microbiology chapter 9
The three basic categories of genes:
1. genes that code for proteins 2. genes that code for RNA 3. genes that control gene expression
The inducible operon is made of 3 segments:
1. regulator 2. control locus 3. structural locus
The science of genetics explores:
1. transmission of biological traits from parent to offspring 2. expression and variation of those traits 3. structure and function of genetic material 4. how this material changes
A DNA triplet encodes ________________ mRNA codon and ________________ amino acid
1; 1
Adenine binds to thymine with ___________ hydrogen bonds
2
In a chromosome, the DNA is composed of ________________ strand(s)
2
________________ replication forks are formed form opening a section of the parental DNA molecule during replication
2
Guanine binds to cytosine with ___________ hydrogen bonds
3
Nucleotides can only be added to the _______________ end of a growing chain
3'
The mRNA chain is built in the ________________ direction
5' to 3'
________________ are transcribed from a DNA template
All types of RNA
The ________________ test is used to determine the carcinogenic potential of a chemical
Ames
Agricultural, industrial, and medicinal compounds are screened using the
Ames test
__________ are found on mRNA, and __________ are found on tRNA
Codons; anticodons
Which of the following is NOT a result of transposon activity in bacteria? Changes in traits such as colony morphology, pigmentation, and antigenic characteristics Replacement of damaged DNA Transfer of drug resistance in bacteria Correction of ultraviolet radiation mutations
Correction of ultraviolet radiation mutations
Genes are made up of ________________, a macromolecule made up of nucleotides
DNA
Genome of cells is
DNA
Genome of viruses is
DNA or RNA
What enzyme is responsible for building strands of DNA?
DNA polymerase
What proofreads nucleotides during DNA replication?
DNA polymerase
___________ removes the RNA primers and replaces them with DNA
DNA polymerase I
The enzymes responsible for building the DNA strand, proofreading newly produced DNA strands, and removing the RNA primer are
DNA polymerase I and II
___________ adds nucleotides in a 5' to 3' direction
DNA polymerase III
What determines the order of amino acids in the primary structure of a protein?
DNA sequence of a gene
In bacterial conjugation a ________________ refers to a donor cell with a fertility plasmid located in the cytoplasm
F+
In bacterial conjugation, ________________ refers to a recipient cell that does not have a fertility plasmid
F-
Addition or deletion of bases that changes the reading of mRNA codons
Frameshift mutation
What are the two types of transduction?
Generalized and specialized transduction
Random fragments of disintegrating host DNA are picked up by the phage during assembly; any gene can be transmitted this way. What type of transduction?
Generalized transduction
DNA polymerase ________________ is the enzyme responsible for building the DNA strand
III
The enzyme involved in replicating a new DNA strand is DNA polymerase ________________, and the DNA polymerase ________________ is involved in removing the RNA primer, closing gaps, and repairing mismatched bases.
III; I
What is the order of transcription?
Initiation, Elongation, Termination
Transcribed version of a structural gene or genes in DNA
Messenger RNA
DNA replication begins at an
ORI (origin of replication)
What can be shared between bacteria through conjugation to help them survive the effects of antibiotics?
R-factors or resistance factors
The large enzyme complex involved in synthesizing RNA from a DNA template is
RNA polymerase
The main enzyme responsible for transcription is
RNA polymerase
Please order the following to represent the stages from beginning to end of the transcription process: RNA polymerase dissociates from the DNA strand at a specific sequence. RNA polymerase builds the mRNA strand based on the DNA sequence. RNA polymerase binds to the promoter region on the DNA strand.
RNA polymerase binds to the promoter region on the DNA strand. RNA polymerase dissociates from the DNA strand at a specific sequence. RNA polymerase builds the mRNA strand based on the DNA sequence.
In the first step of transcription, ___________ binds to a ___________ region upstream of the gene
RNA polymerase; promoter
During transcription, RNA polymerase synthesizes ________________ from a ________________ template
RNA; DNA
___________ technique allows identification of mutants
Replica Plating
Random change in the DNA arising from errors in replication that occur without a known cause
Spontaneous mutation
Changing of single base in the DNA code that may result in the placement of a different amino acid
Substitution mutation
Can move from one chromosome site to another, from a chromosome to a plasmid, or from a plasmid to a chromosome
Transposons
Special DNA segments that have the capability of moving from one location in the genome to another - "jumping genes"
Transposons
What is the specific sequence of 3 mRNA nucleotides that encodes a particular amino acid?
a codon
The main effect of ultraviolet radiation on DNA is
abnormal bonding between adjacent pyrimidines
The ________________ of tRNA is complementary to the mRNA codon in translation
anticodon
When a mutated gene reverses to its original base composition
back-mutation
In eukaryotic cells, what cellular structure is composed of a neatly packaged DNA molecule?
chromosome
What is a discrete cellular structure composed of a neatly packaged DNA molecule?
chromosome
Donor and recipient bacterial cells are connected by the sex pilus during
conjugation
During ________________, bacterial cells are in direct contact
conjugation
What is the transfer of a plasmid or chromosomal fragment from a donor cell to a recipient cell via a direct connection?
conjugation
Composed of promoter and operator
control locus
When excess arginine is present, it binds to the repressor and changes it. Then the repressor binds to the operator and blocks arginine synthesis. Arginine is the
corepressor
A nucleotide is oriented 5' to 3' depending on the location of the ________________ on the strand of DNA
deoxyribose carbons
What are the 3 parts of a nucleotide in DNA?
deoxyribose sugar, phosphate, and nitrogenous base
RNA viruses compared to DNA viruses:
enter host cell in RNA form virus cycle occurs in cytoplasm smaller genomes
Proteins contribute to the phenotype of an organism by functioning as:
enzymes and structural molecules
Proteins that remove incorrect bases and replace them with correct ones are termed ________________ repair enzymes
excision
Gram-negative cell donor has a _______ that allows the synthesis of a conjugative pilus
fertility plasmid
Recipient cell is a related species or genus without a
fertility plasmid
________________ mutations are generally most harmful to cells because they cause the greatest change in the amino acid sequence of a protein
frameshift
The segment of DNA that contains the necessary code to make a protein or RNA molecule
gene
The site on the chromosome that provides information for a certain cell function
gene
Chromosome is subdivided into ___________, the fundamental unit of heredity responsible for a given trait
genes
What is the study of heredity?
genetics
What is the study of the inheritance of living things?
genetics
The ______ is the sum total of genetic material in a cell.
genome
What is the sum total of genetic material of a cell? (chromosomes + mitochondria/chloroplasts and/or plasmids)
genome
All types of genes constitute the genetic makeup
genotype
An organism's genetic makeup is referred to as its ________________, whereas the expression of those genes is referred to as the organism's ________________
genotype; phenotype
What are the purine nitrogenous bases found in DNA?
guanine and adenine
What unwinds and unzips the DNA double helix?
helicase
What is another term for genetics - the study of inheritance in living things?
heredity
When one bacterium donates DNA to another bacterium, a type of genetic recombination known as _________ has occurred.
horizontal gene transfer
________________ mutations occur as a consequence of exposure to chemical or physical mutagens
induced
Results from exposure to known mutagens, physical (primarily radiation) or chemical agents that interact with DNA in a disruptive manner
induced mutations
Lactose turns on the operon on by acting as the
inducer
The lactose operon is an ___________ operon
inducible
When a operon is turned ON by a substrate; catabolic operons - enzymes needed to metabolize a nutrient are produced when needed
inducible
The three events of translation in the correct order are ________________, ________________, ________________, followed by protein folding and processing
initiation, elongation, termination
Translation occurs in five stages:
initiation, elongation, termination, protein folding, and processing
What are intervening sequences of noncoding DNA?
introns
The __________ operon is normally in an off mode and does not initiate enzyme synthesis when the appropriate substrate is absent.
lac
Binding of ___________ to the repressor protein changes its shape and causes it to fall off the operator. RNA polymerase can bind to the promoter. Structural genes are transcribed
lactose
The ___________ operon is normally off
lactose
A ________________ mutation results in a different amino acid being incorporated into a protein, with varying results
missense
Eukaryotic chromosomes are
multiple and linear
A ________________ defines a chemical or physical agent that induces a change in DNA
mutagen
A chemical or physical agent that induces a change in DNA is referred to as a
mutagen
________________ refers to an organism that has a mutation
mutant
An organism that has a mutation is a ___________, showing variance in morphology, nutritional characteristics, genetic control mechanisms, resistance to chemicals, etc
mutant strain
A ________________ is a permanent inheritable alteration in the DNA sequence of a cell
mutation
A change in phenotype due to a change in genotype is called a
mutation
A small number of ________________ are considered beneficial in that they provide one cell with a useful change in structure or physiology
mutation
Genetic ______ and the variations they produce result in population changes and thus, evolution.
mutations
Mutations leading to _________ are harmful, possibly fatal
nonfunctional proteins
A ________________ mutation changes an amino acid producing codon into a stop codon, leafing to premature termination of a protein
nonsense
A ________________ mutation results in early termination of the protein
nonsense
Changes a normal codon into a stop codon
nonsense mutation
The result of a point mutation that changes a template gene sequence from 3'-TACGCCATATAT-5' to 5'-TACGCCATCTAT-5' is an example of a
nonsense mutation
The ________________ DNA strand is the strand that is not directly used for transcription into mRNA during protein synthesis
nontemplate
Basic unit of DNA structure is a
nucleotide
What is the basic unit of DNA structure?
nucleotide
Where does transcription occur in eukaryotic cells?
nucleus
A(n) _______ is a section of prokaryotic DNA that contains one or more genes along with a corresponding operator to control transcription.
operon
In prokaryotes the regulation of genes is coordinated by ___________, a set of genes, all of which are regulated as a single unit
operons
Prokaryotic DNA is arranged into systems called
operons
A ________________ serves as the vector for transduction in bacteria
phage
The expression of the genotype creases traits referred to as the
phenotype
The expression of the genotype creates observable traits
phenotype
________________ repairs DNA that has been damaged by ultraviolet radiation using visible light
photoactivation
DNA ______________ is a light-sensitive enzyme able to repair DNA damaged by ultraviolet radiation.
photolyase
In bacterial conjugation, a donor cell with a F (fertility) ________________ located in the cytoplasm is considered F+
plasmid
What are found in fungi and bacteria, but not plants or viruses?
plasmids
What are small circular segments of DNA found in the cytoplasm of prokaryotes that is capable of independent replication and usually contains nonessential genes?
plasmids
The genome of a prokaryotic or eukaryotic cell includes DNA found in:
plasmids, chromosomes, mitochondria, and chloroplasts
Mutations that involve the addition, deletion, or substitution of a single base are referred to as ________________ mutation
point
The addition, deletion, or substitution of a few bases
point mutation
What allows for the synthesis of many protein molecules simultaneously from the same mRNA molecule?
polyribosomal complex
Any change that confers an advantage during selection pressure will be retained by the
population
Gram-________________ cells conjugate and transfer genetic material through pores in their cell walls instead of pili
positive
An RNA primer is synthesized at the origin of replication by
primase
Splicing does not occur in
prokaryotes
What are functional biomolecules in cells formed from one or more long chains of amino acids?
proteins
During posttranslational modification:
proteins join with other proteins to form quaternary structures cofactors are added to proteins destined to become enzymes
In DNA, a purine always combines with a
pyrimidine
What compose ribosomal subunits?
rRNA
What is a component of ribosomes where protein synthesis occurs?
rRNA
________________ refers to the transfer of genes from donor to recipient microorganisms
recombination
During semiconservative ________________ the DNA is duplicated prior to binary fission
replication
________________ of positive-strand ssRNA requires the synthesis of a negative strand which becomes a master template to create new daughter strands
replication
Arginine operon is a ___________ operon
repressible
Retroviruses contain the enzyme
reverse transcriptase
The 5 carbon sugar in RNA is
ribose
What is the pentose sugar found in RNA?
ribose
All the elements needed to synthesize protein are brought together on the
ribosomes
DNA replication is said to be
semi-conservative
Alters a base but does not change the amino acid
silent mutation
Bacterial chromosomes are a
single circular loop
RNA virus genomes are usually ________________ than DNA virus genomes
smaller
________________ mutations are due to random mistakes in replication
spontaneous
A random change in the DNA due to errors in replication that occur without known cause
spontaneous mutations
________________ genes encode a specific functional protein.
structural
What are genes that code for proteins?
structural genes
What are the components of an operon in a sequence of DNA?
structural genes, operator, promoter
Made of 3 genes each coding for an enzyme needed to catabolize lactose
structural locus
What is made from DNA; secondary structure creates loops; bottom loop exposes a triplet of nucleotides called an anticodon which designates a specificity and complements mRNA; carries specific amino acids to ribosomes?
tRNA
When RNA polymerase reaches the ________________ site on the DNA template, the newly formed mRNA sequence is relesased
termination
What is the primary structure of a protein?
the chain of amino acids bound by peptide bonds
Both herpesvirus and Hepatitis B virus insert their DNA into the host genome increasing
the risk of cancer
Bacteriophage serves as a carrier of DNA from a donor cell to a recipient cell
transduction
What are the three types of RNA?
transfer RNA messenger RNA ribosomal RNA
The RNA type that transfers amino acids to the growing peptide chain in translation is
transfer RNA (tRNA)
Chromosome fragments from a lysed cell are accepted by a recipient cell; the genetic code of the DNA fragment is acquired by the recipient
transformation
During the process of ________________ a competent bacterial cell may accept soluble DNA from the surrounding environment.
transformation
Griffith's experiment using Streptococcus pneumoniae demonstrated the process of
transformation
The acceptance by a bacterial cell of small DNA fragments from the surrounding environment is termed ________.
transformation
What is a useful tool in recombinant DNA technology
transformation
________________ is the gene transfer method that involves the uptake of free DNA by competent bacterial cells
transformation
The ssRNA of positive-strand viruses come ready to be ________________ into proteins
translated
During ________________, mRNA is converted into a protein
translation
The two steps of protein synthesis are
translation and transcription
During translation elongation:
translocation of ribosome tRNA delivers amino acid to empty A site peptide bond forms between adjacent amino acids
________________ are able to shift from one part of the genome to another
transposons
Result from exposure to known mutagens, which are primarily physical or chemical agents that damage
DNA Induced mutation
What specifies how to make proteins?
DNA blueprint
What is the central dogma hypothesis of genetics?
DNA encodes RNA which encodes protein
Forms a complex cellular structure that contributes to the process of translation
Ribosomal RNA
A highly specific part of the host genome is regularly incorporated into the virus
Specialized transduction
Contains the anticodon and an amino acid binding site
Transfer RNA
Transduction occurs through a
bacteriophage
Any nitrogen containing molecule found in DNA and RNA that provides the basis for the genetic code is a nitrogenous ________________
base
Organisms with mutations that are _________ in their environment can readily adapt, survive, and reproduce - these mutations are the basis of change in populations
beneficial
Initiation of transcription involves:
binding of RNA polymerase to promoter region
DNA polymerases are responsible for:
building the DNA chain and proofreading/repair
DNA complexed with protein constitutes the genetic material as
chromosomes
Each mRNA ________________ codes for a particular amino acid which is the bonded with other amino acids during translation to form a protein
codon
When _______ occurs, a portion of the chromosome and a portion of the fertility plasmid are transferred to the recipient
conjugation
________________ in bacteria refers to horizontal gene exchange via pili
conjugation
What are the 3 means for genetic recombination?
conjugation trasformation trasduction
Where does translation occur in eukaryotic cells?
cytoplasm
What are the pyrimidine nitrogenous bases found in DNA?
cytosin and thymine
The purine guanine pairs with the pyrimidine ________________
cytosine
In a repressible operon, excess product acts as a corepressor to __________ the transcription of the operon.
decrease
What is the pentose sugar found in DNA?
deoxyribose
What locates and repairs incorrect sequence by removing a segment of the DNA and then adding the correct nucleotides?
excision repair
A ________________ mutation results from an insertion or deletion of nucleotides, leading to a shift of the triplet sequence from the point of mutation downstream
frameshift
When the reading frame of the mRNA is altered
frameshift mutation
___________ are regulated to be active only when their products are required
genes
What must be replicated before a cell can divide through binary fission?
genetic material
What occurs when an organism acquires and expresses genes that originated in another organisms?
genetic recombination
In the absence of ___________, the repressor binds with the operon locus and blocks transcription of downstream structural genes
lactose
Synthesized 5' to 3' in short segments; overall direction is 3' to 5'
lagging strand
Synthesized continuously in 5' to 3' direction
leading strand
When replication forks meet, ___________ link the DNA fragments along the lagging strang
ligases
What is used for UV light damage?
light repair
What carries DNA message through complementary copy; message is in triplets call codons
mRNA
________________ contains the codons for the polypeptide
mRNA
What is the RNA form that contains the transcribed code for a protein from the original DNA strand?
messenger RNA (mRNA)
What locates and repairs mismatched nitrogen bases that were not repaired by DNA polymerase?
mismatch repair
Causes change in a single amino acid
missense mutation
Several DNA viruses are known to be inhibitors of cancer and are thus termed
oncongenic
What type of bacterial cells conjugate?
only gram-negative
Gene that codes for repressor
regulator
What are genes that control gene expression?
regulatory genes
What is splicing?
removal of introns and connection of exons
Normally on and will be turned off when the product of the pathway is no longer required
repressible
When genes in a series are turned OFF by the product synthesized; anabolic operon - enzymes used to synthesis an amino acid stop being produced when they are not needed
repressible
Part of the lactose operon:
structural locus, control locus, regulator
Nucleotides covalently bond to form a
sugar-phosphate backbone
What are 2 functions of RNA polymerase?
synthesizes an RNA molecule from DNA template unwinds the DNA so that transcription can take place
Donor and recipient cells can be unrelated in
tranformation
One reason protein synthesis is more efficient in bacteria that in eukaryotes because bacterial ________________ and ________________ are simultaneous.
transcription; translation
________________ involves transfer of DNA via bacteriophages
transduction
A ________________, synonymous with codon, describes a trinucleotide sequence coding an amino acid in mRNA
triplet
Griffith's experiment using Streptococcus pneumoniae demonstrated that:
two different strains of S. pneumoniae transformed into a third unique strain
The native or ________________ type strain describes cells that carry nonmutated DNA
wild
A natural, nonmutated characteristic is known as a
wild type