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143 terms

Microbiology Chapter 7

STUDY
PLAY
Genetics
Study of inheritance and inheritable traits as expressed in an organism's genetic material
Genome
The entire genetic complement of an organis. Includes its genes and nucleotide sequences
Prokaryotic chromosomes
Main portion of DNA, along with associated proteins and RNA
Haploid
Prokaryotic cells are _____(single chromosome copy)
Circular
Typical chromosome of prokaryote is _____molecule of DNA in nucleoid
Plasmids
Small molecules of DNA that replicate independently; Not essential for normal metabolism, growth, or reproduction
Fertility factors, Resistance factors, Bacteriocin factors, Virulence plasmids
types of plasmids
DNA Replication
Anabolic polymerization process that requires monomers and energy.
Triphosphate deoxyribonucleotides
_______ _______ serve both functions in structure and replicating genomes.
Complementary
Key to replication is ______ structure of the two strands
Replication
________ is semiconservative . New DNA composed of one original and one daughter strand.
Origin
Bacterial DNA replication begins at the _____.
5' to 3'
DNA polymerase replicates DNA only _____.
Antiparallel
Because strands are_____, new strands are synthesized differently
Leading strand
The strand synthesized continuously
Lagging strand
The strand synthesized discontinuously
bidirectional
DNA replication occurs________.
Topoisomerases
remove supercoils in DNA molecule
Methylated
DNA is ______.Control of genetic expression; Initiation of DNA replication; Protection against viral infection; Repair of DNA
Replication of eukaryotic DNA
Uses four DNA polymerases; Thousands of replication origins; Shorter Okazaki fragments; Plant and animal cells methylate only cytosine bases
Genotype
Set of genes in the genome
Phenotype
Physical features and functional traits of the organism
Transcription
Information in DNA is copied as RNA
Translation
Polypeptides synthesized from RNA
RNA; polypeptides
Central dogma of genetics; DNA transcribed to ____ and it is translated to form ______.
RNA primers, mRNA, rRNA, and tRNA
Four types of RNA transcribed from DNA
Nucleus, mitochondria, and chloroplasts
In eukaryotes, RNA transcription occurs in the _____, ______, and ______.
Polymerase and transcription
In eukaryotes there are three types of RNA ___________and numerous __________ factors.
Translation; capping, polyadenylation and splicing
mRNA is processed before ______ by:
Translation
Process where ribosomes use genetic information of nucleotide sequences to synthesize polypeptides
Messenger RNA; Transfer RNA; Ribosomes and ribosomal RNA
Participants in translation
Termination
Stage of translation when release factors recognize stop codons; Modify ribosome to activate ribozymes
Subunits
In termination, ribosome dissociates into _____.
Polypeptides
_______ released at termination may function alone or together
75%
____ of genes are expressed at all times;
Conserve energy
Other genes transcribed and translated when cells need them. This allows the cell to ____ ____.
Regulation of protein synthesis
Typically halts transcription; Can stop translation directly
Operon
An _____ consists of a promoter and a series of genes
Operator
Some operons are controlled by a regulatory element called an ______.
Inducible
_____operons must be activated by inducers
Lactose operon
Example of inducible operon
Repressible
______ operons are transcribed continually until deactivated by repressors
Tryptophan operon
An example of a repressible operon
Mutation
Change in the nucleotide base sequence of a genome; Rare event; Almost always deleterious
Mutations ______ leads to a protein that improves ability of organism to survive.
rarely
Point mutations
Most common mutation where one base pair is affected and it occurs in insertions, deletions, and substitutions.
Frameshift mutations
Nucleotide triplets after the mutation are displaced and results in insertions and deletions.
Radiation
Mutations can occur from ______, for example ionizing radiation and nonionizing radiation.
Chemical mutagens
Mutation that occurs nucleotide analogs; Disrupt DNA and RNA replication.
Nucleotide-altering chemicals
Result in base-pair substitutions and missense mutations
Frameshift mutagens
Result in nonsense mutations
Rare
Mutations are ____ events; Otherwise organisms could not effectively reproduce
Mutagens
________ increase the mutation rate by a factor of 10 to 1000 times
Mutants
Descendents of a cell that does not repair a mutation
Wild types
Cells normally found in nature
Positive selection, negative (indirect) selection and Ames test
Methods to recognize mutants
Homologous
Exchange of nucleotide sequences often mediated by _____sequences.
Recombinants
Cells with DNA molecules that contain new nucleotide sequences
Vertical gene transfer
Organisms replicate their genomes and provide copies to descendants
Horizontal gene transfer
Donor cell contributes part of genome to recipient cell
Transformation, transduction, and bacterial conjugation
Three types of horizontal gene transfer among prokaryotes
Transformation
One of conclusive pieces of proof that DNA is genetic material
Competent
Cells that take up DNA are _____. Results from alterations in cell wall and cytoplasmic membrane that allow DNA to enter cell
Generalized Transduction
Transducing phage carries random DNA segment from donor to recipient
Specialized transduction
Only certain donor DNA sequences are transferred
Transposons
Segments of DNA that move from one location to another in the same or different molecule
Transpositions
Result of transposons is a kind of frameshift insertion (_______)
Palindromic
Transposons all contain ________ sequences at each end
Genes
__ are composed of specific sequences of nucleotides that code for poylpeptides or RNA molecules
Genome
__ is the sum of all the genes and linking nucleotide sequences in a cell or virus.
Base pairs (bp)
the two strands of DNA are held together by hydrogen bonds between complementary __ ___ of nucleotides. Adenine bonds with thymine, and guanine bonds with cytosine
Chromosomes; nucleoid
bacterial and archaeal genomes consist of one ____, which are typically circular molecules of DNA associated with protein and RNA molecules, localized in a region of the cytosol called the ___
Histones
Archaeal DNA organizes around globular proteins called ___.
Plasmids
Prokaryotic cells may also contain one or more extra chromosomal DNA molecules called ___, which contain genes that regulate nonessential life functions, such as bacterial conjugation and resistance to antibiotics
Each newly synthesized strand of DNA remains associated with one of the parental strands
DNA replication is semiconservative
Leading strand; lagging strand
After helicase unwinds and unzips the original molecule, synthesis of each of the two daughter strands- called the ___ and the ___- occurs from 5' to 3'. Synthesis is mediated by enzymes that prime, join, and proofread the pairing of new nucleotides
Methylation
After DNA replication, ___ occurs.
Methylation
___ plays several roles, including the control of gene expression, the initiation of DNA replication, recognition of a cell's own DNA, and repair.
Genotype; phenotype
The ___ of an organism is the actual set of genes in its genome, whereas its ___ refers to the physical and functional traits expressed by those genes
RNA primer; messenger RNA; tRNA; rRNA
RNA has several forms. These include ___; ____, which carries genetic information from DNA to a ribosome; ___, which carries amino acids to the ribosome, and ___, which, together with polypeptides, makes up the structure of ribosomes
Central dogma
The ___ of genetics states that genetic information is transferred from DNA to RNA to polypeptides, which function alone or in conjunction as proteins
Transcription; RNA polymerase
The transfer of genetic information begins with ___ of the genetic code from DNA to RNA, in which ___ links RNA nucleotides that are complementary to genetic sequences in DNA.
Promoter; terminator
Transcription begins at a region of DNA called a ___ and ends with a sequence called a ___. In bacteria, Rho protein may assist in termination, or termination may depend solely on the nucleotide sequence of the transcribed RNA
Introns; exons
eukaryotic mRNA is synthesized as pre-messenger RNA. Before translation can occur, a spliceosome removes noncoding ___ from pre-mRNA and splices together the ___, which are the coding sections
Translation
In ___, the sequence of genetic information carried by mRNA is used by ribosomes to construct polypeptides with specific amino acid sequences
Codons; anticodons
The genetic code consists of triplets of mRNA nucleotides, called ___. These bind with complementary ___ on transfer RNAs.
tRNA
___ are molecules that carry specific amino acids
Ribosomal RNA
___ catalyzes the bonding of one amino acid to another to form a polypeptide.
Amino acids
A sequence of nucleotides thus codes for a sequence of ___ ___.
Operon; operator
an __ is a series of prokaryotic genes, a promoter, and in some cases an ___ sequence, all controlled by one regulatory gene.
Inducible operons
___ are normally "turned off" and are activated by inducers that block repressors from binding to the operator.
Repressible operons
___ are normally "on" and are deactivated by repressors that bind to the operator
Mutation
a ___ is a change in the nucleotide base sequence of a genome.
Point mutations; substitutions; frameshift mutations
___ involve a change in a nucleotide base pair and include ___ and two types of ____
Insertions and deletions
two types of frameshift mutations
Silent, missense, nonsense mutations
Mutations can be categorized by their effects as ___, ___, or ___
Mutagens
physical or chemical agents called ___ can increase the normal rate of mutation.
Mutants; wild-type; positive selection, negative (indirect) selection, Ames test; carcinogens
Researchers have developed methods to distinguish ___, which carry mutations, from normal ___ cells. These methods include ___, ___, and the ___, which is used to identify mutagens, which may be potential ____
Genetic recombination
organisms acquire new genes through ___, which is the exchange of segments of DNA. Crossing over occurs during gamete formation, part of sexual reproduction in eukaryotes
Horizontal (lateral) gene transfer; donor cell; recipient cell
Vertical gene transfer is the transmission of genes from parents to offspring. In ___, DNA from a ___ is transmitted to a ____.
Recombinant cell
A ___ results from genetic recombination between donated and recipient DNA.
Transformation, transduction and bacterial conjugation
___, ___, and __ are types of horizontal gene transfer
Transformation; competent
In ___ a ___ recipient prokaryote takes up DNA from its environment. Competency is found naturally or can be created artificially in some cells
Transduction; bacteriophage; phage
In ___, a virus such as __, or ___, carries DNA from a donor cell to a recipient cell
Transducing phages
Donor DNA is accidentally incorporated in such ___ ___
Conjugation ; F (fertility) plasmid (factor); conjugation pilus
In ___, an F+ bacterium -that is, one containing an _____- forms a ____ that attaches to an F- recipient bacterium . Plasmid genes are transferred to the recipient, which becomes F+ as a result
Transposons; inverted repeats (IR); transposition; insertion sequences (IS); Complex transposons
___ are DNA segments that code for the enzyme transposase and have palindromic sequences known as ___ at each end. Transposons move among locations in chromosomes in eukaryotes and prokaryotes- a process called ___. The simplest transposons, known as ___, consist only of inverted repeats and transposase. ___ contain other genes as well.
a. 4,000,000
which of the following is most likely the number of base pairs in a bacterial chromosome?
a. 4,000,000
b. 4000
c. 400
d. 40
c. they are located in the cytosol
which of the following is a true statement concerning prokaryotic chromosomes?
a. they typically have two or three origins of replication
b. they contain single-stranded DNA
c. they are located in the cytosol
d. they are associated in linear pairs
d. extra chromosomal DNA
a plasmid is __
c. histone
which of the following forms ionic bonds with eukaryotic DNA and stabilizes it?
a. chromatin
b. bacteriocin
c. histone
d. nucleosome
carry energy.
are found in four forms, each with a deoxyribose sugar, a phosphate, and a base
are present in the cytosol of cells as triphosphate nucleotides
Nucleotides used in the replication of DNA ___
a. DNA polymerase III
which of the following molecules function as a "proofreader" for a newly replicated strand of DNA?
a. DNA polymerase III
b. primase
c. helicase
d. ligase
a. methylation
the addition of -CH3 to a cytosine nucleotide after DNA replication is called ___
d. E site
in translation, the binding site through which tRNA molecules leave is called the ___
uses auxotrophs and liver extract to reveal potential mutagens
The Ames test ____
c. transcription
which of the following is NOT a mechanism of natural genetic transfer and recombination?
a. transduction
b. transformation
c. transcription
d. conjugation
d. competent
Cells that have the ability to take up DNA from their environment are said to be ___
a. conjugation requires a sex pilus extending from the surface of a cell
Which of the following statements is true?
a. conjugation requires a sex pilus extending from the surface of a cell
b. conjugation involves a Cfactor
c. conjugation is an artificial genetic engineering technique.
d.conjugation involves DNA that has been released into the environment from dead organisms
d. transponsons
which of the following are called "jumping genes"?
a. Hfr cells
b. transducing phages
c. palindromic sequences
d. transponsons
c horizontal gene transfer
although cells P and Q are totally unrelated, cell Q receives DNA from cell P and incorporates this new DNA into it chromosome. This process is ___
b. codon
which of the following is part of each molecule of mRNA?
a. palindrome
b. codon
c. anticodon
d. base pair
a five-carbon sugar
phosphate
a nitrogenous base
a nucleotide is composed of ___
two/thymine
in DNA, adenine forms __ hydrogen bonds with ___
an Okazaki fragment
a sequence of nucleotides formed during replication of the lagging DNA strand is __
c. origin
which of the following is NOT part of an operon?
a. operator
b. promoter
c. origin
d. gene
RNA transcription
repressible operons are important in regulating prokaryotic ___
RNA molecules
transcription produces ___
lagging strand replication
ligase plays a major role in ___
lasting
beneficial
inheritable
before mutations can affect a population permanently, they must be ___
active/ a repressor
the trp operon is repressible. This means it is usually ___ and is directly controlled by ___
initiation of transcription, elongation of the RNA transcript, termination of transcrition
The three steps in RNA transcription are __, __, and ___.
codon
a triplet of mRNA nucleotides that specifies a particular amino acid is called a ___
silence, missense, nonsense
Three effects of point mutations are ___, ___, and ___
frameshift
insertions and deletions in the genetic code are also called ___ mutations
promoter, operator, a series of genes
an operon consists of ___, ____, and ___ and is associated with a regulatory gene
inducible
in general, ___ operons are inactive until the substrate of their genes' polypeptides is present
semiconservative
a daughter DNA molecule is composed of one original strand and one new strand because DNA replication is ____
transformation, transduction, bacterial conjugation
A gene for antibiotic resistance can move horizontally among bacterial cells by ___, ___, and ____
transposons
___ are nucleotide sequences containing palindromes and genes for proteins that cut DNA strands.
crossing over
____ ____ is a recombination event that occurs during gamete formation in eukaryotes
transfer
___ RNA carries amino acids
short interference, micro
___ RNA and ___ RNA are antisense; that is, they are complementary to another nucleic acid molecule