First semester Study GUIDE
This study guide is designed to reinforce your knowledge of biology. This study guide
can be used with your practice END OF COURSE (EOC) tests.
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Please use the space below to write any questions you have over the practice EOC
test or the study guide. If you need help on a specific question or topic, please write
your concerns down. This is given to you as an aid and should be used. I’m just trying
to give you everything you need to be successful.
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- Biology Process
• Demonstrate knowledge of inquiry techniques
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Questions that will come from these will look a lot like the questions from the ACT practice
we have been doing. You need to feel comfortable reading data from charts and graphs.
Questions will also see if you completely understand the scientific process.
o The scientific process:
 Observation- observing of the natural world or phenomenon that has taken
place
 Question- Form question about the observation.
 Hypothesis- Making an explanation about an observation (your educated
guess).
 Experiment- Conduct an experiment
 Experiment should be controlled meaning only one variable should
change. Should be done more than once to ensure accuracy.
o Manipulated variable (Independent Variable)- The variable
you change on purpose
o Responding variable (Dependent Variable)- Variable that
changes during the experiment due to the manipulated
variable
o Controlled variable – Variables that stay the same.
 Record data- Record data in graphs or tables
 Form a conclusion- based on your experimental results produce a conclusion
from the question. (what did you learn from the results.)
Questions on the EOC test will give you simulated experiments and ask you to find the
problems within the scientific process, whether it be an experiment that is wrong or identify
the different variables.
• Use mathematics and measurement; use graphical and mathematical models
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Questions from this area will ask you to read data from graphs, charts and passages.
• Identify criteria necessary to characterize life; define biological organization levels
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Questions from this topic will include understanding of characteristics of life and biological
organization.
o Characteristics of life include:
 Living things are made up of units called cells.
 Living things reproduce
 Living things are based on a universal genetic code
o
 Living things grow and develop
 Living things obtain and use materials and energy
 Living things respond to their environment
 Taken as group living things change over time (evolve)
Biological organization -Remember BIO means living
 Cells
 Tissue
 Organs
 Organ systems
 organism
- Biochemistry; Cell
• Describe atomic structure, bonding between atoms, organic and inorganic compounds,
Enzymes, and ATP
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Atomic structure- atoms are composed of neutrons, protons, electrons
o
o
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Protons- Positively charged; located in the nucleus
Neutrons- NO CHARGE; located in the nucleus
Electrons- Negative charge; located in clouds/shells outside the nucleus
 Valence electrons- electrons in the outer-most shell
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Octet rule- All ATOMS strive to have 8 (OCT) electrons in their outer
most shell/ except the first shell which can contain 2.
Bonding between atoms -can occur two MAIN ways; Covalent bonding, and Ionic bonding
o Covalent bonding
 Occurs when two atoms share electrons- Hence the CO =cooperative
 Keep in mind the octet rule from above. Atoms strive to reach 8 valence
electrons. EX. Water= H2O. Hydrogen has 1 electron in its first shell and
only needs one more. Oxygen has 6 valence electrons and only needs two to
achieve the octet. Therefore it takes two hydrogen sharing two different
electrons to equal a total of 8 for the Oxygen and each hydrogen atom is
sharing 2 electrons with the oxygen.
o
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Ionic bonding
 Ionic bonds occur when atoms give away or take electrons to obtain
the octet rule.
 When atoms give away electrons, they change to a net positive charge.
When atoms take an electron, they change to a net negative charge.
Organic compounds- are compounds that are formed of carbon chains (C-C-C-C) and are
extremely important to life. There are four main organic compound groups: Carbohydrates,
Lipids, Proteins, and Nucleic Acids. All four of these organic compounds are made from the
following elements: sulfur, phosphorus, oxygen, nitrogen, carbon, hydrogen (SPONCH)
o
Carbohydrates- are sugar molecules and are the compound we living things get our
energy from. We take in Carbohydrates break them down in the presence of
oxygen, to release the energy they have. There are different types of Cabohydrates:
 Simple carbohydrates (sugars)- These carbohydrates are formed from one
single sugar molecule and include glucose, fructose. Anything ending in OSE
is a carbohydrate.
 Complex carbohydrates- These carbohydrates are formed from two or more
single sugar molecules bonding together to form large chains of single
sugars. An example of these would include: Starch, Chitin, and Cellulose.
o Lipids- Are large carbon based compounds that living things use to store energy.
They include fats oils waxes and steroids. These molecules are hydrophobic
(water hating), which means they do not dissolve in water. This is why they can
be found in the cell membrane. The lipids in the cells membrane water-proof
our cells.
o Proteins- Proteins can arguably be the most important organic molecule. Think
about it, DNA is housed in a protective covering called the nucleus, and never
leaves that protection. DNA contains the information for our cells to build
proteins.
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o
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Proteins can be structural which means they build important structures
of our body. They can also be functional, which means they regulate a
lot of the chemical processes that occur in the body.
Nucleic acids- These organic molecules are the building blocks for our DNA,
they build structure called nucleotides, which are the sub-units or DNA.
 DNA- is the genetic material of our bodies. It is responsible for holding
all the information for all cellular activities. DNA is also the molecule
that allows us to pass on our genetic information to our children.
 DNA structure- DNA is a huge molecule that takes the shape of
a double helix (twisted ladder).
 DNA is made up of subunits called nucleotides with consist of
a phosphate backbone (sides of ladder), 5 carbon sugar
(Deoxyribose), and a nitrogenous base. DNA consists of only 4
different nitrogen bases; Adenine, Thymine, Adenine,
Guanine. (AT, CG)
These bases pair up in a certain way; A-T, G-C
 On a side note DNA and RNA are closely related, but different in a
few ways:
o DNA is double stranded, RNA is single stranded
o DNA contains the nitrogenous bas of Thymine, RNA replaces
Thymine with Uracil.
o DNA never leaves the nucleus; RNA leaves the nucleus
carrying with it the information to build proteins.
Inorganic molecules- Molecules that do not have a carbon backbone. EX. FeO (Iron Oxide),
NaCl (table salt).
Enzymes- Are specialized proteins that speed up chemical reactions in living things.
Anything ending in ASE can be considered an enzyme. An example would be LACTASE,
which is the specific enzyme that acts on LACTOSE, The sugar found in Dairy products.
People who are Lactose intolerant Lack the enzyme LACTASE which allows for the
breakdown of this sugar.
Since DNA codes for proteins, and people that are lactose intolerant lack the enzyme
Lactase (a protein), it can be traced back to a problem with their DNA.
ATP- Is a chemical compound that has the ability to store small amounts of energy. ATP is
produced from glucose in the presence of oxygen in the mitochondria. Glucose is also an
energy containing molecule. Glucose contains way too much energy for our cells to use
directly, so our cells go through a process called cellular respiration to produce ATP which
contains less energy. One molecule of glucose is equal to 38 ATP. Now that energy has been
contained in ATP, the cell uses it for all cellular activities. Anything the cell does that
requires energy uses ATP.
o
Structure of ATP- ATP is Adenosine triphosphate. The TRI in front of phosphate
means there are three phosphate molecules attached. These three phosphates are
very important, because the energy all of our cells use is stored in the last
phosphate to phosphate bond (P-P). When that bond is broken, it releases the
energy. After the energy is released ATP turns into ADP. Because the release of
energy caused the 3rd phosphate to be broken off Adenosine Triphosphate (3
Phosphates), the molecule is now called ADP= Adenosine Diphosphate (Di meaning
2 phosphate). ADP can and is recycled back into ATP by attaching another
phosphate, which requires energy. This energy comes from the energy carrying
molecule glucose.
• Explain properties of water and describe pH of a solution
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Questions from this area will test your understanding of water and its properties. You will
also be tested on your ability to understand the PH scale
o Properties of water- Water is formed when two hydrogen atoms combine with one
oxygen atom. This chemical reaction takes a lot of energy to get started, that is why
all the hydrogen and oxygen in the atmosphere doesn’t combine and form water. \
 Water is a polar molecule which is its most important property. Water is
polar, since it has an uneven distribution of electrons. There are more
electrons surrounding the oxygen, giving that area a net negative charge.
And the area around the hydrogen a net positive charge. Thus, a water
molecule acts like a magnet with a + and – end. This is what gives water
molecules the ability to stick to each other.
 Water being a polar molecule also allows it to dissolve a lot of other
compounds.
o
The PH scale- The PH scale is a numerical scale going from 1 to 14, and 7 being
neutral (pure water). Measures the strength of acids and bases.
 The lower the number the more acidic a solution is. As the number goes
lower from 7 more H+ ions get produced in the solution making it a
stronger acid.
 As the number gets higher from 7 the more basic the solution. As the
solution gets more basic there are more OH- ions (hydroxide ions)
produced.
 More H+ ions than OH- ions the solution is acidic. The greater the
difference the stronger the acid
 More OH- ions than H+ ions the solution is basic. The greater the
difference the stronger the base.
• Identify cell types and describe functions of cellular organelles
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Questions from this area will test your knowledge of cells and cell structure.
o There are two main types of cells:
 Prokaryotic cells- have no nucleus
 These types of cells include Bacteria

Eukaryotic cells- These types of cells contain a nucleus and other
membrane enclosed organelles. Two main types of Eukaryotic cells are
plant and animal cells.
o
Eukaryotic/animal cell structure (Organelles)
 Nucleus- is a membrane enclosed structure that
contains and protects DNA. Ribosomes are made in a
dense region of the nucleus called the nucleolus. It
contains pores, which are openings. These pores are
there for mRNA to carry information from DNA outside
the nucleus. DNA never leaves the nucleus. On a side
note, DNA can also be found in the mitochondria of
eukaryotic cells.
 Cell membrane- is a double layer (bi-layer) surrounding
the entire cell. The cell membrane monitors what
enters and leaves the cell. It is the bouncer. This layer is
made up of a phospholipid bi-layer, and can be called
the phospholipid bi-layer as well.
 Mitochondria- A membrane enclosed organelle that
produces energy in the form of ATP for the cell. ATP is
the energy type that all cells use for all cellular
activities. Because our muscle cells use lots of energy,
they contain more mitochondria than other cells in the
human body. Mitochondria are the site where the
o
oxygen we breathe and glucose (sugar/ carbohydrates)
we eat meet, and the energy in glucose is transformed
through a process called cellular respiration into ATP.
We exhale the byproducts of Carbon dioxide (CO2),
water vapor (H20), and heat. (That’s the reason you can
fog up a window. )
 Ribosomes- These tiny organelles are the site of protein
production. DNA contains the information to make
specific proteins; mRNA is made in the nucleus, through
a process called translation, and carried out of the
nucleus through nuclear pores. mRNA now carries the
information to make proteins to a ribosome where a
process called transcription builds a protein your body
needs.
 Endoplasmic reticulum- Is a membrane enclosed
organelle that creates passage ways throughout the
cell. The rough ER has ribosomes attached and helps
aid in protein production. The smooth ER aids in lipid
production.
 Golgi Apparatus- When proteins are made in the rough
ER or on free floating ribosomes, they are sent to the
golgi apparatus. This organelle modifies, and encloses
the protein in a vesicle (bubble), then ships the protein
to where it is needed. The Golgi apparatus can be
looked at as the UPS of the cell; it modifies, and ships
packages of proteins.
 Vacuole- A membrane enclosed organelle, which stores
carbohydrates (sugars), Lipids (fats), and proteins.
Plant cells- Are cells that make up the structure of plants. Plant
cells have all the listed organelles of animal cells with a few
added: Chloroplast, Large central vacuole, cell wall.
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Chloroplasts- Specialized organelle only found in plant
cells. Is the location of photosynthesis. Contains the
pigment chlorophyll, which makes the plants green.
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Photosynthesis- The process of capturing light
energy and using that energy to convert Carbon
Dioxide (CO2) and Water (H2O) into glucose
(C6H12O6) and Oxygen (O2). The chemical
equation for photosynthesis is 6CO2 + 6H2O
C6H12O6 + 6O2 + ENERGY. So basically
photosynthesis takes energy from the sun and
stores it in a molecule of glucose.
• Describe movement of substances into and out of cells
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This area of the test will test your knowledge of the following processes, which allow
substances to pass through or out of the cell membrane: Diffusion, Osmosis, Active
transport, passive transport, endocytosis, and exocytosis. All these processes take place on
our cell membranes because they are semipermeable. Semipermeable means small things
can pass through and larger things can’t pass through.
o Diffusion- Is the movement of particles (molecules) from high concentration from
low concentration. This movement from high concentration to low concentration is
called the concentration gradient). Ex. Spray perfume into the air and the scent
(molecules) will spread (diffuse) throughout the room, from the area you sprayed
(high concentration) to areas it is not located (low concentration). The particles
(molecules) of scent will continue to diffuse and move throughout the room until it
reaches an equilibrium. Equilibrium means all molecules are spread out equally.
o
Osmosis- Is simply the diffusion of water. Some molecules are too large to diffuse
across a membrane (cell membrane). When this happens water will dissolve
through the membrane until an equal concentration is reached on both sides
(equilibrium).
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There are three types of solutions when dealing with osmosis: Hypotonic,
isotonic, and hypertonic.
 Hypotonic- Hypo means below. So the solution is less concentrated
than the cell placed in it. To equal out the concentrations of the cell
and the solution, water rushes in and causes the cell to swell. The
cells will swell until it bursts or equilibrium is reached. This is why it
is not a good idea to drink distilled water. Distilled water is
hypotonic compared to our red blood cells. The hypotonic distilled
water causes water to rush into our cells and causes our cells to
swell. A woman died a few years ago trying to win a water drinking
contest. The contest stated; whoever drinks the most water wins a
xbox. The people putting on the contest never thought about
osmosis and had the contestants drink distilled water. The woman
who died drank so much of the distilled water her red blood cells
swelled and bursts, which lead to a stroke.
 Isotonic- Iso means equal. So this means that the solution has the
same concentration as the cell placed in the solution. Water does
not rush in and the cell placed in the isotonic solution stays the
same size. An example of an isotonic solution is IV fluids. Hospitals
us IV fluids to hydrate patients. Because the IV is isotonic it doesn’t
cause cells to swell/burst or shrink.
 Hypertonic- Hyper means above. So the solution the cell is placed in
has a higher concentration the cell itself. To equal out this
concentration water rushes out of the cell, trying to water down the
highly concentrated solution it is placed in. This is the exact reason
humans can’t drink saltwater. The saltwater is hypertonic, and
causes our cells to lose water, which dehydrates use even further.
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Passive transport- This is the category of transport that doesn’t require
energy from the cell. These types of transport rely on the principles of
physics. Diffusion and osmosis are both types of passive transport.
Active transport- This is a category of transport that requires energy
from our cells, in the form of ATP, to move things across the cell
membrane. These types of transport include; Protein pump mediated
transport, endocytosis, and exocytosis.
o Protein pump mediated transport- This type of transport across
the cell membrane relies on a protein pump, which acts like a
door way or a gate into the cell. It takes energy to work this
pump (doorway). These protein mediated pumps bring in
molecules that are too large to diffuse across the membrane or
they can pump things across the concentration gradient (From
low concentration to high concentration).
o
Endocytosis- is the process of bringing things into the cell by
folding the cell membrane and creating a pocket. There are two
types of endocytosis; Pinocytosis, phagocytosis.
 Pinocytosis- the process of bringing in liquid. The name
pinocytosis literally means cell drinking.
 Phagocytosis- The process of bringing in solids. The
name literally means cell eating.
o
Exocytosis- The process of releasing materials through vesicles
(bubbles) forming with the cell membrane.
• Describe cellular respiration.
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During this portion of the test you will be tested on your knowledge of cellular respiration.
o Cellular respiration -is the process of living things taking in oxygen and glucose to
produce energy in the form of ATP. Cellular respiration can be broken down into
smaller processes. What you need to keep in mind that all living things are chemical
factories, we are constantly taking in molecules and breaking them down and
building new molecules. Every second there are thousands of chemical reactions
taking place in your body, which break down molecules into smaller ones and then
building new molecules. Cellular respiration is a process and can be divided into
different stages; Glycolysis, Krebs cycle also called the citric acid cycle, and the
electron transport chain. The steps in which your body creates ATP (energy), when
oxygen is present is 1. Glycolysis, Krebs cycle, electron transport chain. When
oxygen is present it is called aerobic respiration. The starting materials for these
processes are oxygen and glucose, which we inhale and consume with food. The
chemical equation for cellular respiration is: C6H12O6+ 6O2
Energy+ 6CO2+
6H2O.
 Glycolysis- beginning step in cellular respiration, and creates 2 ATP
molecules and also creates the substances required for the Krebs cycle.
 The Krebs cycle- Begins when glycolysis ends and creates 2 more ATP. Krebs
cycle also creates free electrons, which are needed during the Next step;
Electron transport chain.
 Electron transport chain- is the final stage of cellular respiration, and
creates 34 ATP.
o
Anaerobic respiration- When Oxygen is absence (anaerobic respiration), like when
you get out of breath, living things can still convert glucose into ATP through process
call Lactic acid fermentation. Although we can create energy without oxygen we can
only do it for a short period of time. Lactic acid fermentation creates ATP and lactic
acid. This process happens in humans when we get out of breath. The lactic acid
formed from this is stored in our muscles in a crystal form (sharp edges). These
lactic acid crystals rip and tear our muscles and cause us to become sore.
• Describe cell division and mitosis
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Questions from this part of the test will test your knowledge on Cell division
o When looking at cell division, we need to understand the cell cycle. The cell cycle is
the life stages of a cell. Just like we go through life stages (infancy, child, preteen,
teen, adult), a cell goes through life stages as well. The stages of the cell cycle in
order are as follow; G1, S, G2, mitosis, cytokinesis. The g1, S, G2 phases are
combined and called Interphase.
 G1- Is the Growth phase. The cell grows and prepares to copy the DNA.
 S- The S phase is when DNA is replicated. It is very important to replicate
the DNA of a cell. A human cell has 46 individual chromosomes, if the s
phase doesn’t happen the resulting 2 daughter cells will only have half the
DNA needed and the cell will die. So in human cells the s phase will cause 46
individual chromosomes to double into 92.
 DNA replication- the process involving DNA polymerase (unzips and
unwinds DNA and build back the corresponding sides) the copies
the DNA molecule.
 G2- The g2 phase is the phase when the cell continues to grow and mature.
 Mitosis- Mitosis is defined as the dividing of the nucleus only. NOT THE
SPLITTING OF THE CELL. Mitosis occurs in our somatic cells, which are all our
body cells. Mitosis take place in every cell we have, except our sex cells
(sperm and egg). Mitosis can be broken down into different phases. In order
the phases of mitosis are: prophase, metaphase, anaphase, telophase. A
good way to remember the sequence is to remember PMAT.
 Prophase- The Loosely wound DNA tightens up on proteins called
histones, to form tightly wound packages of dense genetic material
called chromosomes. The nucleus also starts to break apart.
 Metaphase- Is the phase at which all the chromosomes line up at
the equator (middle) of the cell. Once all the chromosomes are lined
up metaphase is over.
 Anaphase- Is the phase in which the chromosomes are pulled apart
toward each end of the cell. Each side of the cell will get a full and
complete copy of genetic material. In humans 92 chromosomes line
up and each side of the cell will get 46 (a complete set). Anaphase is
over when each side of the cell receives the chromosomes.
 Telophase- is the process of the nuclei (plural for nucleus) starts to
reform. During this phase each area of DNA will be enclosed by a
new nuclear membrane.
 Cytokinesis- Takes place at the same time as telophase. Cytokinesis is the
actual splitting of the cell.
 Cytokinesis in plant cells doesn’t involve the pinching of the two
plant cells, but the formation of a cell plate (new cell wall) between
the two new nuclei.
 Once all these steps have been accomplished, the cell cycle starts back over
at the G1 phase.
-Genetics; Evolution
• Describe basic structure and function of DNA, RNA, and proteins
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Questions from this part of the test will test your knowledge on how DNA can be translated
into RNA and the process of RNA Transcribing into a protein.
o First, A few important things we should understand at this point:
 DNA is made up of sub-units called nucleotides.
 These nucleotides arrange themselves into a structure called Double helix
 DNA is located in the nucleus.
 A protein is a chain of Amino Acids held together by polypeptide bonds.
Proteins can be huge, hundreds of amino acids long.
 Ribosomes are the site of ribosome production.
o
DNA structure Made up of sub-units called nucleotides. These nucleotides are made up of
even smaller units: Phosphate group, Deoxyribose (5-Carbon sugar), and a
nitrogenous base.
NUCLEOTIDE
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The actual double helix structure of DNA occurs when these nucleotides
attach to each other, as shown below.
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o
In a DNA molecule the phosphorus group and the deoxyribose group (S)
are the actual sides of the molecule.
 The nitrogenous bases are the bases that make up the runs of the
twisted ladder shape.
o There are four nitrogenous bases: Adenine, Thymine, Guanine,
and Cytosine. These bases only pare up a certain way. Adenine
with Thymine, and Guanine with Cytosine.
 DNA can make copies of its self in a process called replication, which
takes place in the nucleus with the help of an enzyme called DNA
polymerase.
RNA structure- RNA is a molecule that is closely related to DNA with only a few
key differences. The differences are as follows:
 RNA is single stranded
 RNA replaces Thymine with Uracil
 RNA can leave the nucleus.
 There are three main types of RNA:
 mRNA- The RNA that leaves the nucleus, carrying with it
the information to build a protein. The mRNA is created
in the nucleus through a process called transcription.
mRNA then leaves and attaches itself to a ribosome.


o
tRNA- This RNA molecule is attached to an amino acid.
tRNA lines up with mRNA from the nucleus and attaches
its amino acid to the one before it. As more molecules
of tRNA line up with the mRNA a chain of amino acids
form, this is a protein. Remember a protein is a chain of
amino acids linked together. This process of tRNA lining
up with mRNA and creating the protein is called
translation.
o Differences between mRNA and tRNA are
simple. mRNA is a longer molecule. tRNA is
short and has an attached amino acid.
rRNA- The ribosome organelle is actually made from an
RNA molecule. And this molecule of RNA that makes the
ribosome is called rRNA.
Protein structure- Are made from information stored in DNA. That information
leaves the nucleus in the form of mRNA and attaches to a ribosome, where
tRNA attaches amino acids together to form a long chain of amino acids called a
protein.
 Proteins are a chain of amino acids help together by polypeptide bonds.
Proteins can wind and form very complex structures.
• Describe meiosis
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Meiosis is the process of one germ cell, going through 2 divisions, and creating 4 gametes
(sex cells). This division is a reduction division which means the resulting daughter cells will
have less genetic material than the starting germ cell. This type of division only takes place
in the formation of gametes. The process of meiosis can be divided into 2 major divisions:
Meiosis 1 and Meiosis 2.
o Meiosis 1 – The first division. DNA has already been duplicated. In humans 46 has
been doubled to 92 total chromosomes. The first division results in 2 daughter cells
that contain 46 total chromosomes in humans. The first division is almost identical
o
o
to mitosis. The cell goes through prophase, metaphase, anaphase, telophase. And
cytokinesis. The main difference between meiosis 1 and mitosis is, during
metaphase of meiosis 1 crossing over occurs. Crossing over is the process of
exchanging DNA on homologous chromosome. Remember you have two copies of
every chromosome (One copy from each parent). The two chromosomes you have
for a given pair are called homologous (Homo = same). So during crossing over the
genetic information you have on one homologous pair is shuffled like a deck of
cards. This crossing over results in greater genetic variety.
Meiosis 2- Starts directly after cytokinesis of meiosis 1. It too goes through the same
phases: Prophase, Metaphase, Anaphase, Telophase, and cytokinesis. The main
thing to remember is meiosis 2 is the dividing of two cells with 46 chromosomes
into 4 cells with 23 chromosomes (in humans). Each of the four resulting cells
contains exactly 1 copy of each chromosome.
 Diploid (Di = 2)- a cell that contains 2 copies of every chromosome.
 Haploid (Hap = Half) - A cell that contains 1 copy of every chromosome.
Contains half the genetic information.
Meiosis starts with one diploid cell and ends with 4 genetically different haploid sex
cells. The sex cells will unite during sexual reproduction and create one diploid cell
with all the information to form a multicellular organism (human). You were once
one single cell caused by the uniting of two haploid cells, and the resulting single
diploid cell divided through mitosis to create you, and as an adult you will have over
50 trillion individual cells.
• Use correct terminology when working with genetic crosses
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This area of the test will test your knowledge of Punnett Squares and the terminology that
goes with it. When doing genetic crosses you need to understand that some traits exhibit
different characteristics than others. Some traits are simply dominant or recessive; others
are incomplete dominant and co-dominant. It is also very important to remember sex-linked
genes. These are genes that are found on the sex chromosomes (XY). The following terms
are those you need to understand to perform Genetic crosses. While reading these
definitions and looking at the example Punnett Square, you should know the following:
Most traits are controlled by 2 genes, one from your mother and one from your father. You
have two copies of each gene. The physical trait showed through gene expression depends
on the types of alleles you have. Ex. (If you have one dominant and one recessive the trait
shown will be the dominant. If you have two recessive alleles the trait shown will be the
recessive trait. )
o Gene- a segment of DNA that codes for a specific protein, the protein which is made
will produce the desired characteristic.
o Allele- Every characteristic has multiple possibilities, for example eye color in
humans has several variations. These different gene types are called alleles. The
definition for allele is different variations of the same gene.
o Dominant gene- Is a gene / trait that is represented with an upper case letter (T).
This trait will always show its characteristics over recessive traits.
o Recessive trait- Is a gene / trait that is represented with a lower case letter (t). This
trait will only show its characteristic if there is an absence of the dominant trait.
o Co-dominant trait- Both genes controlling the trait are dominant. The results of a
co-dominant trait show both characteristics of each gene. Ex. A dominant white
allele + a dominant black allele will result in a spotted of speckled black and white
trait.
o Sex-linked genes- Are genes found on the X or Y chromosome. Because these sex
linked chromosomes get separated differently during meiosis, they show different
results when doing a genetic cross. The male of the species contains only one X
chromosome and a single Y chromosome. Since the male only contains one X
whatever allele is on the X chromosome will show. Autosomes are chromosomes
that are not sex chromosomes.
o Incomplete dominance- Is when neither allele is completely dominant over the
other and it results is a mix of the two genes. Ex. Dominant white allele+ Dominant
red allele will result in a pink, which is a blending of the two genes.
 Genotype- Is a term used to describe the types of genes present. There are
3 different genotypes: Homozygous dominant, homozygous recessive, and
Heterozygous.
 Homozygous Dominant- Remember that the prefix homo means
the same. Homozygous dominant means there are two dominant
alleles present. Ex. (TT)
 Homozygous recessive- Means there are two recessive alleles
present. Ex. (tt)
 Heterozygous- Hetero literally means different. Heterozygous
means 2 different alleles, one dominant and one recessive. Ex. (Tt)
o Phenotype- Is a word used to describe the physical characteristic of a gene.
o
An example of a Punnett square.
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