The Cellular Basis of
Reproduction and Inheritance
Cell Division: The Cell Cycle and Mitosis
The Production of Identical Cells
Meiosis
The Production of Sperm and Eggs
Homologous Chromosomes
Homologue inherited
from dad
Homologue inherited
from mom
This karyotype shows the 23 pairs of
homologous chromosomes In humans
Chromosomes and Chromatin
In an nondividing
cell theDNA in the
nucleus is called?
What is this?
These “worms”
in the nucleus
are called?
DNA exists
as chromatin
during interphase
Chromosomes are
seen during mitosis
The Cell Cycle (Cell Division)
1. Interphase: Growth and DNA replication
(The chromosome number doubles).
2. Mitosis: The division of the nucleus
3. Cytokinesis: The division of the cytoplasm
The Purpose of Cell Division
1. Growth
2. Replacement of damaged cells
3. Asexual reproduction
Interphase
Mitosis
Cytokinesis
occurs during
telophase
DNA replication
occurs during
interphase
DNA Replication
Interphase
Phases of the Cell Cycle
• Interphase
– Growth and DNA replication
– Chromosomes have duplicated but they are still
in the form chromatin fibers
Phases of the Cell Cycle
• Prophase
– Chromosomes become visible
– Nucleolus disappears
– Nuclear membrane disappears
Phases of the Cell Cycle
• Metaphase
– Mitotic spindle fully formed
– Centromeres of chromosomes at “cell equator”
How many
chromosomes
are in this
cell?_____
Metaphase
Anaphase
How many
chromosomes
are in this
cell?_____
Spindle fibers
Pair of centrioles
How many
chromosomes
are in this
cell?_____
Metaphase
Anaphase
How many
chromosomes
are in this
cell?_____
Phases of the Cell Cycle
• Anaphase
– Sister chromatids of each replicated
chromosome separate creating identical
daughter chromosomes
Metaphase
Anaphase
Phases of the Cell Cycle
• Telophase
– Daughter chromosomes at opposite poles
– Cytokinesis begins
Animal Cell Cytokinesis
Plant Cell Cytokinesis
The Cell Cycle
Interphase
Mitosis
Cytokinesis: The division of cytoplasm
Interphase and Mitosis
The Human Life Cycle
Fertilization Creates Diploid Cells
Haploid
2
N = ___
Haploid
2
N = ___
B
+
Sperm
4
Diploid: N = ___
B
b
b
Egg
Zygote
B = Brown Eyes
b = Blue Eyes
Meiosis: The Production of Eggs and Sperm
• Somatic Cells: Typical body cells
– _____ Chromosomes
– _____ Pair of homologous chromosomes
– Diploid
• Gametes or Sex Cells: Eggs and sperm
– _____ Chromosomes
– Haploid
Meiosis Reduces the
Chromosome Number in Half
Homologue
inherited
from mom
Meiosis Is a Source of
Genetic Variation
Homologue
inherited from
dad
Homologous
chromosomes
exchanged pieces
Crossing Over
Crossing Over
Meiosis is a Source of Genetic Variation
Independent Assortment of Chromosomes
(The cell is committed to divide if it
passes this checkpoint)
Apoptosis:
Programmed Cell Death
G0 is an
extended
resting
period.
What might damage DNA?
Interphase
(The cell performs
its functions but
does not divide.)
Mitosis
Interphase
Interphase
Cancer: Uncontrolled Cell Division
• Benign Tumors
– Encapsulated
• Malignant Tumors
– Invasive
– Cells may leave the tumor and spread throughout the body
• Metastases
– Cells that leave a tumor and spread throughout the body
forming new tumors at distant sites
Angiogenesis:
The formation
of new blood
vessels that
bring oxygen
And nutrients to
a cancerous
tumor.
Prevention of Cancer
• Lung Cancer
• Skin Cancer
• Colon Cancer
p53: A gene that plays a key role in the G1 Checkpoint of Cell Division
(Apoptosis)