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Genetics > Chapter 19 > Flashcards

Chapter 19 Flashcards

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Biology 101 flashcards
1
Q

Mutation

A

A heritable change in the genetic material

The structure of dna is changed permanently and can be passed to daughter cells

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2
Q

Point mutation

A

A change in a single base pair within the DNA

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3
Q

Base substitution

A

One base is substituted for another

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4
Q

Transition

A

A mutation of a pyrimidine to another pyrimidine such as C to T or purine by purine A to G

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5
Q

Transversion

A

Purine and pyrimidine are Interchanged causing mutation from such as T to G

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6
Q

Silent mutations

A

Those that do not alter the amino acid sequence of the polypeptide even though the base sequence had changed

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7
Q

Missense mutations

A

Base substitutions for which an amino acid change does result

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8
Q

Nonsense mutations

A

A change from a normal codon to a stop codon

Terminating the translation of the polypeptide earlier than expected, truncating polypeptide

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9
Q

Frameshift mutations

A

The addition or deletion of a number of nucleotides that is not divisible by 3

Resulting in a completely different amino acid sequence downstream from the mutation

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10
Q

Neutral mutation

A

A missense mutation that has no detectable effect on protein function

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11
Q

Up promoter mutations

A

Promoter mutations that increase transcription

More like the consensus sequence

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12
Q

Down promoter mutation

A

Decreases the affinity for transcription factors and decreasing the transcription rate

Promoter becomes less like the consensus sequence

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13
Q

Wild type

A

Relatively prevalent genotype within a natural population

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14
Q

Mutant allele

A

Rare mutation in a population

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15
Q

Reversion

A

Reverse mutation, that changes a mutant allele back to a wild type allele

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16
Q

Deleterious mutation

A

Decreases the chance of survival and reproduction

Lethal mutation: results in the death of a cell or organism

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17
Q

Beneficial mutation

A

Enhances the survival or reproductive success of an organism

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18
Q

Conditional mutants

A

Phenotype is only affected under a defined set of conditions for example temperature

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19
Q

Suppressor mutations

A

A second mutation that affects the phenotypic expression of a first mutation. Differs from a reversion because it occurs at a different site in the DNA from the first mutation

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20
Q

Intragenic suppressor

A

When the second mutation site is within the same gene as the first mutation. This type of suppressor often produces a change in protein structure that compensates for abnormality and protein structure caused by the first mutation

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21
Q

Intervening suppressor

A

A suppressor mutation that occurs in a different gene from the first mutation. The suppressor mutations usually involve a change in the expression of one gene that compensates for loss of function mutation affecting another gene.

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22
Q

Breakpoint

A

A region where to chromosome pieces break and re-join with other chromosome pieces, occurs within a gene. Most likely to inhibit gene function.

23
Q

Position effect

A

A gene may be moved next to regulatory sequences for a different gene, such as silencers or enhancers, that influence the expression of the relocated gene. Or a chromosome or rearrangement may reposition a gene from a less condensed or euchromatic chromosome, where it is active, to a very highly condensed or heterochromatic chromosome.

24
Q

Germ line mutation

A

Can occur directly in a sperm or egg cell, or it can occur in a precursor cell that produces the gametes. All cells of the resulting offspring will contain the mutation and to future generations.

25
Q

Somatic cells

A

All cell except germ line cells

26
Q

Somatic mutation

A

Somatic cells can mutate at the early or late stages of development

The size of the affected region depends on the timing of the mutation, the earlier the mutation the larger the affects

27
Q

Genetic mosaic

A

An individual that has somatic regions that differ genotypically from each other

28
Q

Replica plating

A

A technique developed by Joshua and Esther in the 1950s. To test whether mutations are random events using a wild type strain of E. coli and T1 bacteriophage

29
Q

Random mutation theory

A

Mutation is a random process. It can occur in energy and does not require the exposure in organism to environmental condition that causes specific types of mutations to happen.

30
Q

Hot spots

A

Certain regions of a gene that are more likely to mutate then other regions

31
Q

Spontaneous mutations

A

Changes in DNA structure that result from natural biological or chemical processes

32
Q

Induced mutations

A

Caused by environmental agents

33
Q

Depurination

A

Removal of a purine (adenine or guanine) from the DNA

34
Q

Apurinic site

A

When the unstable covalent bond between deoxyribose and a purine bases undergoes a spontaneous reaction with water that releases the base from the sugar

DNA repair enzymes can fix this

Replication of this site may lead to a new mutation

35
Q

Deamination if cytosines

A

The removal of an amino group from the cytosine base. This produces uracil. Being that DNA repair enzymes cannot recognize you were still as an inappropriate base within DNA to remove it but if this repair does not take place then a mutation may result.

36
Q

Tautomeric shift

A

When tautomers (bases) That exist in Keto and Enol or amino and imino forms. Bacon into convert by a chemical reaction that migrates a hydrogen item and switches a single bond and adjacent double bond. Doesn’t adhere to AT/GC rule which may lead to a mutation

37
Q

Reactive oxygen species

A

Examples are hydrogen peroxide, super oxide, and hydroxyl radical. These are products of oxygen metabolism in all aerobic organisms. And eukaryotes it is a unwanted byproduct of energy production in mitochondria. If they accumulate they can damage cellular molecules, including DNA proteins and lipids. UsuallyEnzymes prevent this accumulation but if not this can cause a variety of medical conditions. Antioxidants help.

38
Q

Oxidative stress

A

An imbalance between the production of ROS and an organisms ability to break them down. If ROS over accumulate oxidative DNA damage is a harmful consequences which refers to changes in DNA structure.

39
Q

Trinucleotide repeat expansion

A

A repeated sequence of three nucleotides can readily increase in number from one generation to the next. People with this disorder The length of a tri-nucleotide repeats has increased above a certain critical size thereby causing disease symptoms.

Anticipation: when these disorders have the unusual feature of progressively worsening severity in future generations

40
Q

Mutagens

A

Agents known to alter the structure of DNA and thereby cause mutations

Covalently modifying the structure of bases

Alkylating agents: nitrogen mustard and ethyl methanesulfonate

Acridine dyes cause frameshift mutations

Tautomeric shifts of 5 Bromouracil and 2 aminopurine changes AT to GC

41
Q

High exposure to radiation (X-ray)

A

Produces chemically reactive molecules known as free radicals. These molecules can alter the structure of DNA. Resulting in deletions, oxidized bases, single-stranded nicks in DNA, cross-linking, and chromosomal breaks.

42
Q

Mutation rate

A

The likelihood that a gene will be altered by a new mutation, given by the number of new mutations in a given gene per cell generation

43
Q

Mutation frequency

A

The number of mutant genes divided by the total number of copies of that gene within a population

44
Q

Ames test

A

Test developed by Bruce Ames, Uses strains of bacterium that cannot synthesize the amino acid histidine. The test monitors the rate at which the second mutation occurs, indicating whether an agent increases the mutation rate above the spontaneous rate

45
Q

DNA repair steps

A

1st- One or more proteins in the DNA repair system detect an irregularity in DNA structure

2nd- The abnormality is removed by the action of DNA repair enzymes.

3rd- Normal DNA is synthesized via DNA replication enzymes

46
Q

Photolyase

A

Recognizes thymine dimers (UV Light) and splits them, which returns the DNA to its original condition. This mechanism requires light which is known as photoreactivation. Containing two light sensitive cofactors.

47
Q

Alkytransferase

A

Can remove methyl or ethyl groups from guanine bases that have been mutagenized by alkylating agents such as nitrogen mustard and EMS

Can only be used once

48
Q

Base excision repair (BER)

A

Primarily responsible for illuminating non-helix distorting changes that affect the structure of individual basis. Involves the function of a category of enzymes known as DNA-N glycosylases

Important for the repair of oxidative DNA damage

49
Q

Nucleotide excision repair

A

Used to repair bulky, helix distorting lesions. Can repair thymine diners, Chemically modified bases, missing bases, and certain types of cross links. Removes damaged nucleotides and the intact strand is used as a template for resynthesis of a normal complementary strand

50
Q

Base pair mismatch

A

When an incorrect nucleotide is added to the growing strand by mistake

Mismatch repair system: an additional DNA repair systems that detect base pair mismatches and fix them

51
Q

Homologous recombination repair

A

When homologous DNA strands usually from a sister chromatid, are used to repair a DSB in the other sister chromatid

52
Q

Nonhomologous end joining

A

The two broken ends of DNA are simply pieces back together

Disadvantage is that NHEJ May result in a small deletion in the region that has been repaired

53
Q

Translesion synthesis

A

The synthesis of DNA over a template that harbors some type of DNA damage. This occurs via lesion-replicating polymerases

Low fidelity

Error prone replication (high mutation rate)

Genetics (9 decks)

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