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TOPIC 1 : Introduction
to the Cell & Cell
Theory
The Cell Theory
1. All living things are composed
of one or more cells.
2. Cells are the basic units of
structure and function in an
organism.
3. Cells come only from existing
cells.
Cells are Diverse…
both in size,
shape, and
internal
organization.
Why Are Cells So Small?
Transport-
Cell volume to
surface area ratios favor small
size.
Control- Nucleus to cytoplasm
consideration.
How small can a cell be?
Mycoplasmas - bacteria that are 0.1 to 1.0
mm. (1/10 the size of regular bacteria).
Note: 1.0 mm = one millionth of a meter
All cells have……
Plasma
(cell) Membrane
Nucleus (eukaryotes only)
Cytoplasm (an area)
Organelles (structures with
specialized functions)
Cell Types
Prokaryotes- simple cells that do
not have internal membranes
example = bacteria
Eukaryotes- more complex cells
that do have internal,
membrane-bound structures
examples = plants and animals
Timeline
Prokaryotic
Organisms:
First appeared
3.5 BYA
include bacteria
and cyanobacteria
Eukaryotic
Organisms:
First appeared
2.0 BYA
include protists,
fungi, plants and
animals
Key Differences:
Prokaryotes
• Lack a nucleus and
other membrane
bounded structures.
• Have small ribosomes
• DNA is not organized
into chromosomes
• Flagella are not made of
microtubules and does
not have a 9+2 structure
• Cell walls are made of
peptidoglycan, not
cellulose
Eukaryotes
•
•
•
•
•
Have a nucleus and other
membrane bounded
structures.
Have large ribosomes
DNA is organized into
chromosomes
Flagella are made of
microtubules and have a
9+2 structure
Cell walls are made of
cellulose
Examples
Prokaryotic
Eukaryotic
Nucleus
Eukaryotic
Prokaryotic
TOPIC 2 : The
Organization of Living
Things
Key Concept

As multicellular
organisms develop,
their cells differentiate
(change & separate)
and form levels of
organization

Why it Matters:
 Humans
(we are
multicellular) can
have different kinds of
cells, tissues, organs,
and organ systems
Unicellular Organisms

“uni-” = one

Prokaryotes are unicellular organisms

Some algae, some protists, and some eukaryotes (yeasts), are
unicellular

Can still do everything they need to stay alive

Benefits over multicellular organisms:

Need fewer resources

Can live in harsher conditions
Multicellular Organisms
“multi-” = more than one
 Plants, animals, some protists, and most
fungi are multicellular


Start as a single cell  many cells  cells
differentiate (change) into different types of
cells  cells group together
Multicellular Characteristics
Larger size = have less predators and have
more options of things to eat
 Longer life – organism will continue to live even
if a single cell dies


Specialization – each type of cell has a
specific job, making the organism more
efficient
Levels of Organization
1st Level: Cells
 2nd Level: Tissues
 3rd Level: Organs
 4th Level: Organ Systems


Cells  Tissues  Organs  Organ Systems
Level 1 : Cells

Cells can be specialized
(have a certain function)

Function = job

Function is related to the
cell structure

Structure = how parts of the
cell are put together
 Shape
 Material

it’s made from
Structure of a brain cell is
different from muscle cell
Level 2: Tissues
Tissue = group of cells that work together to do
a specific job
 Ex: Heart muscle tissue
is made of heart muscle
cells

Animals have 4 types of
tissue: nerve, muscle,
connective, protective
 Plants have 3 types of
tissue : transport, protective, ground

Level 3: Organs

Organ = structure that is made up of 2 or more
tissues working together to get a specific job done

Ex: Stomach – muscle tissue moves food, special
tissues make chemicals to digest food, connective
tissue holds stomach together, nervous tissue sends
messages back and forth between the stomach
and brain
Level 4: Organ Systems

Organ system = group of organs working together to perform
a specific function

Each organ system has a specific job

Ex: Digestive system is made of several organs including the
stomach and intestines
Structure of Animals
Cells
-basic unit of an animal’s structure
-become specialized
_______________________________
Tissues
-made of cells that work together to perform a specific function
__________________________________________
Organs
-made of different types of tissues that work together to perform a specific function
____________________________________________________
Organ Systems
-made of organs that work together to perform a specific function
_____________________________________________________________
Organisms
TOPIC 3: GENETICS
Early Genetics
• The study of genetics
began with observations
made by Gregor Mendel.
• After noticing that the
flowers his pea plants were
either violet or white,
Mendel began to study
the segregation of
heritable traits.
Between 1856 and 1863
he cultivated and tested
at least 28,000 pea
plants.
Remember that Mendel worked almost 150 years ago when nobody
knew about genes or even the structures (chromosomes) that carry
genes.
Here are some traits
observed by Mendel:
Let’s consider a single gene…
• A gene carries
information that
determines your
traits. Traits are
characteristics you
inherit from your
parents.
• Genes are located in
chromosomes.
• Chromosomes come
in pairs and there are
thousands, of genes
in one chromosome.
Continued…
• In humans, a cell’s nucleus
contains 46 individual
chromosomes or 23 pairs of
chromosomes.
• Half of the chromosomes
come from one parent
and half come from the
other parent.
Here is the detailed
structure of a
chromosome
This is a human
karyotype
representing the 23
pairs of
chromosomes in a
male
Definitions
• Allele- discrete version of the same gene
• Genotype- the genes of an organism for one
specific trait
• Phenotype- the physical appearance of a
trait in an organism
Definitions
• Dominant trait refers to a genetic feature that “hides” the
recessive trait in the phenotype of an individual.
• The term "recessive” describes a trait that is covered over (or
dominated) by another form of that trait and seems to
disappear.
• Homozygous= two alleles that are the same for a trait (Pure)
• Heterozygous= two different alleles for a trait (Hybrid)
• Genetics – study of how traits are passed from parent
to offspring
• Traits are determined by the genes on the
chromosomes.
• A gene is a segment of DNA that determines a trait.
• Chromosomes come in homologous pairs, thus genes
come in pairs.
Homologous pairs – matching genes – one from female
parent and one from male parent
• Example: Humans have 46 chromosomes or 23 pairs.
One set from dad – 23 in sperm
One set from mom – 23 in egg
• One pair of Homologous Chromosomes:
Gene for eye color
(blue eyes)
Homologous pair
of chromosomes
Gene for eye color
(brown eyes)
Alleles – different genes (possibilities) for the same trait –
ex: blue eyes or brown eyes
Dominant and Recessive Genes
• Gene that prevents the other gene from “showing” –
dominant
• Gene that does NOT “show” even though it is present –
recessive
• Symbol – Dominant gene – upper case letter – T
Recessive gene – lower case letter – t
Dominant
color
Recessive
color
• Both genes of a pair are the same –
homozygous or purebred
TT – homozygous dominant
tt – homozygous recessive
• One dominant and one recessive gene –
heterozygous or hybrid
Tt – heterozygous
BB – Black
Bb – Black w/
white
gene
bb –
White
Genotype and Phenotype
• Combination of genes an organism has (actual gene
makeup) – genotype
Ex: TT, Tt, tt
• Physical appearance resulting from gene make-up –
phenotype
Ex: hitchhiker’s thumb or straight thumb
Punnett Square and Probability
• Used to predict the possible gene makeup of offspring –
Punnett Square
• Example: Black fur (B) is dominant to white fur (b) in mice
1. Cross a heterozygous male with a homozygous recessive female.
Black fur (B)
Heterozygous
male
White fur (b)
White fur (b)
Homozygous
recessive female
White fur (b)
Practice
•
We use two letters to represent the genotype. A capital letter
represents the dominant form of a gene (allele) and a lowercase
letter is the abbreviation for the recessive form of the gene
(allele).
•
Example below: P=dominant purple and p= recessive white
The phenotype for this
flower is violet while
its genotype (if
homozygous) is PP.
The phenotype for this
flower is white while
its genotype is pp (to
be white the flower
must have two of the
recessive copies of the
allele).
Punnett Squares
 The
Punnett square is
the standard way of
working out what the
possible offspring of
two parents will be.
 It
is a helpful tool to
show allelic
combinations and
predict offspring
ratios.
Before we go further lets review how to set up a
Punnett Square…
We begin by constructing a grid of two perpendicular lines.
Next, put the genotype of one parent across
the top and the other along the left side.
For this example lets consider a genotype of BB crossed with bb.
B
b
b
B
• Notice only one
letter goes above
each box
• It does not matter
which parent’s
genotype goes on
either side.
Next, fill in the boxes by copying the column and row head-letters
down and across into
the empty spaces.
B
B
b
Bb
Bb
b
Bb
Bb
Punnett Squares
Now
that we have learned the
basics of genetics lets walk
through some examples using
Punnett Squares.
W
w
WWW Ww
w Ww ww
Usually write the
capital letter first
Lets say:
W- dominant white
w- recessive violet
Parents in this cross are heterozygous (Ww).
Note: Make sure I can tell your capital letters from
lowercase letters.
What percentage of the offspring will have violet
flowers?
ANSWER: 25% (homozygous recessive)
Red hair (R) is dominant over blond hair (r). Make a
cross between a heterozygous red head and a
blond.
R
r
r
r
Rr
rr
Rr
rr
What percentage of the offspring will have red hair? 50%
Let’s try some more…
In pea plants, tall pea plants (T) are dominant
over short pea plants (t). Construct a Punnett
Square for a heterozygous tall pea plant and a
short pea plant.
t
t
T
Tt
Tt
t
tt
tt
What are the
percentage of
phenotypes?
50% tall
50% short
Black eyes (R) is dominant over red eyes (r)
in rats. Make a cross between a
homozygous rat with black eyes and a
rat with red eyes.
r
r
R
Rr
Rr
R
Rr
Rr
What is the possibility of
a red eye off springs?
0%
