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 How did Morgan’s research build upon Mendel’s
observations?
 Morgan used dihybrid crosses in fruit flies to study
a new pattern of inheritance that revealed gene
linkage in phenotypes.
 His results did not always follow Mendel’s 9:3:3:1
pattern.
 The probability that two genes on a chromosome
will be inherited together is related to the_______
between them.
 distance
 Maps of the relative locations, or loci, of genes on a
chromosome.
 Linkage maps
 What scientist discovered linkage maps? When?
 Alfred Sturtevant, 1913
 How can a linkage map be made from observations
of traits?
 By calculating the percentage of times phenotypes
do not appear together in offspring of parents with
known genotypes.
 Summarize the importance of comparing wild type
and mutant type fruit flies in genetic research.
 The different types of flies were important in
determining gene linkage because the different
phenotypes were easily observed.
 How is a linkage map related to cross-overs that
take place during meiosis?
 The higher the frequency of two genes crossing
over separately, the farther they are from each other
on a chromosome.
 How are linked genes similar to sex-linked genes?
How are they different?
 Similar because both show a pattern of linkage in
inheritance.
 Different because linked genes are linked to each
other on the same chromosome whereas sex-linked
genes are linked to either the x or y chromosome
 How can carriers differ between autosomal and sex-
linked disorders?
 Only females can be carriers of sex-linked disorders.
 A chart that can help trace the phenotypes and
genotypes in a family to determine whether people
carry recessive alleles.
 A pedigree chart
 If approximately the same number of males and
females have the same phenotype, then the gene is
most likely on an _________.
 autosome
 If a phenotype is much more common in males the
gene is likely on the ________ chromosome.
 X
 How are Pedigrees and Punnett squares different?
 Punnett squares predict offspring phenotypes from
known genotypes.
 Pedigrees predict genotypes from phenotypes.
 Punnett squares show a predicted outcome where
Pedigrees show an actual outcome.
 A picture of all of the chromosomes in a cell.
 Karyotype.
 Why must many methods be used to study human
genetics?
 The human genome is huge…. Well…. Incredibly
small….. But very complex.
 How can Mendel’s principles be used to study human
traits?
 They apply to autosomal single-gene traits with
dominant and recessive patterns in all sexually
reproducing organisms.
 Is a person who is homozygous recessive for a recessive
genetic disease a carrier?
 No, A carrier is someone who has a gene for the
disorder but does not display the phenotype.
 Suppose a colorblind male and a female with no
recessive alleles for colorblindness have children. What
is the probability they will have a colorblind son? A
colorblind daughter?
 Zero. Any son will inherit the normal allele from his
mother.
 Any daughter will have a normal phenotype but will be
a carrier.
 Under what circumstances could two individuals
with no symptoms of a recessive genetic disease
have children that do have the disease?
 If the disorder is autosomal, both parents must be
carriers (heterozygous). If the disorder is sexlinked, the mother must be a carrier.
 Can a person merely be a carrier for a dominant
genetic disorder?
 No. If a person has just one allele for a dominant trait,
that trait will be expressed.
 Both men and women can be colorblind, but there are
approximately 100 times more colorblind men than
women in the world. Explain why men are more likely
to be colorblind than women.
 If a male has a recessive allele of a sex-linked gene, the
allele is always expressed because males have only one
X chromosome.
 Females have 2 X Chromosomes and must have two
copies of a recessive allele to express the trait.
 Why are studies of identical twins important in
helping understand interactions between
environment and genotype?
 Identical twins have the same genotype.
 Phenotype differences must be studied in
connection with environmental differences.
 In 1928, Frederick Griffith was studying two forms of
the bacterium that causes pneumonia. Describe the
observable differences between the bacteria.
 One form was surrounded by a coating of sugar
molecules. He called these S because of their smooth
appearance.
 The second form had a rough outer appearance, so he
called it R.
 If Griffith’s 1982 experiment on pneumonia causing
bacteria, which form killed the mice.
 The S or smooth form.
 In Griffith’s 1928 experiment, how did heat-killed S
form bacteria affect the mice?
 The mice survived.
 In Griffith’s 1928 experiment, what happened to mice
when they were injected with live R bacteria?
 They survived.
 In Griffith’s 1928 experiment, what happened to the
mice that were injected with heat-killed S bacteria and
live R bacteria?
 The mice died.
 In Griffith’s 1928 experiment, when mice were injected
with live R bacteria they survived. When they were
injected with heat-killed S bacteria, they survived.
When mice were injected with both, they died. Why?
 Some material (DNA) must have been transferred
from the heat-killed S bacteria to the live R bacteria.
The once harmless R bacteria was changed into a
harmful form of bacteria. This became known as ‘the
transforming principle’.
 From 1934 to 1944, what was Oswald Avery and his
team trying to determine?
 They were trying determine if the transforming
principle was casual by DNA or protein.
 In 1944, when Avery and his team presented their
evidence that DNA caused the transforming
principle, why did some scientists continue to
harbor doubts?
 Some scientists insisted that his extract must have
contained protein.
 In 1944, what evidence did Oswald Avery and his team
present that pointed to DNA as causing the
transforming principle?
 1.) Standard tests showed that DNA was present in
their extract but not protein.
 2.) A chemical analysis showed that the proportions of
elements in the extract modeled DNA.
 3.) Transformations failed to occur when an enzyme
was added to destroy DNA.
 What is a bacteriaophage and what does it do?
 It is a type of virus.
 It takes over a bacterium's genetic machinery and
directs it to make more viruses.
 What is an elemental difference between
protein and DNA? How did Hershey and Chase
make use of this difference?
 Protein contains sulfur but little phosphorus
 DNA contains phosphorus but no sulfur
 They radioactively tagged phages in cultures
with sulfur or phosphorus.
 Describe Hershey and Chase’s first experiment over the
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transforming principle.
Bacteria was infected with phages that had radioactive
sulfur atoms in their protein molecules.
They then separated the bacteria from the phages that
were outside of the bacteria. (The phages would have
injected material into the bacteria.)
After examining the bacteria, no significant
radioactivity was found.
This meant that the bacteriophage was not injecting
protein into the bacteria to make copies of itself.
 Describe Hershey and Chase’s second
experiment over the transforming principles.
 They tagged the phages’ DNA with radioactive
phosphorus.
 Radioactivity was clearly present in bacteria.
 Their findings proved that genetic material is
DNA, and not protein. (Proven in 1952)
 DNA is composed of four types of _________.
 Nucleotides
 The small units, or monomers, that make up DNA are
called __________.
 Nucleotides.
 What are the three parts of a nucleotide?
 A phosphate group, A ring-shaped sugar called
deoxyribose, and a nitrogen containing base.
 How do nucleotides differ from one another?
 Only in their nitrogen-containing bases.
 What are the four bases of DNA?
 Cytosine
 Thymine
 Adenine
 Guanine
 What hypothesis was the key reason that scientists
were not convinced that DNA could be genetic
material?
 Scientists hypothesized that DNA was made up of
equal amounts of the four nucleotides.
 This means that the DNA in all organisms would be
exactly the same. Identical molecules could not carry
out different instructions across all organisms.
 In 1950, how did Erwin Chargoff change how scientists
viewed DNA?
 He found that the proportion of the four nitrogen
bases differs from organism to organism.
 Describe Chargoff’s rule.
 The amount of cytosine roughly equals the amount of
guanine.
 The amount of adenine roughly equals the amount of
thymine.
 What did Watson and Crick develop and present in
1953?
 An accurate model of DNA’s 3D structure.
 The double helix model. It also explained
Chargoff’s rule by showing how Cytosine combines
with guanine and adenine combines with thymine.
 What type of bond holds the DNA helix together
between the bases in the middle?
 A hydrogen bond.
 What type of bond connects the sugar of one
nucleotide to the phosphate of the next nucleotide?
 A covalent bond.
 Which part of a DNA molecule carries the genetic
instructions that are unique for each individual: the
sugar-phosphate backbone or the nitrogencontaining bases?
 The backbone is the same in all DNA
 The nitrogen bases contain the unique instructions.
 The DNA of all organisms on this planet contains
the same four bases. What might this indicate
about the origin of life on Earth?
 It suggests that the wide diversity of life that we see
might have stemmed from a common ancestor.
 What was one of the most powerful implications of the
Watson and Crick model of DNA?
 It (the model) suggested how DNA could be copied.
 The process by which DNA is copied during the cell
cycle.
 Replication.
 How does replication ensure that cells have complete
sets of DNA?
 It doubles the amount of DNA so that both of the
daughter cells resulting from mitosis have their own
complete set of DNA.
 Does DNA actually copy itself?
 No. Enzymes and proteins do the work of replication.
DNA merely stores information.
 Enzymes that form bonds between nucleotides during
replication.
 DNA polymerases.
 Describe the steps in the replication process.
 1.) Enzymes unzip the helix at numerous places. H
bonds are broken. Bases are exposed. Process proceeds
in 2 directions at the same time.
 2.) Free floating nucleotides pair with exposed bases.
DNA polymerases bond the nucleotides.
 3.) Two identical molecules of DNA result.
 Why is DNA replication called semiconservative?
 One old strand is conserved.
 One new strand is made.
 Roughly, how often do errors in replication occur?
 1 error per 1 billion nucleotides.
 Why does a cell need to replicate its DNA quickly?
 Our cells have a large amount of DNA. It must be
copied quickly enough to keep up with the demand
for cell division and to enable the cell to carry out
its normal functions.
 How do cells help insure that DNA replication is
accurate?
 Certain types of DNA polymerases have a built in
proofreading function that connects most
mispaired nucleotides.
 What is the central dogma, defined by Francis Crick
for molecular biology?
 Information flows in one direction…. From DNA to
RNA to proteins.
 What are the three processes of Francis Crick’s central
dogma?
 Replication, Transcription, Translation.
 The process that converts a DNA message into an
intermediate molecule, called RNA.
 Transcription.
 Interprets an RNA message into a string of amino
acids, called a polypeptide.
 Translation.
 In __________ cells, replication, transcription, and
translation all occur in the cytoplasm at approximately
the same time.
 Prokaryotic.
 In ______ cells, where DNA is located inside the
nuclear membrane, these processes are separated both
in location and time.
 Eukaryotic
 In ______ cells, replication and transcription occur in
the nucleus, while translation occurs in the cytoplasm.
 Eukaryotic.
 The __________ in eukaryotic cells goes through a
processing step before it can be transported out of the
nucleus.
 RNA
 RNA is a temporary copy of ____________ that is used
and then destroyed.
 DNA
 How do RNA and DNA differ?
 1) The sugar in RNA is ribose, which has one
oxygen atom more than DNA
 2) RNA has the base Uracil in place of thymine.
 3) RNA is a single strand of nucleotides.
 The single stand structure allows RNA to form
complex 3D shapes. Because of its structure, RNA
can catalyze reactions like an enzyme.
 The process of copying a sequence of DNA to produce
a complementary strand of RNA.
 Transcription.
 Just as replication is catalyzed by DNA polymerase,
transcription is catalyzed by ___________.
 RNA polymerase.
 Describe the first step in transcription for a
eukaryotic cell.
 RNA polymerase recognizes the start of a gene.
 RNA polymerase and other proteins assemble on
the DNA strand and unwinds the DNA molecule.
 Describe the second step in transcription.
 RNA polymerase, using only one strand of DNA as
a template, strings together a complementary
strand of RNA nucleotides.
 The growing RNA strand hangs freely as it is
transcribed, and the DNA helix zips back together.
 Describe the third step in the transcription process.
 Once transcribed, the RNA strand detaches from
the DNA segment.
 How RNA recognizes the end of the genes is
complicated. It varies with each type of RNA.
 What are the three major types of RNA produced by
transcription?
 mRNA messenger RNA
 rRNA ribosomal RNA
 tRNA transfer RNA
 An intermediate message that is translated to form a
protein.
 Messenger RNA (mRNA)
 Forms part of ribosomes, a cells protein factory.
 Ribosomal RNA (rRNA)
 Brings amino acids from the cytoplasm to a ribosome
to help make growing proteins.
 Transfer RNA (tRNA)
 Why must transcription occur in the nucleus of
eukaryotes?
 DNA is located in the nucleus of eukaryotes, so
processes involving DNA, such as transcription, must
occur there as well.
 Why does transcription produce more errors than
replication?
 Unlike DNA polymerase, RNA polymerase cannot
proofread the transcript being formed.
 Because most genes are transcribed many times, a few
defective copies of mRNA, and thus protein, usually
cause no harmful effects. These errors are not
transmitted to the next generation because the DNA is
not affected.
 Why must the DNA strand unwind and separate
before transcription can take place?
 The bases must be exposed so that free nucleotides
can pair with them.
 In the second step of transcription how does the base
sequence of the RNA transcript being formed compare
with the sequence on the template strand?
 It is complementary
 How is transcription similar to replication?
 1.) Both occur in the nucleus of eukaryotic cells.
 2.) Both are catalyzed by large, complex enzymes.
 3.) Both involve unwinding of the DNA double helix.
 4.) Both involve complementary base pairing to the
DNA strand.
 5.) Both processes are highly regulated by the cell.
 How do transcription and replication differ?
 Replication ensures that each new cell will have one
complete set of genetic instructions.
 Replication occurs only once during each round of
the cell cycle
 Transcription can make hundreds or thousands of
proteins.
 The process that converts, or translates, an mRNA
message into a polypeptide.
 Translation
 One or more polypeptides make up a ____________.
 Protein.
 Just as the ‘language’ of DNA uses C,G,T,A….. The
‘language’ of proteins uses _________ _________.
 Amino acids.
 The four nucleotides of DNA code for _________
amino acids.
 20
 A 3-nucleotide sequence that codes for an amino acid.
 Codon.
 The root of transcribe is “___ _______”
 The root of translate is “___ ________”
 To write
 To transfer
 Signals the end on an amino acid chain.
 Stop codon
 Signals the start of translation.
 Start codon
 The order in which a series of three nonoverlapping
nucleotide codons are read.
 Reading frame
 A set of three nucleotides that is complementary to an
RNA codon.
 Anticodon.
 Where does translation occur?
 In the cytoplasm of both prokaryotic and eukaryotic
cells.
 Explain the different roles of the large and small
ribosomal sub units.
 The small sub unit holds onto the mRNA transcript.
 The large subunit has three sites where the tRNA
molecules can dock; it helps form the peptide bond
between the amino acids and helps break the bond
between the amino acid and its carrier tRNA
molecules.
 Explain the connection between a codon and an
amino acid.
 A codon is a sequence of three nucleotides that
specifies a particular amino acid.
 Each tRNA molecule binds to a specific amino acid
and has an anticodon that binds to a specific
codon.
 Suppose a tRNA molecule had the anticodon AGU.
What amino acid would it carry?
 The tRNA molecule would recognize the mRNA codon
UGA, so it would carry the amino acid serine.
 The DNA of eukaryotic cells has many copies of
genes that code for rRNA molecules. Suggest a
hypothesis to explain why a cell needs so many
copies of these genes.
 rRNA is critical for making ribosomes to carry
out protein synthesis. rRNA must be made in
sufficient quantities to keep up with a cell’s
demand for various proteins.
 Prokaryotic cells turn genes on and off by controlling
___________.
 Transcription.
 The regulations of gene expression allows prokaryotic
cells, such as bacteria, to _____________.
 Better respond to stimuli.
 Conserve energy and materials.
 A DNA segment that allows a gene to be transcribed….
by helping RNA polymerase find where a gene starts.
 Promoter.
 A promoter interacts with proteins that increase the
rate of __________ or block __________ from
occurring.
 Transcription, transcription.
 Bacteria have much less DNA than do eukaryotes, and
their genes tend to be organized into ___________.
 Operons.
 An ___________ is a region of DNA that includes a
promoter, an operator, and one or more structural
genes that code for all the proteins needed to do a
specific task.
 Operon.
 Humans have an estimated 20,000 to 25,000 genes.
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Why wouldn’t you expect all these genes to be
transcribed and translated at the same time?
What might be an analogy to this in your own life?
The cell would run out of energy and raw materials
(amino acids and nucleotides).
Proteins would accumulate in the cell if they were not
needed.
Eating all of the food in the house at once
Everyone in the class talking at the same time (imagine
that)
 Why is the lac operon an advantage to a bacterial cell?
 The cell does not waste energy making enzymes to
digest lactose when lactose is not present.
 What happens when sonic hedgehog is missing in a
fruit fly?
 The embryos fail to form normal body segments.
 In eukaryotes ________ are nucleotide segments
that code for parts of the protein. ________ are
nucleotide segments that intervene, or occur,
between _________.
 Exons, introns, exons
 Which parts of a gene are expressed as protein: introns
or exons?
 Exons.
 In eukaryotic cells, genes each have a specific
combination of regulatory DNA sequences. How do
these combinations help cells carry out specialized
jobs?
 These combinations help a cell turn on only specific
genes. Based on the different genes that are turned on
or off, a cell has a unique set of proteins that enable it
to carry out certain functions
 Suppose a bacterium had a mutated repressor
protein that could not bind to the lac operator.
How might this affect regulation of the operator.
 The operon could never be turned off.
 The genes would be continually transcribed.
 A change in a organism’s DNA.
 Mutation.
 Generally, mutations that affect a single gene
happen during __________, whereas mutations
that affect a group of genes or an entire
chromosome happen during __________.
 Replication, meiosis.
 A mutation in which one nucleotide is substituted for
another.
 Point mutation.
 Mistakes during the replication process are usually
corrected by ____________.
 DNA polymerase
 The insertion or deletion of a nucleotide in the
DNA sequence. It usually affects a polypeptide
much more than does a substitution. It is a change
that throws off the reading frame, which results in
codons that code for different amino acids.
 Frameshift mutation
 A type of chromosomal mutation in which a
chromosome has two copies (or more) of a gene as
a result of crossing over.
 Gene duplication
 A type of chromosomal mutation in which a piece
of one chromosome moves to a nonhomologous
chromosome.
 Translocation
 In a mutation of a chromosome, what may be the
results of a substituted amino acid?
 It could affect protein folding or the function of the
protein itself. It could also cause a premature stop
codon.
 A mutation that does not affect the resulting
protein is called _____________.
 silent
 What is the difference between a mutation in a
germ cell and a mutation in a body cell?
 Mutations in body cells only affect that specific
organism. Mutations in germ cells are passed on to
offspring.
 Mutations may be a significant cause of
____________.
 aging
 Agents in the environment that can damage DNA.
 Mutagens
 Why do frameshift mutations have a greater effect
than point mutations?
 Point mutations typically affect only one codon. A
frameshift mutation affects all of the codons in a
gene that follow it.
 If GUA is changed to GUU, will the resulting
protein be affected? Explain.
 No, they both code for the amino acid valine.
 Explain how mutagens can cause genetic mutations
in spite of your body’s DNA repair enzymes.
 Mutagens may produce so much damage that the
repair enzymes cannot keep up with the repairs.
 Some genetic mutations are associated with
increased risk for a particular disease. Tests exist
for some of these genes. What might be the
advantages and disadvantages of being tested?
 Advantages: You would know to look for symptoms
and prepare for treatment.
 Disadvantages: There may be no cure. Having a
gene does not mean you will get the disease.
 How could a mutated gene produce a shorter
protein than that produced by the normal gene?
 A frameshift or a point mutation may have changed
one of the codons to a stop codon.
 What are some situations or circumstances in
which DNA testing could help identify someone or
something?
 Human remains are found that cannot be
identified by other means.
 People may need to determine parentage.
 DNA may be left at a crime scene.
 How might biotechnology help to repopulate the
Galapagos Islands with native tortoise species?
 Scientists could identify members of the
tortoise species that are native to the islands by
using DNA fingerprinting and then selectively
breeding those tortoises. DNA could also
identify family members so they are not used as
breeding pairs.
 Enzymes that cut DNA molecules at specific
nucleotide sequences.
 Restriction enzymes
 Also called endonuclease
 The sequence of nucleotides that is identified and
cut by a restriction enzyme.
 Restriction site
 Why are endonuclease also called restriction
enzymes?
 They restrict, or decrease, the effect of a virus on a
bacterial cell.
 What is the difference between a ‘sticky end’ of
DNA and a ‘blunt end’ of DNA?
 A blunt end is a straight cut across the two strands
of a DNA molecule. A sticky end is a staggered cut
that leaves tails of free DNA bases exposed.
 Fragments of DNA are separated and sorted
according to their sizes by a technique called _____
__________.
 Gel electrophoresis
 A map showing the lengths of DNA fragments
between restriction sites in a strand of DNA.
 Restriction maps
 What do the bands represent on a gel? (in gel
electrophoresis)
 The length of the DNA fragment
 List four different ways in which scientists can
manipulate DNA.
 DNA can be cut, copied, sequenced, and changed.
 What determines how DNA will be cut by a
restriction enzyme?
 The number and location of restriction sites
recognized by the restriction enzyme.
 How does gel electrophoresis separate DNA
fragments from each other?
 The DNA sample is loaded into a gel through
which an electrical current flows. The
negatively charged DNA fragments are pulled
toward the positive electrode. The largest
molecules move slowest, and the smallest move
quickest.
 Suppose you cut DNA. You know that you
should find four DNA fragments on a gel, but
only three appear, and one fragment is very
large. Explain what happened.
 This might indicate a mutation. One of the
restriction sites may have been deleted or
changed by the mutation, resulting in one very
large fragment where there should have been
two.
 What is the relationship between restriction sites
and a restriction map?
 A restriction map reveals the lengths of DNA
fragments between restriction sites. The more
restriction sites there are, the more fragments there
will be on the map.
 How do scientists get an amount of DNA that is
large enough to be studied and manipulated?
 They copy the same segment of DNA over and over
again using a technique called PCR (polymerase
chain reaction)
 What enzymes unwind and separate DNA
molecules?
 helicases
 A short segment of DNA that acts as the starting
point for a new strand.
 primer
 A representation of parts of an individual’s DNA
that can be used to identify a person at the
molecular level.
 DNA fingerprint
 A genetically identical copy of a gene or of an
organism.
 clone
 The altering of an organism’s DNA to give the
organism new traits.
 Genetic engineering
 DNA that contains genes from more than one
organism.
 Recombinant DNA
 Closed loops of DNA that are separate from the
bacterial chromosome and that replicate on their
own within the cell.
 plasmids
 An organism that has one or more genes from
another organism inserted into its genome.
 transgenic
 What is the greatest concern of genetically
engineering crops?
 All organisms in a transgenic population have the
same genome. A decrease in genetic diversity could
leave crops vulnerable to new diseases or pests.
 Why is the offspring of asexual reproduction a clone?
 The offspring of asexual reproduction are genetically
identical to the parent.
 What are plasmids, and how are they used in genetic
engineering?
 Plasmids are closed loops of bacterial DNA. New
genes can be incorporated into plasmids, and the
bacteria will produce the proteins coded for by genes.
 The study of genomes.
 Genomics
 By studying genomics, biologists who study evolution
can learn when closely related species __________
from each other.
 diverged
 All studies of genomics begin with _____ __________,
or determining the order of DNA nucleotides in genes
or in genomes.
 Gene sequencing
 The two main goals of the Human Genome Project
were to ……….
 1) map and sequence all of the genes within the
sequence.
 2) identify all of the genes within the sequence
 The HapMap project is working to ……….
 study how DNA sequences vary among people.
 The use of computer databases to organize and analyze
biological data.
 bioinformatics
 Tools that allow scientists to study many genes, and
their expression, at once.
 DNA microarray
 The study and comparison of all the proteins that
result from an organism’s genome.
 proteomics
 Describe the difference between gene sequencing and
DNA fingerprinting.
 Gene sequencing finds the DNA sequence; a DNA
fingerprint shows a number of repeated DNA
sequences.
 How is the study of specific genes different from the
study of a genome?
 Genomics studies all genes.
 How might genomics and proteomics help researchers
predict how a medical treatment might affect cells in
different tissues?
 By knowing about how genes and their products
interact, researchers could be able to predict how one
drug will affect many different areas of the body. They
could tailor a treatment to target a specific gene or
protein in order to avoid damaging others.
 The process of testing DNA to determine a person’s
risk of having or passing on a genetic disorder.
 Genetic Screening
 Why might genetic screening raise ethical concerns
about privacy?
 Genetic information may be used to discriminate
against a person in some way.
 The replacement of a defective or missing gene, or the
addition of a new gene, into a person’s genome to treat
a disease.
 Gene Therapy
 How is gene therapy similar to, and different from,
making a transgenic organism?
 They both involve inserting a new gene into an
organism, but gene therapy replaces a defective gene
with a normal gene in an adult organism; a transgenic
organism has genes from more than one species.