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Prokaryotic Molecular Genetics > Mutation > Flashcards

Flashcards in Mutation Deck (35):

Definition: Mutant

Organism that is direct offspring of wild-type but is different


Definition: Strain

Organisms of the same species isolated from nature that have different properties (because it is no possible to know which the mutant)


Definition: Phenotype

All the observable properties of an organism


Definition: Genotype

The actual sequence of an organism's DNA


Definition: Mutation

An heritable change in DNA sequence


Definition: Allele

Different forms of the same gene. Bacteria are haploid therefore it has one allele


Nomenclature: lac

lactose metabolism


Nomenclature: his

histidine biosynthesis


Nomenclature: dna

DNA synthesis


Nomenclature: pol

DNA polymerase


Nomenclature: uvr

UV repair


Nomenclature: rec



Letters distinguish different genes that affect or function in the same process. Give an example.

lacZ, lacY, lacA ; hisA, hisB, hisC (all undercase should be italicized)


Protein products of genes are given the same name. (but it is not "italicized" and the first letter is capitalized) Give an example

RecA ; DnaA


What are the consequences of mutations?

-Some are harmless
-Some may cause a change in phenotype
-Some are bad
-Some are lethal


Bac Phenotypes: Prototroph and auxotroph. (based on growth on particular media)

An auxotroph can not make or lacks the ability to grow on a particular nutrient. [Ex. A mutant strain that has lost the ability to synthesize its own supply of tryptophan is a Trp auxotroph and is designated Trp]


Bac Phenotypes: Ability to utilize substrates (based on growth on particular media)

The ability to utilize a particular carbon and energy source can also be used as a phenotype. [Ex. A strain harboring a mutation rendering it unable to utilize the sugar galactose is galactose-, of Gal-]


Bac Phenotypes: Antibiotic resistance (based on growth on particular media)

The ability to grow in the presence of an antibiotic


Bac Phenotypes: Other markers (2 examples) (based on growth on particular media)

Colony morphology and resistance to phage.


Auxotrophic mutants can be isolated because?

They have mutations in genes whose products are required under certain conditions.


What are the conditions that DNA changes would be lethal?

-Temperature sensitive mutants
-Cold sensitive mutants
-Nonsense mutations


What are the two types of Temperature-sensitive mutation from DNA changes?

*Permissive temperature: the protein function
*Nonpermissive temperature: higher temperature


Lethal DNA mutation def: Temperature-sensitive mutants

Change an amino acid of the protein so that protein no longer function at high temperature but still function at lower temp


Lethal DNA mutation def: Cold sensitive mutants

Cells with proteins that fail to function at lower temperature. The mutation occurs in genes whose products must form a large complex (ex. Ribosome_
-At higher temp, the mutated protein can entered in the complex, but it will not be able to do so a lower temperature


Lethal DNA mutation def: Nonsense mutations

Mutation that change a codon in a gene to one of the three nonsense codons (UAA, UAG, or UGA)
-Translation of the gene doesn't stop unless the cell has a "nonsense suppressor" tRNA


Resistance: Luria and Delbruck experiment demonstrates that in bacteria, genetic mutations arise in the absence of selection, rather than being a response to selection. What are the two types of hypothesis and their definitions

1. Random mutations: If it is correct among of mutated will varied in all cultures, depending of when the mutation occur
2. Direct change: If it is correct each bacterium will have same chance of becoming a mutant


T or F: Random mutations hypothesis is correct

True; If correct among the mutated will vary in all cultures, depending of when the mutation occur.


What are the two ways that could cause mutations?

1. Environmental insults
2. Errors in DNA replication


Mutations are?

Permanent changes in the DNA sequence that are inherited


Depending upon the nature of the mutation, they can what?

Be expressed as abnormal proteins


Depending upon the function of the protein, mutations that affect that protein might what?

Result in an easily observable phenotypic change


Some mutations (phenotypes) only appear under what kind of conditions?

Only under certain conditions, such as exposure to a certain environmental agent or condition


Base Pair changes have 4 different type that can cause it. What are they?

1. Transitions
2. Transversions
3. Missense mutations
4 Nonsense mutations


Base pair changes are one of the types of mutations. What are the other 4?

1. Frameshift mutations
2. Deletion mutations
3. Inversion mutations
4. Tandem duplications


Mispairing during the replication can what?

Lead to a base pair change in DNA