Are we unicellular,
or
multicellular?
How can we get so big if
we start off as 1 cell?
 Cells have to be able to divide
 What needs to be done for a cell to divide?
 DNA has to replicate and divide
 Cytoplasm needs to divide
Vocabulary
Cell Divisions
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Chromatin Chromosome Chromatid Cell cycle Interphase DNA ReplicationReplicationMitosis –
Cytokinesis -
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DNA
 DNA in the shape of a double helix
 DNA is made of
 Deoxyribose as the backbone and 4 types of
nitrogen bases as the rungs of the ladder
Chromatin to Chromosome
 DNA Replication—
Replication—The DNA unzips and new
bases are added making two identical strands of
DNA
The Life of a Cell
 The cell cycle begins when the cell is
formed and ends when the cell divides
and forms new cells.
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Cell Cycle
Phases of the cell cycle
InterphaseInterphase- cell grows and DNA replicates
Prophase—
Prophase—DNA condenses into chromosomes and
nucleus disappears
Metaphase—
Metaphase—Chromosomes line up on equator
Anaphase—
Anaphase—Chromosomes (sister chromatids) separate
Telophase—
Telophase—Nucleus reforms, Chromosomes unwind into
chromatin, cell starts to split
Cytokinesis–
Cytokinesis– cytoplasm splits to form 2 cells
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Mitosis
 Click below to watch the Visual Concept.
Visual Concept
 You may stop the video at any time by pressing
the Esc key.
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 http://www.iknow.net/CDROMs/cell_cdrom/cellmovies.shtml
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Chapter 5
Section 3 Meiosis
Asexual Reproduction
Mitosis animation
Mitosis animation
Mitosis animation freeman
Eukaryotic cell
 http://highered.mcgrawhttp://highered.mcgraw-hill.com/olc/dl/120073/bio14.swf
• In asexual reproduction, only one parent cell is
needed. The structures inside the cell are copied, and
then the parent cell divides, making two exact copies.
• This type of cell reproduction is called mitosis. Most
of the cells in your body and most single-celled
organisms reproduce this way.
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Chapter 5
Section 3 Meiosis
Chapter 5
Section 3 Meiosis
Sexual Reproduction
Sexual Reproduction, continued
• In sexual reproduction, two parent cells (sex cells)
join together to form offspring that are different from
both parents.
• Meiosis Sex cells are made during meiosis.
• Chromosomes that carry the same sets of genes
are called homologous chromosomes.
• Meiosis is a copying process that produces
cells with half the usual number of
chromosomes.
• Each sex cell has only one of the chromosomes
from the homologous pair.
Chapter 5
Section 3 Meiosis
Meiosis
Meiosis
Click below to watch the Visual Concept.
Visual Concept
You may stop the video at any time by pressing
the Esc key.
 Humans have 46 chromosomes or 23 pairs
 ½ from mom and ½ from dad
 Meiosis = cell division that cuts the number of
chromosomes in half and produces sex cells
 4 sex cells are produced each with only half the
number of chromosomes
 Diploid= having 2 sets of chromosomes
 Haploid= having 1 set of chromosomes
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Moms
Dads
Each cell has 2 sets of doublestranded chromosomes
1 from mom and
1 from dad
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Could be either
moms or dads
Each of 2 cells now has only 1 set
of double-stranded chromosomes
The cells are now haploid-1/2 the
number of chromosomes
Each of 4 cells now have only one
strand of each chromosome= sex
cell
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Review
 How many cells does mitosis produce?
 2
 How many chromosomes are in each cell (full or half)?
 Full set – diploid
 How many cells does meiosis produce?
 4
 How many chromosomes are in each cell (full or half)?
 Half the chromosomes – haploid
 Where does mitosis occur?
 Body cells—
cells—everywhere else besides reproductive organs
 Where does meiosis occur?
 Reproductive organs
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  Activity
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