Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BIMM 120 > Chapter 10 > Flashcards

Chapter 10 Flashcards

1
Q

What is molecular genetics

A

It is the genetic research with bacteria and phage that led to the discovery of genes, DNA, the molecular basis of inheritance, transcription, translation, the genetic code and biochemical pathways

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How were these studies carried out

A

It started with the isolation of bacterial or phage mutants that are defective for a certain process that is being studied. This leads to the identification of the genes that are required for carrying out that process, which leads to the proteins that the genes encode for and the molecular basis of the phenotype

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is a mutation

A

A heritable change in genome sequence that can potentially lead to a change in phenotype

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is a phenotype

A

Observable properties of an organism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is a mutant

A

Any organism, cell, or virus differing from the parental strain in genotype

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is a genotype

A

The nucleotide seqeunce of genome. A mutant contains mutation(s) in its genome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is WT (wild type)

A

Typically refers to strains isolated from nature, but depends on context, and often refers to a standard research strain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are selectable mutations

A

Mutations that give the mutant organism a growth advantage under certain conditions, such as antibiotic resistance. It allows genetic selection of mutants that can grow and others will die. Ex. antibiotic resistance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are nonselectable mutations

A

Those that may not have either an advantage or a disadvantage over the wild-type. Detection of such mutations requires examining a large number of colonies and looking for difference in various ways (screening)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is screening

A

Have to look through all the bacteria on your plate and differentiate between them

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is selection

A

Only the mutants will grow and the wild-types will die

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is replica plating

A

A method that will facilitate screening. Is useful for identification of cells with a nutritional requirement for growth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are prototrophs

A

Bacteria that do not require a specified nutrient for growth, can make everything that it needs by iteslf

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are auxotrophs

A

Bacteria that require a specified nutrient for growth that is provided in the medium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Describe the replica plating

A

First you start with a master plate of organisms that have been subjected to mutagensis on growth of complete medium. Then you press the plate onto velveteen. The Velveteen will imprint all of the colonies and you can transfer the imprints to fresh media. Put one imprint on complete medium and one imprint on minimal medium. On the complete medium all of the colonies will grow and on the minimal medium the mutants will not grow (compare)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are induced mutations

A

Mutations that are made deliberately or as a result of something in the organism’s environment, mutations that can result from exposure to radiation or chemicals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are spontaneous mutations

A

Those that occur without external intervention, can result from mistakes in the DNA replication or repair

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are point mutations

A

Mutations that change only one base pair

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are the 3 different types of point mutations

A

There can be a missense, nonsense, or silent mutation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is a missense mutation

A

A base pair change results in the incorrect amino acid being coded for and results in a faulty protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is a nonsense mutation

A

A base pair change results in a stop codon which results in an incomplete protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is a silent mutation

A

A base pair change does not result in any change of the amino acid being coded for so there is no change in the overall protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What are frameshift mutations

A

Deletions or insertions that can cause more dramatic changes. Results in the shift of the reading frame, often results in complete loss of gene function. Every codon after the deletion or insertion will be read incorrectly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is genetic engineering

A

It can involve the introduction of specific mutations (site-directed mutagensis)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What can genetic engineering be used for

A

Can be used to inactivate genes, alter ORF to produce altered function, or change the expression of gene

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is genetic engineering produced with

A

It will be produced with synthetic DNA. Synthetic primers for PCR, whole synthesis genes, and entire synthetic bacterial genome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is reversion

A

Point mutations are typically reversible. A reversion is a mutation in DNA that reverses the effects of a prior mutation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is a revertant

A

A strain in which the original phenotype is restored

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What are the two types of revertants

A

Same-site revertant and second-site revertant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Describe same-site revertant

A

Mutation is at the same site as original mutation, reverts back to the wild type sequence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Describe second-site revertant

A

Mutation is at a different site in the DNA, but still resotres wild type phenotype. Called a surpressor mutation and compensates for the effect of the original mutation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Describe how a surpressor mutation works

A

It can replace a amino acid with the same TYPE of amino acid, it won’t revert it back to the wild-type genome but this new amino acid can also fold the protein back to the same functional shape

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

How often do errors occur in DNA replication

A

10^-6 to 10^-7 per kilobase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

How are the error rates of DNA viruses

A

About 100-1000x greater because RNA repair mechanisms are rare

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What are mutagens

A

Chemical, physical, or biological agents that increase mutation rates

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What are the 3 classes of mutagens

A

Nucleotide base analogs - they resemble nucleotides. Chemicals that induce chemical modifications in DNA, and chemicals that cause frameshift mutations during replication by distorting the DNA structure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

What are biological mutagens

A

Transposons and insertion sequences

38
Q

What are the 2 main categories of mutagenic radiation

A

Non-ionizing and Ionizing radition

39
Q

Describe non-ionizing radition

A

UV radiation - purines and pyrimidines strongly absorb UV light which results in pyrimidine dimers (thymine dimers)

40
Q

Describe ionizing radiation

A

X rays, cosmic rays, and gamma rays - produce free radicals that damage macromolecules in the cell, including DNA

41
Q

What are the 3 types of DNA repair systems

A

Direct reversal, repair of single-strand and repair of double-strand damage

42
Q

Describe direct reversal in DNA repair

A

Mutated base is recognized by enzymes and repaired without referring to the other strand

43
Q

Describe repair of single-strand damage in DNA repair

A

Damaged DNA is removed and repaired using opposite strand as template. This is a method used to repair thymine dimers caused by UV radiation

44
Q

Describe repair of double-strand damage in DNA repair

A

A break in the DNA and requires error-prine repair mechanisms, this type of damage is potentially lethal

45
Q

Why is it important that DNA replication isn’t perfect

A

If DNA replication was perfect then it would prevent evolution. The mutation rate of an organism is a heritable trait. Some organisms have higher mutations rates than others

46
Q

What kind of bacteria have lower mutation rates than normal

A

Deinococcus radiodurans is 20-200 times more resistant to radiation than E.coli because of enhanced DNA repair systems.

47
Q

Describe the Ames test

A

The Ames test makes practical use of bacterial mutations to detect potentially hazardous chemicals. It can detect an increase in mutations in a bacterial strain treated with a suspected mutagen and relies on the use of an auxotrophic strain. The revertants can grow on the minimal medium and the colonies can be easily counter

48
Q

Describe the results of the Ames test

A

It relies on the reversion of an auxotrophic strain on minimal media. There will be a control plate and an experimental plate that contains the mutagen. On the control plate, only a few colonies will form due to spontaneous mutations that will revert them back to prototrophs. On the experimental plate, if the chemical it contains is a mutagen, then there will be many colonies forming because the mutations will revert a lot more back to prototrophs

49
Q

What is recombination

A

Physical exchange of DNA between genetic elements (chromosomes, plasmids, viruses, free DNA fragments)

50
Q

What is homologous recombination

A

Genetic exchange between homologoues DNA regions. Homologoues DNA regions have a common ancestor and therefore contain similar sequences and contain the same genes

51
Q

What is a recombinant

A

An organism that results from gene transfer and recombination

52
Q

What are the 3 major mechanisms for genetic recombination

A

Transformation, Transduction, and Conjugation

53
Q

Describe the process of homologous recombination

A

First an endonuclease nicks one strand of the donor DNA and SSB proteins bind to the nick to prevent it from re-attaching. Then the RecA protein will facilitate strand invasion where the hanging strand will enter the recipient DNA. The development of the cross-strand exchange occurs and results in the transfer for a section of DNA. Both of the DNA strands will be sections of one another

54
Q

What are patches.

A

Single strand transfer

55
Q

What are splices

A

Double strand transfer

56
Q

What is transformation

A

The genetic transfer process by which “naked” DNA is incorporated into a recipient cell

57
Q

Who was Fredrick Griffith and describe his experiment

A

He discovered transformation. He realized that when rats were given live S cells they were killed but when give heat-killed S cells they could live. When given a cell that lacked a capsule that would protect it from the immune system (R cells) the mouse could still live. But if you mixed the dead S-cells with the live R cells, transformation occurs and the mouse dies. Genes from the live R cells are incorporated into the dead S cells and you end up with live S cells

58
Q

What are competent cells

A

Cells that are capable of taking up DNA and being transformed

59
Q

What is transduction

A

Transfer of DNA from one cell to another by a bacteriophage (virus)

60
Q

What are the 2 types of transduction

A

Specialized and Generalized transduction

61
Q

Define generalized transduction

A

DNA from any portion of the host genome is packaged inside the virion. A defective risu particle incorporates framents of the cell’s chromosome randomly (instead of virus DNA) and the virus can be temperate or virulent

62
Q

Describe the process of generalized transduction

A

First a phage enters the cell in the lytic cycle. The phage will use the host cells metabolic activities and make many copies of its own genome. Then when the virus has to repackage itself, one of the virions accidentally packages the host cell DNA (transducing particle). Transduction will occur when this virion infects another host cell and injects the prior host cells DNA instead. Homologous recombination can occur

63
Q

What is bacterial conjugation

A

Mating. Mechanism of genetic transfer that involved cell-to-cell contact. Requires a plasmid-encoded mechanism

64
Q

What is a donor cell

A

A cell that contains the conjugative plasmid (F+ cell)

65
Q

What is a recipient cell

A

A cell that does not contain the conjugative plasmid (F-cell)

66
Q

What is the F plasmid

A

The fertility plasmid. It is a short circular DNA molecule. Contains a oriV for replication and oriT for DNA transfer. It contains several transposable elements that allow the plasmid to integrate into the host chromosome and contains tra genes that encode the transfer functions

67
Q

What is the sex pilus

A

It is essential for bacterial conjugation and is only produced by the donor cell and is encoded by genes on the F plasmid

68
Q

What is necessary for DNA transfer by conjugation

A

DNA synthesis.

69
Q

How is the DNA synthesized in conjugation

A

The DNA is synthesized by rolling circle replication starting at the oriT

70
Q

Describe the process of conjguation

A

The two bacterial cells (donor and recipient) are connected by a pilus. The F plasmid is nicked in on strand. The transfer of one strand from the F+ cell to the F- cell occurs (rolling circle replication) and the F plasmid is simultaneously replicated in the F+ cell. Then synthesis of the complementary strand begins in the recipient cell. After completion of DNA transfer and synthesis the cells separate. Both are F+ cells in the end

71
Q

What is an episome

A

Something that can integrate into the host chromosome (F plasmid)

72
Q

What are F+ cells

A

Cells possessing a nonintegrated F plasmid

73
Q

What are Hfr cells

A

Cells possessing an integrated F plasmid (high frequency of recombination).

74
Q

What is the importance of Hfr cells

A

The integrated F plasmid causes transfer for chomosome, it results in high rates of gene transfer and genetic recombination between genes on the donor chromosome and those of the recipient cell

75
Q

How does the F plasmid become integrated

A

Insertion sequences (IS) are mobile DNA elements that are present in both the F plasmid and the E.coli chromosome. Homologous recombination results in integration

76
Q

Describe the process of how the F plasmid becomes integrated into the chomosome

A

Both the F plasmid and the chromosome have insertion seqeunces. The insertion sequences will break apart from their respective strand and the F plasmid can integrate itself entire into the chromosome by connecting at the insertion sequences. Results in two copies of the insertion sequence on the chromosome

77
Q

Describe the transfer of chromosomal DNA by conjugation

A

Between an Hfr cell and a F- cell. The F plasmid is nicked in one strand and the transfer of F is followed by the chromosomal DNA. This results in part of the chromosomal DNA being brough into the recipient cell.

78
Q

What is merodiploid

A

Partial diploid. A bacterial strain that carries two copies of a chromosomal region. DNA region can be introduced into cell by transformation, trasnduction, or conjugation

79
Q

What is complementation

A

A functional copy of a gene compensates for a defective copy of the gene in the same cell. Restoring of the wild type phenotype

80
Q

What are complementation tests used for

A

They are used to determine if two mutations are in the same gene or different genes. If an introduced DNA fragment compensates for a mutant gene, then it “complements” the mutation and must contain a wilf-type copy of the mutant gene. If the introduced DNA contains a mutation in the same gene, it cannot complement

81
Q

Describe an example of complementation

A

Say we have a chromosome with a mutation on the gene that causes the gene to be nonfunctional. (Gene A works but Gene B doesn’t). Then you have another organism with the same phenotype but you’re not sure if its the same mutation or not. You can bring a stretch of DNA from one organism to another and if both of the organisms have the mutation in the same gene then you will fail to complement. But if the other DNA has (Gene A doesn’t work and Gene B works) then both Gene A and Gene B will end up working due to complementation

82
Q

Describe gene transfer in Archaea

A

Archaea usually contain a circular chromosome like bacteria and examples of transformation, trasnduction, and conjugation have been found in Archaea.

83
Q

What are transposable elements

A

Discrete segments of DNA that move as a unit from one location to another. Can be found in all 3 domains of life They are selfish DNA that are parasitic, only encodes genes for its own propagation and can move from one location to another on a chromosome, to a pahge genome, or to a plasmid

84
Q

What is transposition

A

The process of transposable elements moving. Frequency of transposition is usually very low. Low transcription frequency is selected for during evolution to limit international mutations caused by transposons

85
Q

What are the 2 main types of transposable elements in bacteria

A

Insertion sequences and Transposons

86
Q

What do transposable elements carry on their gene

A

They carry genes encoding for transposase, the enzyme required for hopping around. They also have DNA inverted repeats at their ends and transposons carry additional genes

87
Q

Describe an insertion sequence (IS)

A

Are the simplest transposable element. About 1000 nucleotides long and the inverted repeats at the end are about 10-50 base pairs. The only gene carried by the IS is for transposase. The transposase recognizes the inverted repeats on the DNA.

88
Q

Where are insertion sequences found

A

They can be found in plasmids and chromosome for Bacteria and Archaea, and also in bacteriophage genomes

89
Q

What is transposase

A

The enzyme that catalyzes transposition. allows the DNA to move around

90
Q

Describe transposons

A

Are larger than insertion sequences and carry additional DNA between inverted repeats. Most transposons carry antibiotic resistance genes. Transposons allow for rapid exchange of antibiotic resistance genes among bacterial populations

91
Q

What happens during the insertion of a transposable elements

A

Insertion of a transposable element (IS or Tn) often generates a duplication of the target seqeunce, its a result of the transposase mechanism

BIMM 120 (17 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions