BI30-GB3 Investigate the storage, transmission, and expression of genetic information at the
molecular level.
a. Assess the importance of the structure of the DNA molecule to its capacity for storage, transmission,
and expression of genetic information. (K)
b. Discuss the contributions of various scientists (e.g., Chargaff, Franklin, Wilkins, Watson, and Crick) to
understanding the structure of DNA. (K, STSE)
f. Explain molecular genetic processes of DNA replication and protein synthesis, including the roles of
DNA, mRNA, tRNA and rRNA. (K)
g. Model molecular genetic processes, including DNA replication, transcription, and translation. (S)
Nucleic Acids
Central Dogma – DNA to RNA Video (first video is suggested!)
http://www.bozemanscience.com/science-videos/2012/5/6/transcription-and-translation.html
The Structure of DNA
Chargaff analyzed the amounts of the four nucleotides found in DNA (Adenine, Thymine, Guanine,
Cytosine) and noticed a pattern.
1. The amount of A, T, G, C varies from species to species
2. In each species, the amount of A = T, and the amount of G = C ---- Base Pair Rule
Bases come in two types: pyrimidines (cytosine and thymine) and purines (guanine and adenine)
Rosalind Franklin and Wilkins spent time taking X-ray diffraction pictures of the DNA molecule in an
attempt to determine the shape of the DNA molecule.
Watson and Crick are credited with finally piecing together all the
information previously gathered on the molecule of DNA. They
established the structure as a double helix - like a ladder that is
twisted. The two sides of the ladder are held together by hydrogen
bonds.
Watson & Crick Model of DNA
The sugar (deoxyribose) and phosphates make up the "backbone" of
the DNA molecule.
The phosphate is attached to the 5' carbon (the 5 is a number given to
sugar molecules). The DNA strand has a free phosphate on th 5' end,
and a free sugar on the 3' end - these numbers will become important later.
Adenine always pairs with Thymine | Guanine always pairs with Cytosine
Side1:: A A T T G G C C A G A T A C
Side2:: T T A A C C G G T C T A T G
DNA is composed of subunits called nucleotides, strung together in a long chain -- Each nucleotide
consists of: a phosphate, a sugar (deoxyribose), and a base
More Images:
This DNA molecule is not represented well. What is wrong with it?
(answer: the sugar molecules are not antiparallel ^)
Here the 5' end and the 3' end are seen again, each side of the ladder has an opposite orientation. One
side of the ladder as a free sugar (the 3'end) the other side has a free phosphate (the 5'end). This
arrangement is called: ANTI-PARALLEL
DNA Replication
http://www.biologycorner.com/APbiology/DNA/13-3_replication.html
-the process by which DNA makes a copy of itself
-occurs during interphase, prior to cell division
Steps of DNA replication
1. DNA helicase (enzyme) unwinds the DNA. The junction is called
a replication fork.
2. DNA polymerase adds the complementary nucleotides and binds the
sugars and phosphates. DNA polymerase travels from the 3' to the 5'
end. The DNA is called the template strand.
3. DNA polymerase adds complementary nucleotides on the other side of the
ladder. Traveling in the opposite direction.
4. One side is the leading strand - it follows the helicase as it unwinds.
5. The other side is the lagging strand - its moving away from the helicase (in
the 5' to 3' direction).
Replication is called semi-conservative, because one half of the original
strand is always saved, or "conserved"
Problem: it reaches the replication fork, but the helicase is moving in the
opposite direction. It stops, and another polymerase binds farther down the
chain.
This process creates several fragments, called Okazaki Fragments, that are
bound together by DNA ligase.
6. During replication, there are many points along the DNA that are
synthesized at the same time (multiple replication forks). It would take forever
to go from one end to the other, it is more efficient to open up several points at
one time.
Replication Errors – can cause a genetic MUTATION
-- PROOFREADING by the polymerase prevents mismatches
-- DNA REPAIR ENZYMES can repair damaged DNA also
Additional Resources
Animation of Replication (stolaf.edu)
Animations of Replication (mcgraw-hill)
Replication Tutorial (wiley.com)
Replication Fork (mcb.harvard.edu)
Please complete DNA Coloring - Transcription & Translation, and DNA Molecule of Heredity
Worksheet.
DNA Building Assignment
Your Job:
� to recreate a DNA molecule with the material of your
choice.
� You may decide on the DNA base pairing code
� You must include a legend that explains what each aspect
is represented by
You Need to Include:
� the Nitrogen Bases (Adenine, Thymine, Guanine and
Cytosine)
� the Hydrogen bonds
� the Phosphate molecules
� the pentose (5-C sugar)
The Requirements:
� must have at least 10 pairings
DNA Building Assignment Evaluation
Names: _________________ Mark:___________
Model has:
_____ Phosphate Molecules (1)
_____ Pentose Sugar (1)
_____ Nitrogen Bases ( A-T and G-C) (2)
_____ Hydrogen Bonds (1)
_____ Has at least 10 pairings (1)
_____ Clearly labeled legend (2 marks)
TOTAL = 8
c. Recognize various types of gene mutations (e.g., deletion, insertion, point, and frameshift) and how
they may lead to genetic disorders. (K)
http://highered.mheducation.com/sites/9834092339/student_view0/chapter15/addition_and_deletion
_mutations.html
d. Discuss the mechanisms of DNA proofreading and repair. (K)
http://highered.mheducation.com/sites/9834092339/student_view0/chapter14/proofreading_function
_of_dna_polymerase.html
e. Assess the role of genetic mutation in the process of evolution. (K)
Do you think all mutations are bad for us?
h. Investigate factors (e.g., environmental, epigenetic, and homeobox [Hox]) that control genetic
expression. (K)
http://www.biologycorner.com/APbiology/DNA/15_mutations.html
Regulation of Gene Activity
Prokaryote Regulation
Experiments with E. Coli showed that it is capable of regulating the expression of its genes
An operon consists of the following elements
1. Promoter - where RNA polymerase attaches, signalling the start of the gene
2. Operator - where repressor binds, stopping the transcription of that gene
3. Structural Genes - code for an enzyme, transcribed as a unit
Example: the trp Operon controls the production of tryptophan
Tying it altogether - the Lac Operon Gene
E. Coli bacteria can synthesize lactase, which is an enzyme that breaks down lactose. Lactase
is only synthesized in the presence of lactose. If there is no lactose in the environment, the gene
is repressed. Since they live in the intestinal tract of humans, they must live on whatever the
host eats. When you drink milk, you are provided your E. Coli bacteria with lactose.
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E. Coli has three genes (6, 7, 8) that code for lactase.
It also has a promoter (1) and an operator (2)
Without lactose, the lac repressor binds to the operator site.
With lactose (5), the repressor is removed
Once repressor is removed, RNA polymerase binds to the promoter
RNA is transcribed, the genes (6,7,8) code for lactase
Repressors turn transcription OFF(tryp operon)
Inducers turn transcription ON (lac operon)
Eukaryote Regulation
In Eukaryotes, a variety of mechanisms regulate gene expression
1. chromatin structure
2. transcriptional control (operons)
3. post transcriptional control
4. translationslation control
5. post translational control
Chromatin Structure
DNA is wound around a core of eight protein molecules, the result resembles beads on a string.
The protein molecules are histones and each individual bead is called a nucleosome
Barr Bodies
Females have two X chromosomes, but it is believed that one of the inactivates. The expression
of the genes located on the X chromosome depends on which X is active (random).
Calico cats have the patchwork color because the genes for black and orange colors are
located on the X chromosome
Photo Credit: deadoll via Compfight cc
15.3 Gene Mutations
Point Mutation - substitute one base for another
Original: A T A C A C
Mutant : T T A C A C
Frameshift Mutation - a base is either added or removed which causes a shift in the reading
frame. Many genes affects
Original: A T A C A C A A G C C A
Mutant: A T T A C A C A A G C C A
Silent Mutation - a base is changed but the resulting amino acid is the same as in the non
mutant DNA. No outward changes.
Original: A A A C A G
Mutant: A A G C A G
Nonsense Mutation - a codon is changed to a STOP codon
Original: A T A C C C A A A
Mutant: A T T C C C A A A
Cancer
often results from a mutation in a TUMOR SUPPRESSOR GENE
Oncogenes activate causing uncontrollable cell division.
The BRCA (brak-uh) gene has been identified as the gene responsible for one type of breast
cancer, it is located on Chromosome 17
Transposons
- Jumping Gene, a stretch of DNA that inserts itself into a different spot on a chromsome or
another chromosome
*Mutations in DNA can cause a change in species --> Evolution
*HOX mutations can cause major changes in morphology
Epigenetics
See Learn.Genetics article
Genes become activated or inactived based on environmental triggers. These triggers may
have occurred in previous generations.
Methyl is responsible for turning genes on an off (methylation)
The Homeobox
Homeobox containing, or "hox," genes are responsible for the big decisions of development
rather than the details of engineering.
Fruit flies with a particular mutation in one of their many hox genes, for example, will develop an
anatomically normal leg - in the spot where an antenna should be.
This mutation can also duplicate segments of the body, resulting in flies that have a double set
of wings. (See Gallery of Drosophila Mutants)
i. Model or simulate the techniques (e.g., agarose gel electrophoresis, polymerase chain reaction, and
DNA sequencing) used by molecular geneticists. (S, K, A, STSE)
j. Appraise the importance of understanding the structure of DNA to advances in various fields of
biology. (A, K, STSE)
k. Provide examples of current and emerging biotechnologies (e.g., recombinant DNA, genetic testing
and screening, gene therapy, stem cells, and cloning). (K)
http://www.biologycorner.com/APbiology/DNA/16_biotechnology_cloning.html
Biotechnology
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Recombinant DNA Technology
Gene Sequencing (Human Genome Project)
Cloning
Stem Cell Research
Gene Therapy
DNA Fingerprinting (and other Forensics applications)
DNA Cloning
Cloning is the production of identical copies of DNA
1. Stems or root send up new shoots that are clones of the parent plant.
2. Members of a bacterial colony on a petri dish are clones because they
all came from division of the same cell.
3. Human identical twins are clones; the original single embryo separate to
become two individuals. (Artificial Twinning)
4. Somatic Cell Nuclear Transfer (SCNT) – adult cells used to create an
embryo
Gene cloning is production of many identical copies of the same gene.
1. If the inserted gene is replicated and expressed, we can recover the
cloned gene or protein product.
2. Cloned genes have many research purposes: determining the base
sequence between normal and mutated genes, altering the phenotype,
obtaining the protein coded by a specific gene, etc.
3. Humans can be treated with gene therapy: alteration of the phenotype
in a beneficial way.
Recombinant DNA Technology
1. Recombinant DNA (rDNA) contains DNA from two or more different
sources.
2. To make rDNA, technician selects a vector.
3. A vector is a plasmid or a virus used to transfer foreign genetic material
into a cell.
4. A plasmid is a small accessory ring of DNA in the cytoplasm of some
bacteria.
5. Plasmids were discovered in research on reproduction of intestinal
bacteriaEscherichia coli.
6. Introduction of foreign DNA into vector DNA to produce rDNA requires
two enzymes.
a. Restriction enzyme is a bacterial enzyme that cuts DNA, it creates
fragments of DNA with “sticky ends”
b. DNA ligase joins fragments together
The Polymerase Chain Reaction
1. PCR can create millions of copies of a single gene or a specific piece of
DNA in a test tube.
2. The polymerase chain reaction (PCR) uses the enzyme DNA polymerase to
carry out multiple replications (a chain reaction) of
target DNA.
Analyzing DNA Segments
1. Mitochondria DNA sequences in modern living populations can decipher
the evolutionary history of human populations.
2. DNA fingerprinting is the technique of using DNA fragment lengths,
resulting from restriction enzyme cleavage and amplified by PCR, to identify
particular individuals.
a. DNA is treated with restriction enzymes to cut it into different sized
fragments.
b. During gel electrophoresis, fragments separate according to length,
resulting in a pattern of bands.
c. DNA fingerprinting can identify deceased individuals or perpetrators of
crimes
3. PCR amplification and DNA analysis is used to:
a. detect viral infections, genetic disorders, and cancer;
b. determine the nucleotide sequence of human genes: the Human Genome
Project; and
c. associate samples with DNA of parents because it is inherited.
Biotechnology Products
1. Genetically engineered organisms can produce biotechnology products.
2. Organisms that have had a foreign gene inserted into them
are transgenic.
A.
Transgenic Bacteria
1. Bacteria are grown in large vats where they can make products such as
insulin and human growth hormone, and vaccines
2. Transgenic bacteria have been produced to improve the health of plants
and degrade substances, such as oil
3. Transgenic bacteria can produce chemical products, such as phenylalanine
(artificial sweeteners)
B. Transgenic Plants
1. Foreign genes now give cotton, corn, and potato strains the ability to
produce insect toxin s
2. Plants are being engineered to produce human proteins including
hormones, clotting factors, and antibodies
C.
Transgenic Animals
Animal use requires methods to insert genes into eggs of animals (early in
development). Using this technique, many types of animal eggs have been
injected with bovine growth hormone (bGH) to produce larger fishes, cows,
pigs, rabbits, and sheep.
“Gene pharming” is the use of transgenic farm animals to produce
pharmaceuticals; the product is obtainable from the milk of females.
D.
Cloning Transgenic Animals
1. The cloning of Dolly in 1997 showed that mammals could be cloned.
2. Cloning of mammals involves injecting the nucleus of an adult cell into an
enucleated egg.
3. The cloned eggs begin development in vitro and are then returned to host
mothers until the clones are born.
Scenario 1: A well-loved horse named Barbero breaks his leg in a
race. Many people were praying for his well being and thousands of dollars
were spent trying to get him to recover. Mail and flowers poured into the
animal hospital and stable where Barbero lived. Alas, after a year of poor
recovery, the decision was made to euthanize Barbero. The owners save
sample of his DNA so that Barbero can be cloned. Do you think they should
clone him? Why or why not.
Scenario 2: Melissa is a happy 5 year old who is loved by her family. She
becomes ill and is diagnosed with childhood leukemia. A desperate search
ensues to find a bone marrow donor whose type matches Melissa. After a
year of searching, Melissa’s outlook is grim. Her family decides to clone
Melissa so that her clone could be the bone marrow donor. Do you think this
is a god idea? Why or why not.
Genomics
Genetics in the 21st century concerns genomics: the study of genomes of
humans and other organisms.
A. Sequencing the Bases
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The Human Genome Project has produced a working draft of all the
base pairs in all our chromosomes.
The task took 13 years to learn the sequence of the three billion base
pairs along the length of our chromosomes.
Other organisms are being sequenced to compare genes and located
genes responsible for disorders.
The HapMap Project
in humans.
-- catalogs sequence differences, called haplotypes,
The Genetic Profile
1. DNA microarrays identify a person’s complete genotype; this is called
the genetic profile.
2. DNA profiles can determine if a person has an increased risk for a
particular disease
3. The genetic profile can be used to determine if a particular drug therapy
is appropriate in a specific clinical condition.
Proteomics
1. Proteomics is the study of the structure, function, and interaction of
cellular proteins.
2. The information obtained from proteomic studies can be used in
designing better drugs, and to correlate drug treatment to the particular
genome of the individual.
Bioinformatics
1. Bioinformatics is the application of computer technologics to the study
of the genome.
2. Information obtained from computer analysis of the genome can show
relationships between genetic profiles and genetic disorders.
Gene Therapy
1. Gene therapy involves procedures to give patients healthy genes to
make up for a faulty gene.
2. Gene therapy also includes the use of genes to treat genetic disorders
and various human illnesses.
3. There are ex vivo (outside body) and in vivo (inside body) methods of
gene therapy.
Please complete The Quest to Resurrect Extinct Species, Genetic Engineering Concept Map.