Science Study Guide
Chapter 8 – INSTRUCTIONS FOR LIFE
KEY CONCEPTS
AND
VOCABULARY
Learning Log – Your Learning Log, which is your “test aid” should contain the
following PRIMARY CONCEPTS along with the VOCABULARY WORDS that you will
need to explain your understanding of each concept.
CONCEPT 1 – DNA is found in all living things and carries the genetic code for their
characteristics.
DNA is found in the nucleus of all plant and animal cells and therefore, DNA is found in all
living things. DNA consists of a string of molecules called Nucleotides and it is these
nucleotides that provide the codes for making Proteins. The Proteins that cells make
determine the characteristics of all organisms.
There are four types of nucleotides in all DNA strands. They are: Cytosine, Guanine,
Thymine and Adenine. They are typically identified using the First Letter of each of the
Nucleotides, C, G, T and A.
The Sequence of these Nucleotides in each DNA strand provides the Code for making the
proteins that determine the traits or characteristics of all living organisms.
CONCEPT 2 – DNA can replicate to pass its genetic information to newly formed cells.
DNA carries the code for making Proteins that determine the characteristics of all living
organisms. This Code must be present in every cell in an organism. In order to get this code
in every cell, DNA must be able to Copy Itself. This process is called REPLICATION.
Replication is important for TWO REASONS: 1. Replication during the Meiosis process
creates Gametes, which are new cells containing half the genetic information of the parent and
will combine with gametes from a parent of the opposite sex to create offspring … AND…, 2.
Replication during Mitosis generates complete NEW CELLS within each organism for
growth and maintenance.
The Replication process must accurately copy each DNA strand to insure each new cell
contains the correct code for making proteins that determine the characteristics of the
organism. Failure to replicate properly could result in cells that are not able to produce the
proteins necessary for reproduction, growth or maintenance of an organism.
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How Does Replication Happen?
Complete DNA molecules consist of TWO Strands that form a Double Helix. The strands are
connected to each other by Hydrogen Bonds.
The Nucleotides in one strand of the “helix” are only able to bond with one type of
nucleotide in the other strand of the helix, this is called “complimentary base pairing”. The
Adenine, or “A” nucleotide can only bond with the Thymine, or “T” nucleotide. The Cytosine,
or “C” nucleotide can only bond with the Guanine, or “G” nucleotide.
During the Replication process, the Hydrogen Bond that connects the two DNA strands into
the Double Helix is broken and the two DNA strands separate creating Two Templates that
will form into new Double Helix DNA strands. Due to “Complimentary Base Pairing” that will
only allow an “A” nucleotide to bond with a “T” nucleotide and a “G” nucleotide to bond with a
“C” nucleotide, the new strands that form and bond to the separated template strands will
result in two new double strands that are IDENTICAL to the ORIGINAL Double Strand
before it separated and started the replication process.
In summary, the replication process insures that each new double strand of DNA will contain
the same code for making the proteins that determine the characteristics of the organism.
This insures that the new cells will be able to provide for growth and maintenance of the
organism and that the characteristics of the organism are passed along to their offspring
through gametes.
CONCEPT 3 – DNA serves as a template for making proteins.
The sequence of the nucleotides in a DNA Strand form a Code that will lead to the
production of Proteins. The production of proteins is also known as Protein Synthesis. With
just 4 different nucleotides, DNA can provide codes for the production of hundreds of
thousands of different proteins. These proteins will determine the characteristics of the
organism.
A DNA sequence that provides the Code to make a particular protein is a GENE. There may
be thousands of protein codes, thus thousands of GENES in a single DNA strand. For this
reason, DNA is often referred to as Genetic Code or is said to Contain Genetic Code.
DNA strands, which provide the Code for making proteins, are solely contained in the
nucleus of cells. Proteins are produced outside of the nucleus, in an area of the cell called
the Ribosome. The code carried in the DNA strand must be transferred from the nucleus of
cells to the Ribosome before proteins can be made. RNA molecules provide the means of
transferring the Code from the DNA strands to the area of the cell outside the nucleus
where the proteins are actually made. Each DNA strand serves as a TEMPLATE from
which RNA molecules are made. The RNA molecules copy the Code from the DNA strand
and transfer the Code to an area of the cell where proteins can be manufactured.
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In Summary, the DNA contains the code for making the proteins that determine the
characteristics of an organism. However, DNA exists only in the nucleus of cells and proteins
are made in an area of the cell that is outside the nucleus. The code to make proteins is
transferred out of the nucleus by RNA molecules that use the DNA strand as a TEMPLATE
to copy the code and transfer it to the area of the cell where the proteins are actually
made.
CONCEPT 4 – Proteins are substances essential to life.
Proteins are responsible for virtually everything that makes up all organisms, both plant and
animal. Proteins, which make up a large part of all living cells, determine the
characteristics of organisms and allow all organisms to function, grow, heal, survive and
reproduce.
There are literally hundreds of thousands of different proteins that combine to create the
characteristics of all organisms and then sustain those organisms in life. All proteins have a
specific function but many proteins may provide similar functions as a group. Different
classifications of proteins include:
Catalysts – Proteins that speed up chemical reactions
Nutrients – Proteins that support growth and maintain overall general health
Storage – Proteins that create fats and build muscles
Contractive – Proteins that facilitate movement
Defensive – Proteins that support the immune system
Regulatory – Proteins that maintains body chemistry, such as glucose levels
Structural – Proteins that generate or replenish structural matter such as skin, bones, hair,
Muscles, tissue, nails, etc.
Other “Unique” Proteins that serve a single specific function in maintaining life or health
CONCEPT 5 – Mutations in DNA result in changes in proteins that can be advantageous,
detrimental, or neutral (have no effect) to individual organisms and their species.
DNA replication, transcription and translation are occurring in the cells of living organisms
every second of every day. Most of the time, these processes occur without any problems
and the Gametes that result from Meiosis or the complete new cells that result from Mitosis are
identical copies of the genetic information contained in the “parent” cells.
However, with the volume of replications that are occurring continuously, mistakes can and do
happen and these mistakes result in cells that contain DIFFERENT DNA CODE SEQUENCES
than the parent cells. These mistakes are called MUTATIONS.
Mutations can result from mistakes during the replication, transcription and translations
processes and they can also result from other natural factors such as exposure of cells to
radiation or other environmental factors such as chemical toxins that exist in cigarette smoke
or toxic wastes that may be released into the environment.
(Continued on next page)
Once a mutation in the DNA CODE SEQUENCE has occurred, this mutation will be present
in all future cells that replicate from the mutated cell. This results in a group of mutated cells
within an organism which may, or may not affect that organism. Cancer is an example of
mutated cells that rapidly and continuously grow into a large group of mutated cells that have
definite adverse effects on the health of the organism.
Mutations that occur during the replication process of Meiosis will result in gametes that
contain the mutation and can therefore be passed along to offspring. These mutations
add to the potential for variation in the species and can also lead to the evolution of a new
species when the mutation actually helps the offspring to survive in a particular environment.
For example, a mutation that resulted in an offspring having longer claws might help that
offspring catch food and survive more easily than offspring who do not have the mutation. This
would increase the probability that the mutated offspring would live to reproduce and pass the
longer claws gene on to its offspring. This demonstrates how natural selection leads to
evolution of a species that is more adapted to its environment.
In Summary, mutations occur frequently. In fact, complex organisms, such as humans, may
contain many mutations in their cells. Some mutations may be caught and corrected by
naturally occurring protective proteins within the organism while other mutations may have no
adverse effects on the organism. Mutations that occur during MITOSIS only affect the
individual who has the mutated cells. Mutations that occur during the MEIOSIS process
result in gametes with mutations and these can be passed along to offspring. Mutations in
offspring can simply result in minor differences between the parent and offspring, or, they
can result in potentially deadly genetic diseases, or even new traits that might support
evolution of the species through natural selection. A favorable mutated trait that improves
the survival of the offspring over time, allows that favorable trait to be passed along from
generation to generation may result in the evolution of the species into a new species
with the improved trait.
CONCEPT 6 – Similarities in DNA show relatedness of organisms.
Advances in DNA technology now allow scientists to determine the DNA sequences in
organisms. These DNA sequences give scientists a great deal of information about
organisms and how they may have evolved over time.
DNA sequences can be used to determine how closely related organisms are. The more
Base Pair Similarities organisms have in a selected DNA sequence, the more closely related
the two organisms are.
Scientists can use the comparisons of Base Pair similarities to help develop theories about
ancestral lines and other evolutionary relationships.
VOCABULARY (in alpha order)
Amino Acids – The basic building blocks that make proteins. Chains of 3 Amino Acid
molecules, which are sequenced by tRNA Anticodons, create specific Amino Acids and these
Amino Acids combine to make the proteins that are vital in sustaining all aspects of life.
Complimentary Base Pairing – The natural pairing of nucleotides when they bond to form the
dual strand helix that makes up every complete DNA molecule. During this natural pairing
process, Cytosine ALWAYS bonds with Guanine and Adenine ALWAYS bonds with Thymine.
Enzymes – A special type of protein that speeds up reactions, enzymes are often referred to as
“catalysts”.
DNA – (deoxyribonucleic acid) – The molecules within a chromosome where genetic
information of an organism is stored in the form of genetic coding. DNA coding provides
the template for making all proteins that determine the characteristics of all living organisms and
provide for the survival and reproduction of all living organisms.
Gene – A DNA sequence of nucleotides that codes for a protein.
Nucleotides – Special nitrogen based molecules that make up the DNA Strands. There are
FOUR types of nucleotides, Adenine, Cytosine, Guanine, and Thymine, often referred to by the
Code Letters “A”, “C”, “G”, and “T”. There are BILLIONS of nucleotides in the cells of every
organism.
Mitosis – The entire process involved in producing new cells in all living organisms. The
process begins with DNA Replication and is followed by a cell division that results in TWO
Daughter Cells that are IDENTICAL to the original Parent Cell. Mitosis is vital to all living
organisms because new cells are continuously needed to facilitate growth and maintenance of
the organism.
Mutations – Changes that occur in the DNA Code due to mistakes that happen during the
Replication process, or due to environmental influences on cells such as radiation or exposure
to chemical toxins. Mutations that occur during MITOSIS remain within the effected organism.
Mutations that occur during MEIOSIS can be passed along to offspring. Mutations can be
advantageous, neutral (have no effect), or detrimental to organisms.
Proteins – Long chains of Amino Acids held together by covalent bonds. Proteins differ from
each other by the sequence and number of amino acids in each chain. The sequence of the
amino acids determines the function of the protein. Proteins are responsible for facilitating most
chemical reactions in organisms and are grouped in classifications based on the functions of the
proteins. Classifications include: Structural, Nutritional, Storage, Contractile, Defensive,
Regulatory, and other unique specialty proteins. In Humans, there are over 50,000 different
proteins, each with a different function. Proteins determine all inherited traits, provide for growth,
maintenance, immunity, healing, and all other vital life functions.
Replication – The process in which DNA makes a copy of itself. Replication is a VITAL STEP
in the MEIOSIS process that produces gametes for sexual reproduction AND in the MITOSIS
process that creates new cells that allow for growth and maintenance of all living organisms.
Ribosome – Area of a cell where Proteins are actually made
RNA – A single strand of Nucleotides that is similar to DNA. There are Three Types of RNA and
all three are necessary in the process of making proteins.
mRNA – Messenger RNA – A single strand of nucleotides created by copying the code
from one strand of DNA. mRNA follows the same “Complimentary Base Pairing” as the
replication process with the EXCEPTION of the nucleotide Uracil replacing Thymine in
the pairing process that creates the mRNA strand. mRNA carries the genetic Code from
the DNA out of the nucleus of the cell and to an area of the cell where proteins are
made.
rRNA – Ribosomal RNA - rRNA interprets the Code carried in the mRNA strand into
sections of Three Nucleotides. These sections are called CODONS.
tRNA – Transfer RNA – tRNA is a COMPLIMENTARY Section to each Codon section
interpreted during the rRNA process. These COMPLIMENTARY sections are called
ANTICODONS. The tRNA sections pick up Amino Acids from the Cytoplasm area of
the cell and assembles them into AMINO ACID CHAINS that MAKE THE SPECIFIC
PROTEIN THAT IS CODED by the nucleotides in the tRNA section.
SEE EXAMPLE ON THE FOLLOWING PAGE
DETAILING THE PROTEIN PRODUCTION PROCESS
Transcription – The copying of ONE DNA strand to make RNA. This is the First Step in the
process of producing Proteins. The Single Strand of RNA that results from Transcription is
called mRNA, (Messenger RNA), and it carries the DNA Code out of the Cell nucleus and to the
Ribosome of the cell where proteins are made.
Translation – The process of reading the code on the mRNA strand and using that code to
make rRNA codons, which in turn make tRNA Anticodons that pick up amino acids from the
cytoplasm of the cell and form them into Amino Acid Chains which ultimately result in the
production of Proteins
“HOW ORGANISMS MAKE PROTEINS”
DNA in the cell nucleus provides a TEMPLATE for RNA Strands. RNA strands carry the DNA
code out of the nucleus of the cell to the RIBOSOME where proteins are actually made. The
RNA process that produces proteins is detailed in the example below.
Reminder about “Complimentary Pairing” in the RNA process
** U replaces T in the RNA Complementary Pairing Process
U always pairs with A, and A always pairs with U
C always pairs with G, and G always pairs with C
START – Reference the following sample “section” of DNA
TACGCA
First Step – Transcription of Code from DNA strand to new mRNA strand
NEW mRNA Strand - A U G C G U
Second Step – Translation of mRNA into rRNA – Code is “interpreted” into sections of
three nucleotides each, these sections are called Codons
rRNA Codons interpreted from mRNA - A U G and C G U
Third Step – Translation of rRNA into tRNA – COMPLIMENTARY sections of nucleotides
are created from the rRNA code, these complimentary sections are called Anticodons.
tRNA Anticodons copied from rRNA - U A C and G C A
Final Step – Proteins are produced according to the CODE contained in the Anticodons
The Anticodons pull Amino Acids together from the ribosome area of the cell to form
chains according to the code contained in the Anticodon. Each different Code causes a
specific type of Amino Acid to be produced. In this example, Code UAC will produce
the Amino Acid Cysteine and the Code GCA will produce the Amino Acid Alanine.
Coded groups of Amino Acids, which correspond to a single genetic code in the
DNA, combine to make a specific protein. These proteins will determine the
characteristics of organisms, create their structure, and support their growth and
maintenance. Essentially, DNA codes provide the roadmap for the production off all
proteins which in turn create and support all living organisms.
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