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Chpt 8 Genetics
Terms in this set (71)
A gene is defined as
a sequence of nucleotides in DNA that codes for a functional product.
Protein synthesis in eukaryotes is similar to the process in prokaryotes in that both eukaryotes and prokaryotes
use codons to determine polypeptide sequences.
Bacteria usually contain multiple chromosomes.
Which of the following build(s) new strands of DNA?
Which statement about DNA replication is CORRECT?
The leading strand is built continuously, and the lagging strand is built in pieces.
During DNA replication, which nucleotide will bind to an A nucleotide in the parental DNA?
The molecule that seals the gaps between the pieces of DNA in the lagging strand is
Which statement about DNA replication is FALSE?
DNA ligase adds nucleotides to the lagging strand.
Which of the following events occurs during transcription?
A molecule of RNA is formed based on the sequence of nucleotides in DNA.
Which of the following is a correct statement about mRNA?
mRNA moves from the nucleus to the cytoplasm following RNA processing.
The site of translation is
ribosomes in the cell cytoplasm.
Which one of the following does not play a role in translation?
Which of the following does not occur during RNA processing?
mRNA attaches to the small subunit of a ribosome.
Which of the following genetic elements is transcribed into a single mRNA?
The structural genes
Which operons are always transcribed unless deactivated?
Which operons are never transcribed unless activated?
According to the animation, where on the DNA strand does a repressor bind?
What is the inducer molecule in the lac operon?
With which genetic region does the repressor protein interact?
The operator region
When the cell is not in the presence of lactose,
the repressor proteins bind to the operator
What is the basic function of the lac operon?
To code for enzymes involved in catabolizing lactose.
According to the animation, to what genetic element does the RNA polymerase bind?
When the cell is NOT in the presence of tryptophan,
RNA polymerase can transcribe mRNA
When is the repressor protein transcribed?
It is always transcribed.
Why is the tryptophan operon turned off in the presence of tryptophan?
Tryptophan binds to and activates the repressor proteins; the repressor proteins, in turn, bind to the operator, preventing transcription.
What is the overall function of the trp operon?
To ensure that the cell has a supply of tryptophan at all times
According to the animation, how do the repressor proteins block the transcription of the structural genes?
It binds to the operator when activated.
Thymine dimers result from
Which of the following might result in a frameshift mutation?
Which of the following describes how 5-bromouracil might create a mutation?
It can replace the base thymine, and can base pair with guanine rather than adenine.
increase the likelihood of mutations in DNA.
A nucleotide-altering chemical
can alter nitrogenous bases of DNA, resulting in incorrect base pairing.
What is considered to be the average natural mutation rate that occurs during DNA replication?
One in every billion nucleotides replicated.
A mutation that affects the genotype of the organism but not the phenotype is called a
A base insertion or deletion in the translated region of the gene may lead to
A base substitution that changes a codon coding for an amino acid to a stop codon is called a
How frequently do silent mutations occur?
One out of every three mutations
Competent cells are cells that
can take up DNA from their surrounding environment and integrate it into their own chromosomes by recombination.
Mice that are injected with only the R strain of Streptococcus pneumoniae
stay healthy, because their immune systems can kill this strain easily.
What characteristic of the S strain allows it to evade the immune system of the mice?
The cells have a capsule.
What most likely explains the recovery of live S strain cells from a mouse injected with heat-killed S strain mixed with live R strain cells?
The R strain picked up the S strain DNA, enabling it to produce a capsule.
Which finding is most surprising from Griffith's experiments?
S strain cells are isolated from the blood of mice infected with heat-killed S strains and live R strains.
What is unique about transduction compared to normal bacteriophage infection?
Transduction transfers DNA from the chromosome of one cell to another.
How is generalized transduction different from specialized transduction?
Generalized transduction is initiated during lytic cycle of a virulent bacteriophage; specialized transduction is initiated during the lysogenic cycle of a temperate bacteriophage.
A transducing phage
contains fragments of the host chromosome instead of the viral genome.
When a transducing phage interacts with a new host cell,
the DNA from the previous host can recombine with the new host chromosome.
Bacterial conjugation is often referred to as bacterial sex. Why is this term inaccurate?
Conjugation does not result in the formation of new offspring.
What must occur for bacterial conjugation to take place?
The cells must come into contact with each other.
Which statement about conjugation is false?
Conjugation is a process of bacterial reproduction
Based on the animation, what is transferred during bacterial conjugation?
A bacterial plasmid
What is the function of the conjugation pilus?
It pulls the F+ and F- cells together.
What is required by an F- cell to become an F+ cell?
What is the key difference between donor cells and recipient cells?
A F plasmid
What cellular macromolecule is the fertility factor comprised of?
At which point does a recipient cell become an F+ cell?
1.Fusion of the cell membranes
2.Attachment of the sex pilus
3.Transfer of the single stranded F factor
4.Pulling of donor and recipient cells together
5.Formation of the complementary strand of the F factor
How does an F+ cell differ from an Hfr cell?
Hfr strains have the F plasmid integrated into the chromosome.
Why does conjugation between an Hfr strain and an F- strain not result in two Hfr strains?
Conjugation is typically disrupted before the fertility factor can be transferred.
Which of the following is a characteristic of an F+ cell?
Ability to synthesize sex pili, presence of a fertility factor, and ability to mate with an F- cell.
What benefit does the F- strain receive from mating with an Hfr strain?
It acquires new, potentially beneficial genes from the Hfr strain.
Which type of transposon would contain a gene for transposase?
Both simple and complex transposons
How do complex transposons differ from simple transposons?
Complex transposons code for additional genetic elements, such as antibiotic resistance genes; simple transposons only code for the transposase gene essential for the tranposon itself.
Insertion sequences target which areas on a target DNA sequence?
A sequence of nucleotides identical to the inverted repeat sequence found on the insertion sequence itself
What makes an insertion sequence different from other DNA sequences found in a cell?
They are capable of effecting their own movement from one location to another on DNA.
If the gene that codes for transposase is mutated so that it no longer produces the fully functional enzyme, how will the insertion sequence be affected?
The insertion sequence would lose its ability to effect its own movement.
How does replicative transposition differ from cut-and-paste transposition?
Replicative transposition results in the transposon being copied to a new location; in cut-and-paste transposition, the entire transposon moves to the new location.
How is a complex transposon different from a simple transposon?
They have two simple transposons with another DNA sequence between them.
Why does a complex transposon often contain an extra piece of DNA between the two insertion elements?
It is often a gene that confers a survival advantage to the host, such as antibiotic resistance.
How would you be able to determine if the Tn5 transposon you put into a bacterium integrated into the host genome?
If the Tn5 transposon integrated into the host genome, the cells would show resistance to the antibiotic kanamycin.
How does specialized transduction differ from regular lysogeny?
The prophage in specialized transduction carries with it pieces of the host chromosomal DNA.
What happens to the packaged DNA of a specialized transduced phage when it infects a new recipient cell?
The host DNA integrates, with the prophage, into the new recipient chromosome.
How can specialized transduction contribute to the transfer of antibiotic resistance genes in a bacterial population?
The prophage takes an antibiotic resistance gene with it and is packaged with the newly synthesized viral DNA.
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