Cell Reproduction and DNA
History of Cells
• During the 17th century, the
invention of the microscope
helped scientists examine drops
of blood, scrapings from their
teeth, and other small things.
• In 1665, Robert Hooke cut a thin
slice of cork and looked at it under
his microscope…he saw squares
and named those squares cells.
http://www.youtube.com/watch?
v=4OpBylwH9DU
• In the 1830’s, plants were
examined an were determined to
be made of cells also.
The Cell Theory
Rudolph Virchow hypothesized that:
• All organisms are made up of one or more
cells
• The cell is the basic unit of organization in
organisms
• All cells come from cells
Cell Review
• There are two types
of cells:
• Prokaryotic cells don’t
have a nucleus.
• Ex: bacteria
• Eukaryotic cells have
a nucleus
• Ex. Plants and animal
cells
Cell Structures
• Cell walls: outer
coverings that protect
cells and give them
shape.
• Cytoplasm: gel like
substance that contains
the cytoskeleton…gives
and maintains shape of
the cell
• Organelles: the
structures inside of the
cell
Cell Structures
• Nucleus: directs all cell
activities…contains DNA
(information that contains the
code of all cell’s structure and
activities).
• Mitochondria: a structure where
energy is released from the
breakdown of food into CO2 and
water.
• Ribosomes: a structure that
makes proteins needed for
chemical reactions
Cell Division and Mitosis
• Cell division — increases the
number of cells and causes manycelled organisms to grow
• The Cell Cycle — series of events
that takes place from one cell
division to the next
• Cells have periods of
formation, growth and
development, and death
called life cycles.
• http://www.youtube.com/watc
h?v=L0k-enzoeOM
Cell Division and Mitosis
• Chromosome—structure in the
nucleus that contains hereditary
material
• Interphase — most of the life of
any eukaryotic cell, or cell with a
nucleus, is spent in a period of
growth and development.
• During interphase, a cell
duplicates its
chromosomes and
prepares for cell division.
• After interphase, the
nucleus divides, and then
the cytoplasm separates to
form two new cells.
• Mitosis - process in which the
nucleus divides to form two
identical nuclei
Prophase
• Nucleolus and nuclear membrane disintegrate.
• Centrioles move to opposite ends of the cell.
• Spindle fibers begin to stretch across the cell.
Metaphase
• Pairs of chromatids line up across the center of the
cell.
Anaphase
• Each centromere divides.
• Each pair of chromatids separates and moves to
opposite ends of the cell.
Telophase
• spindle fibers disappear and a new nucleus forms.
Animal vs. Plant Cells
• Cytokinesis: Division of
the Cytoplasm—for most
cells, the cytoplasm
separates after the nucleus
divides
In animal cells, the cell
membrane pinches in the
middle and the cytoplasm
divides.
In plant cells, a cell plate
forms.
Extra Large, Semi-3D Mitosis Thingy
• Divide into groups of 3-4.
• Using a large piece of paper, divide up
the steps of Mitosis, including Interphase,
and make a large diagram.
• All of the essential cell structures must be
labeled in each step.
• Describe what happens in each step.
• Pick one cell structure in each step and
make it 3D…a different structure must be
3D in each step.
Cell and Mitosis Quiz
1. Explain one of the main ideas of the Cell
Theory.
2. What is the function of the nucleus in the
cell?
3. In your own words, explain the purpose of
mitosis.
Results of Mitosis
• Each cell in your body, except sex cells, has
a nucleus with 46 chromosomes.
• Allows growth and replaces worn out or
damaged cells
Asexual reproduction — a new organism is
produced from one parent organism.
An organism with no nucleus divides
(bacteria) into two identical organisms by
fission.
Budding — a small, exact copy of the adult
grows from the body of the parent.
In regeneration, a whole new organism grows
from each piece of the parent.
Section 2: Sexual
Reproduction and Meiosis
Sexual reproduction—two sex cells,
usually an egg and a sperm, come
together.
Fertilization—the joining of an egg
and a sperm, generally from two
different organisms of the same
species
– Sperm are formed in the male
reproductive organs.
– Eggs are formed in the female
reproductive organs.
– A cell that forms from
fertilization is a zygote.
Following fertilization, cell division
begins and a new organism
develops.
Sexual Reproduction
Human sex cells are
haploid, because they
have 23 single
chromosomes
Human body cells are
diploid, because they
have 23 pairs of similar
chromosomes = 46 total
chromosomes.
In Meiosis I, each chromosome is duplicated, just as in
mitosis. The steps of Meiosis I are identical to mitosis…
http://www.youtube.com/watch?v=qCLmR9-YY7o&feature=fvsr
In meiosis II, the nuclei divide and the chromatids separate,
producing four cells with half the number of chromosomes of the
original nucleus.
Prophase II: Duplicated chromosomes and spindle fibers
reappear in each new cell.
Metaphase II: Duplicated chromosomes move to the center of
the cell. Each centromere now attaches to two spindle fibers
instead of one.
Anaphase II: The centromere divides and the chromatids
separate and move to opposite ends of the cell. Each chromatid
is now an individual chromosome.
Telophase II: Spindle fibers disappear, nuclear membrane forms
around each set of chromosomes, cytoplasm divides
Mitosis/Meiosis Venn Diagram
• You must have at least 4 points in each
section (12 total)
• You must include 4 pictures in each
section…
• They can correspond with your 4 points or
can be separate.
Chapter 4
Section 3
DNA – Deoxyribonucleic Acid:
– a chemical that contains information that an organism
needs to grow and function
– Watson and Crick described first accurate model of
DNA in 1953.
• They were awarded the Nobel Prize for physiology
in 1962
• Some scientists believe the discovery of DNA was
the most important biological event of the century
• Why? – Led to improved plants and animals, and
to help in detecting and preventing inherited
disorders
http://www.youtube.com/watch?v=hnSPGlpZx_Q
The structure of DNA is
similar to a twisted ladder.
• The sides of the
ladder are made up
of sugar-phosphate
molecules.
• The rungs of the
ladder are made up
of nitrogen bases.
• The 4 nitrogen
bases are Adenine,
Thymine, Guanine
and Cytosine.
• Adenine always
pairs with Thymine
• Guanine always
pairs with Cytosine
• Before a cell
divides, its DNA
duplicates itself by
unwinding and
separating its sides.
• Each side becomes
a pattern on which a
new side forms.
• Genes – sections of
DNA on a
chromosome
• Unit of heredity
• Contain
instructions for
making specific
proteins
DNA Double Helix Replica
Day One/Two
1.
Take 2 “backbone” sheets,
and 1 of each of the colored
sheets of base pairs.
2.
Cut out one sheet of
“backbone” pieces and half of
each of the base pairs.
3.
Using your DNA blueprint,
assemble your DNA double
helix (Only bolded base
pairs today).
4.
Make sure you pair the
correct base pairs together!
• RNA carries the codes for
making proteins from the
nucleus to the ribosomes
in the cytoplasm.
• Messenger RNA
carries the code
that directs the
order in which the
amino acids bond.
• Ribosomal RNA
makes up
ribosomes, where
proteins are built.
• Transfer RNA
brings amino
acids to the
ribosomes to build
the protein.
• RNA has nitrogen
bases like DNA but
contains Uracil
instead of Thymine.
So..
• Adenine pairs with
Uracil
•Guanine pairs with
Cytosine
• Mutations - any permanent
change in the DNA
sequence of a cell's gene or
chromosome
– Can be caused by
outside factors like X
rays, sunlight, and some
chemicals
– A change in a gene or
chromosome can change
the traits of an organism.