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Genetics > Gene Function, Phenotype, and Mutation > Flashcards

Gene Function, Phenotype, and Mutation Flashcards

1
Q

Affect a diploid phenotype when present in two copies

A

recessive

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2
Q

Most loss of function alleles

A

recessive

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3
Q

affect a diploid as a single copy

A

dominant

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4
Q

most gain of function alleles

A

dominant

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5
Q

occurs when one functional copy of a gene is not enough to carry out function (example of loss of function dominant allele)

A

haploinsufficiency

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6
Q

the nonfunctional copy interferes with the functional copy (example of loss of function dominant allele)

A

dominant negative

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7
Q

change of single nucleotide: silent, missense, or nonsense

A

substitutions

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8
Q

insertions and deletions can result in

A

frameshifts

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9
Q

reverse the effects of a mutation in another gene

in tRNAs can prevent DNA changes from altering protein sequence

A

suppressor mutations

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10
Q

Occur through cellular error or biochemical variation
- tautomeric shift
- replication error or slippage
- reactions in cellular environment
- transposons

A

spontaneous mutations

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11
Q

Occur due to extracellular influence from toxin, chemical, radiation, etc
- Base analogs
-alkylating agents and intercalating agents
- UV radiation
Ionizing radiation

A

Induced mutations

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12
Q

Change from one purine/pyrimidine pair to the other purine/pyrimidine pair

A/T <–> G/C
T/A <–> C/G

A

Transition

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13
Q

Change between a purine/pyrimidine pair and a pyrimidine/purine pair

A/T <–> T/A
G/C <–> C/G
A/T <–> C/G
G/C <–> T/A

A

Transversion

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14
Q
  • can lead to incorporation of the wrong complementary base during DNA replication
  • Bases exist in one of two forms and a small minority of bases exist as alternate tautomers
  • mismatches due to tautomeric shifts can be corrected by DNA polymerase proofreading
A

Spontaneous Mutation: tautomeric shift

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15
Q
  • repetitive sequences can confuse DNA polymerase III and it can “lose its place”
  • spontaneous deletions/insertions may arise in repetitive DNA during replication
A

Spontaneous Mutation: DNA Replication Slippage

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16
Q
  • Ex: Bromodeoxyuridine (BrdU)
  • increases rate of tautomeric shift and thus adding BrdU to cells increases the chance of mismatch mutations during replication
A

Induced Mutation: Chemical mutagens- Base Analogs

17
Q

Chemical agent that can directly alter chemical structure of nitrogenous bases within DNA, causing them to mispair during replication (i.e. ethyl methanesulfonate (EMS) alkylates guanines GC -> AT)

A

Induced Mutation: Chemical Mutagens - Base Modifiers

18
Q

Distort DNA double-helix, causing DNA polymerase slippage and insertion/ deletion mutations

ex: ethidium bromide (agarose gels), acridine, Proflavin

A

Induced Mutation: Chemical Mutagens- Intercalating Agents

19
Q

Causes thymine-thymine dimers - bulge in DNA helix

Deletion in opposite strand during DNA replication

may stall DNA replication and cause cell death

A

Induced Mutation: UV irradiation

20
Q

Strong enough to break phosphodiester bonds –> double-strand breaks in DNA

A

Stronger Ionizing Radiation (X-rays, Gamma rays, cosmic rays)

21
Q

Determines if agent is mutagenic and if so, what type of mutations it can cause

A

Ames Test

22
Q
  1. auxotrophic mutation (his- cannot grow in absence of histidine)
  2. Different strains carry different mutations in the his gene that can be used to assay for reversion of substitutions and frameshifts
  3. Uniformly cover plate that lacks histidine with bacteria
  4. Incubate to promote colony growth
  5. Control: spontaneous his+ revertant colony
  6. Experiment: Potential mutagenic compound added, induced his+ revertant colonies
A

Steps of Ames Test

23
Q

Create a mutant phenotype and identify the causative mutation

A

Forward Genetics

24
Q

Target a sequence for mutation and observe phenotype

A

Reverse genetics

25
Q
  1. What genes are required for a particular biology process?
  2. Treat organism/ cells with a mutagen to induce random mutations
  3. Screen organisms/cells for defects in process of interest (phenotype)
  4. Map/clone the mutation to identify a gene required for the process of interest
  5. Study the gene/protein to determine how it works in the process of interest
A

Forward genetic screens

26
Q

Corrects replication errors missed by DNA Polymerase III proofreading

1) recognition of mismatch
2) recruitment of proteins
3) excision of DNA strand containing wrong nucleotide
4) resynthesis of excision gap by DNA pol using remaining DNA strand as template
5) ligation

A

Mismatch Repair (MMR)

27
Q

Bacteria: methylation
Eukaryotes: interaction of repair proteins with DNA replication machinery

A

How a strand with errors is identified with a mismatch (MMR)

28
Q

Pathways that remove damaged base(s) and DNA polymerase and ligase replace the excised bases and seal the nick

Damage can be detected by proteins that survey the genome, or damage can be detected during transcription when RNA polymerase stalls at a lesion or adduct

A

Base Excision Repair (BER) and Nucleotide Excision Repair (NER)

29
Q

Can be induced by high ionizing radiation (gamma rays, cosmic rays) or through oxidative stress in the cell

A

Double-Strand Breaks (DSBs)

30
Q

DSBs can be repaired through…

A

Homologous Recombination (HR) or Non-Homologous End Joining (NHEJ)

31
Q

no template is used for repair

repair may not be accurate- can lead to genome rearrangements

A

NHEJ

32
Q

homologous chromosome is used as a template for extending the broken chromosome beyond the break point

strands can separate and DNA is filled-in and ligated by DNA pol I and ligase

can result in exchange of DNA between homologous chromosomes (DSB repair) or copying DNA from one chromosome to another (synthesis-dependent strand annealing)

Can cause a crossover

A

HR

33
Q

Introduce DNA to a cell that contains a selectable marker flanked by sequences homologous to a target

A

Target Gene Inactivation (Knockout)

Genetics (9 decks)

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