Chapter 19

Question 1

Mutation

Answer 1

A heritable change in the genetic material

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

Question 2

Point mutation

Answer 2

A change in a single base pair within the DNA

Question 3

Base substitution

Answer 3

One base is substituted for another

Question 4

Transition

Answer 4

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

Question 5

Transversion

Answer 5

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

Question 6

Silent mutations

Answer 6

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

Question 7

Missense mutations

Answer 7

Base substitutions for which an amino acid change does result

Question 8

Nonsense mutations

Answer 8

A change from a normal codon to a stop codon

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

Question 9

Frameshift mutations

Answer 9

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

Question 10

Neutral mutation

Answer 10

A missense mutation that has no detectable effect on protein function

Question 11

Up promoter mutations

Answer 11

Promoter mutations that increase transcription

More like the consensus sequence

Question 12

Down promoter mutation

Answer 12

Decreases the affinity for transcription factors and decreasing the transcription rate

Promoter becomes less like the consensus sequence

Question 13

Wild type

Answer 13

Relatively prevalent genotype within a natural population

Question 14

Mutant allele

Answer 14

Rare mutation in a population

Question 15

Reversion

Answer 15

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

Question 16

Deleterious mutation

Answer 16

Decreases the chance of survival and reproduction

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

Question 17

Beneficial mutation

Answer 17

Enhances the survival or reproductive success of an organism

Question 18

Conditional mutants

Answer 18

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

Question 19

Suppressor mutations

Answer 19

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

Question 20

Intragenic suppressor

Answer 20

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

Question 21

Intervening suppressor

Answer 21

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.

Question 22

Breakpoint

Answer 22

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

Question 23

Position effect

Answer 23

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.

Question 24

Germ line mutation

Answer 24

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.

Question 25

Somatic cells

Answer 25

All cell except germ line cells

Question 26

Somatic mutation

Answer 26

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

Question 27

Genetic mosaic

Answer 27

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

Question 28

Replica plating

Answer 28

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

Question 29

Random mutation theory

Answer 29

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.

Question 30

Hot spots

Answer 30

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

Question 31

Spontaneous mutations

Answer 31

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

Question 32

Induced mutations

Answer 32

Caused by environmental agents

Question 33

Depurination

Answer 33

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

Question 34

Apurinic site

Answer 34

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

Question 35

Deamination if cytosines

Answer 35

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.

Question 36

Tautomeric shift

Answer 36

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

Question 37

Reactive oxygen species

Answer 37

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.

Question 38

Oxidative stress

Answer 38

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.

Question 39

Trinucleotide repeat expansion

Answer 39

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

Question 40

Mutagens

Answer 40

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

Question 41

High exposure to radiation (X-ray)

Answer 41

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.

Question 42

Mutation rate

Answer 42

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

Question 43

Mutation frequency

Answer 43

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

Question 44

Ames test

Answer 44

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

Question 45

DNA repair steps

Answer 45

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

Question 46

Photolyase

Answer 46

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.

Question 47

Alkytransferase

Answer 47

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

Question 48

Base excision repair (BER)

Answer 48

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

Question 49

Nucleotide excision repair

Answer 49

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

Question 50

Base pair mismatch

Answer 50

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

Question 51

Homologous recombination repair

Answer 51

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

Question 52

Nonhomologous end joining

Answer 52

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

Question 53

Translesion synthesis

Answer 53

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)