daughter cells
The Cell Cycle
� Interphase � G1 � S � G2
� Cell Division � Mitosis � Cytokinesis
Cell Division
Cytokinesis
M phase
G1 phase (Cell Growth)
S Phase (DNA Copied)
G2 Phase (Growth and prepara>on
for division)
Interphase
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Interphase � Most of the time spent in this
phase � Cell grows and copies its
chromosomes in preparation for cell division
� G1 = Growth � S = DNA Synthesis
� DNA is copied � G2 = Cell prepares for division
� Sometimes cells exit cycle from G1 and enter G0 where they simply exist and never divide.
Interphase � G1 Phase; “first gap”
� Cell grows by producing proteins and organelles
� S Phase; “synthesis” � Chromosomes are duplicated
� G2 Phase; “second gap” � Cell continues to grow and prepares for
division
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Mitosis � Division of the nucleus � 4 phases of Mitosis
� Prophase � Metaphase � Anaphase � Telophase
Prophase � Chromatin condenses to become chromosomes
� Chromosomes appear as sister chromatids � They are identical!
� Nuclear membrane disappears � Centrioles (an organelle) move to opposite sides
of the cell � creates spindle fibers
� Microtubules
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Metaphase � Chromosomes line up along center of cell
� The “metaphase plate” � Spindle fibers attach to centromere to move them
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Anaphase � Sister chromatids
separate at the centromere � Chromatid: half
of a chromosome
� Slowly pulled to opposite sides of the cell
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Telophase � Two daughter nuclei begin to form � Spindle fibers disassemble � Chromosomes return to chromatin � Nuclear membrane forms � Mitosis is complete
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Cytokinesis � Division of the cytoplasm � Animal cells pinch in creating cleavage furrow � Plant cells develop a cell plate
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