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Chromosomes and Cell
Reproduction
Section 1
Chromosomes
Section 2
Cell Cycle
Section 3
Mitosis
3 Types of Cell Division
• Prokaryotic Cells (bacteria) undergo
reproduction by dividing (asexual reprod.)
• Eukaryotic Cells undergo growth, repair,
development by mitosis
• Meiosis is the formation of gametes, which are
the organisms’ reproductive cells (eggs/sperm)
• *** Each cell ends up with a complete set (copy)
of DNA
Prokaryotic Cell Reproduction
• No NUCLEUS
• DNA is circular ad
attached to the inner cell
membrane.
• Binary fission-form of
asexual reproduction
that produces identical
offspring
Eukaryotic Cell Reproduction
• Most information encoded
in DNA is organized into
genes
• Genes are segments of
DNA that code for a
protein or RNA molecule
• Chromosomes are coiled
structures of DNA
• DNA is copied (2
chromatids) and each
new cell gets one
chromatid.
DNA, Chromosomes, Genes
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Chromosome Number
• Each human somatic cell contains 23 pairs of
chromosomes (total of 46)
• Each chromosome contains thousands of genes
that determine how a person develops
• Homologous chromosomes are chromosomes
that are similar in shape, size, and genetic
content
• One set of chromosomes from each (mom/dad)
Somatic Cells vs. Gametes
• Body cells (somatic) are
diploid, which means they
contain 2 sets of
chromosomes
• Gametes (sperm/egg)
are haploid - 1 set.
• N = 23
2N = 46
• Fertilization - fusion of 2
haploid gametes
• Zygote - fertilized egg
cell
Fertilization/Meiosis
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Sex Chromosomes
• Autosomes - (1-22)
chromosomes that are
not involved with
determining gender
• Sex Chromosomes- 1
chromosome out of 23
determines gender
• XX or XY
• 23rd Chromosome
Change in Chromosome #
• Down’s Syndrome Trisomy 21 (3 copies of
the 21st chromo.)
• Karyotype - a photo of
chromosomes that sorts
them by size
• Non-disjunction if one of
more chromosomes fail to
separate properly
Mutation - A Mistake
•
•
•
•
•
Mutation- change in chromosome structure
Deletion mutation - piece breaks off
Duplication mutation - 2 copies of genes
Inversion mutation - reverse order of genes
Translocation mutation - piece of chromosome
attaches to a non-homologous chromosome
The Cell Cycle
• Cell cycle is a repeating sequence of cellular
growth and division
• Interphase- 1st three phases of the cycle (cell
spends 90% of time here)
• 1st (G1) = first growth phase
• 2nd (S) = synthesis phase (DNA copied)
• 3rd (G2) = second growth phase
• 4th (mitosis) = process of cell division
• 5th (cytokinesis) = cytoplasm divides in half
Cell Cycle Continued
• Proteins control cell
cycle (tell when to divide)
• Cancer - uncontrolled
growth of cells or
disorder of cell division
• Either produce growthpromoting molecules or
inactivate control
proteins.
Mitosis and Cytokinesis
• During mitosis the nucleus divides, each
containing a complete set of chromosomes
• Chromatids on each chromosome are physically
moved to opposite sides of the dividing cell with
the help of the spindle.
• Spindles are cell structures made up of
centrioles and microtubule fibers that are
involved in moving chomo. In cell division
Stages of Mitosis
• 1= Prophase - chromosomes coil up
• 2= Metaphase - chromosomes move to center of
cell and line up on equator
• 3=Anaphase - centromeres divide and
chromatids move toward opposite poles
• 4=Telophase - nuclear envelope forms around
chromosomes at each pole
• Cytokinesis - cytoplasm divides in half
Mitosis
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Sorenson Video 3 decompressor
are needed to see this picture.
Mitosis Animation
http://www.loci.wisc.edu/outreach/bioclips/CDBio.html
http://nobelprize.org/educational_games/medicine/2001/cellcycle.html