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CYTOGEN FINALS > PRE LEC 3: GENE MUTATION > Flashcards

PRE LEC 3: GENE MUTATION Flashcards

1
Q
  • Alteration in DNA sequence that is rare in
    the population
  • Typically affects phenotype
  • base - pair change in any part of the DNA molecule
  • are recessive and cause a loss-of-function
A

GENE MUTATION

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2
Q

refers to theprocess of altering a DNA sequence.

A

MUTATE

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3
Q

EFFECTS OF MUTATION
- genes’ product is reduced or absent

A

“loss-of-function”

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4
Q

EFFECTS OF MUTATION
- gene’s activity changes
- tend to be dominant and are also called “TOXIC”

A

“gain-of-function”

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5
Q
  • the differences between organisms caused by alternates form of DNA
A

GENETIC VARIATION

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6
Q

SOURCES OF GENETIC VARIATION
- GENOTYPE
- alteration/change at the DNA or chromosome level.

A

MUTATION

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7
Q

SOURCES OF GENETIC VARIATION
- “many forms”
- alteration in DNA sequence that is common in the population
- Do not severely affect the phenotype
- Short tandem repeats (microsatellites):

A

POLYMORPHISM

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8
Q

: short repeating units (2-6 nucleotides), vary in number among individuals and is often used in DNA
profiling and paternity testing

A

Short tandem repeats (microsatellites)

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9
Q
  • refers to phenotype; describes an allele.
  • depends upon how the mutation affects the gene’s product or activity, and usually connotes an abnormal or unusual characteristic.
  • may also be a rare variant that is nevertheless “normal,” such as red hair.
A

MUTANT

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10
Q

___________ mutation treats HIV infection

A

CCR5

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11
Q

o Occurs in the gametes during DNA
replication before meiosis
o All cells will have the mutation
- are transmitted to the next generation of individuals.

A

germline mutation

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12
Q
  • occurs in ANY CELL IN THE BODY except germ cells
  • happens during DNA replication before mitosis
  • passed to the next generation of cells but NOT PASSED TO ALL CELLS
  • has “somatic mosaicism”
A

somatic mutation

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13
Q

occur in cells that divide often, such as skin and
blood cells

A

Somatic mosaicism

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14
Q

CAUSES OF MUTATION
- Changes in the nucleotide sequence of gene with no known cause
- Generally assumed to be accidental
- Originates as an error in DNA replication, may be due to the lack of DNA repair
- also manifests as “gonadal mosaicism”

A

Spontaneous mutation

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15
Q

likelihood of a gene to undergo mutation in a single generation or in a single gamete

A

Spontaneous mutation rate

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16
Q

where mutations are more likely to occur,
where sequences are repetitive
▪REPETITIVE SEQUENCES: symmetrical:
may confuse replication enzymes

A

Mutational hotspots

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17
Q

CAUSES OF MUTATION
- Result from the influence of external factors (mutagens), such as exposure to CHEMICAL/RADIATION
- may be the result of either natural/artificial agents

A

Induced mutation

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18
Q
  • agents of mutations
A

MUTAGENS

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19
Q

MUTAGENS

A
  • Base analogs,
  • alkylating agents,
  • intercalating agents,
  • adduct-forming agents (acetaldehyde
    and heterocyclic amines)
  • UV LIGHT
  • IONIZING RADIATION
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20
Q
  • base pairing mutation
  • Base analogs,
  • alkylating agents,
  • intercalating agents,
  • adduct-forming agents (acetaldehyde
    and heterocyclic amines)
A

CHEMICAL MUTAGENS

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21
Q

point mutation, most common mutagen
➢ UV light, sunlight, and ionizing radiation

A

Radiation mutagens

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22
Q

can be found inserted into our DNA
➢ Viruses and transposable elements

A

Biological mutagens

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23
Q

caused by environmental pollutants and
lifestyle factors
➢ Tobacco smoke and alcohol

A

Environmental mutagens

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24
Q

Common products containing mutagens

A
  • Hair dye
  • Smoked meats
  • Certain flame retardants in children’s sleepwear
  • Food additives
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25
Q
  • Developed by DR. BRUCE ARMES in 1970s
  • commonly used method that uses bacteria (Salmonella typhimurium) to test if the chemical can cause mutation in the DNA of the test organism
  • Indication: produces a measurable increase in the number of colonies
A

Ames Test

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25
Q

Accidental exposure to mutagens:

A
  • Workplace contact before danger is known
  • Industrial accidents
  • Medical treatments (chemotherapy and
    radiation)
  • Exposure to weapons that emit radiation
  • Natural disasters that damage RADIATION EMITTING EQUIPMENT
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26
Q

Natural exposure to mutagens:

A
  • Natural environment sources of radiation (cosmic rays, sunlight, & radioactive substances)
  • Medical X-rays and occupational radiation hazards (ionizing radiation)
  • Job sites with increased radiation exposure (weapon facilities, research lab, health care facilities, nuclear power plants, & certain manufacturing plants)
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27
Q

Types of Mutations
* Change of one base pair to another in a
DNA molecule
a. Transition
b. Transversion
c. Missense
d. Nonsense
e. Silent
f. Splice-site

A

Point Mutations

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28
Q

Point Mutations
: purine replaces PURINE (A-G) and pyrimidine replaces pyrimidine (T-C)
a. Transition
b. Transversion
c. Missense
d. Nonsense
e. Silent
f. Splice-site

A

TRANSITION

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29
Q

POINT MUTATIONS
- purine replaces a PYRIMIDINE (A-T; C-G) or vice versa
a. Transition
b. Transversion
c. Missense
d. Nonsense
e. Silent
f. Splice-site

A

TRANSVERSION

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30
Q

POINT MUTATIONS
- SUBSTITUTION in the codon that codes for a DIFFERENT amino acid
a. Transition
b. Transversion
c. Missense
d. Nonsense
e. Silent
f. Splice-site

31
Q

POINT MUTATIONS
- CHANGE in codon that codes for a stop codon, protein is shortened that leads to premature termination of the translation process
a. Transition
b. Transversion
c. Missense
d. Nonsense
e. Silent
f. Splice-site

32
Q

POINT MUTATIONS
- SUBSTITUTION in the codon that
codes for the SAME amino acid
a. Transition
b. Transversion
c. Missense
d. Nonsense
e. Silent
f. Splice-site

33
Q

POINT MUTATIONS
- ALTERS A SITE in the junctions
of exons and introns, happens after the
mRNA processing
a. Transition
b. Transversion
c. Missense
d. Nonsense
e. Silent
f. Splice-site

A

SPLICE-SITE

34
Q

Types of Mutations
* Disrupts the reading frame during translation, causing a shift in the way codons are read
* Results to nonfunctional proteins
a. Deletion mutation
b. Insertion mutation
- Tandem duplication

A

Frameshift Mutation

35
Q

Frameshift Mutation
- REMOVAL of one or more nucleotides

A

Deletion mutation

36
Q

Frameshift Mutation
- ADDITION of one or more nucleotides

A

Insertion mutation

37
Q

FRAMESHIFT MUTATION: INSERTION MUTATION
- insertion of two complete copies of a gene next to
each other
Ex. Charcot-Marie-Tooth disease

A

Tandem duplication

38
Q

TYPES OF MUTATIONS
* DNA sequence very similar to the sequence of a protein-encoding gene
* Not translated into protein, but is transcribed resulting to nonfunctional proteins

A

Pseudogenes

39
Q

result from a CROSSOVER BETWEEN the WORKING GENE and its PSEUDOGENE, resulting to a fusion gene

A

Gaucher disease

40
Q

Types of Mutations
* Disrupts the site they jump into by SHUTTING OFF TRANSCRIPTION OF THE GENE they jump into, or alters the reading frame if not a multiple base of 3

A

Transposons “jumping genes”

41
Q

Types of Mutation
* Segment of DNA within a gene undergoes EXPANSION resulting in the amplification of a repetitive DNA sequence
* Small part of the DNA sequence is copied and added to the gene
* Anticipation: specific DNA sequence in the gene EXPANDS in size across generations, worsening symptoms

A

Expanding Repeats

42
Q

Type of Mutation
* Specific DNA sequence that VARIES IN NUMBER OF COPIES in individuals
* Types: duplication, deletions, and triplet repeats
* Common among people who have behavioral disorders (ADHD, autism, and schizophrenia)

A

Copy Number Variants

43
Q
  • Different mutations at the same site in a
    gene can have different effects
  • Can cause anemia without sickling, or cause CYANOSIS
  • Considered “clinically silent”
A

Globin gene mutations

44
Q

Mutation in the b-globin Gene
o First genetic illness understood at the molecular level
o Cause: substitution of Valine from Glutamic Acid at the 6th codon of the b-globin chain
o Effect: Valine increases the frequency of hemoglobin molecules in low-oxygen conditions

A

Sickle cell disease

45
Q

Mutation in the b-globin Gene
o Reduced production of either alpha or
beta chains
a. Thalassemia major (alpha thalassemia)
b. Thalassemia minor (beta thalassemia)

A

Thalassemia

46
Q

severe form, homozygous mutation in the gene

A

Thalassemia major (alpha thalassemia):

47
Q

milder form, heterozygous mutation in the gene

A

Thalassemia minor (beta thalassemia)

48
Q
  • Major component of connective tissue
49
Q

MUTATION: Mutations in any of three genes (COL4A3, COL4A4, COL4A5) affect type IV collagen, which disrupts tissue boundaries.
SIGNS AND SYMPTOMS: Deafness and inflamed kidneys

A. Alport syndrome
B. Chondrodysplasia
C. Dystrophic epidermolysis bullosa
D. Ehlers-Danlos syndrome
E. Osteoarthritis
F. Osteogenesis imperfecta type I
G. Stickler syndrome

A

Alport syndrome

50
Q

MUTATION: Deletion, insertion, or missense mutation replaces Gly with bulky amino acids in COL2A1 type II collagen gene
SIGNS AND SYMPTOMS: Stunted growth, deformed joints

A. Alport syndrome
B. Chondrodysplasia
C. Dystrophic epidermolysis bullosa
D. Ehlers-Danlos syndrome
E. Osteoarthritis
F. Osteogenesis imperfecta type I
G. Stickler syndrome

A

Chondrodysplasia

51
Q

MUTATION: Mutation in “COL7A1 gene” that encodes type VII collagen breaks down fibrils that attach epidermis to dermis.
SIGNS AND SYMPTOMS: Skin blisters upon any touch

A. Alport syndrome
B. Chondrodysplasia
C. Dystrophic epidermolysis bullosa
D. Ehlers-Danlos syndrome
E. Osteoarthritis
F. Osteogenesis imperfecta type I
G. Stickler syndrome

A

Dystrophic epidermolysis bullosa

52
Q

MUTATION: DIVERSE mutations in at least a dozen genes affect collagens or the molecules to which they bind
SIGNS AND SYMPTOMS: Stretchy, easily scarred skin, lax joints

A. Alport syndrome
B. Chondrodysplasia
C. Dystrophic epidermolysis bullosa
D. Ehlers-Danlos syndrome
E. Osteoarthritis
F. Osteogenesis imperfecta type I
G. Stickler syndrome

A

Ehlers-Danlos syndrome

53
Q

MUTATION: MISSENSE mutation in “α1” collagen gene (COL1A1) substitutes Cys for Arg.
SIGNS AND SYMPTOMS: Painful joints

A. Alport syndrome
B. Chondrodysplasia
C. Dystrophic epidermolysis bullosa
D. Ehlers-Danlos syndrome
E. Osteoarthritis
F. Osteogenesis imperfecta type I
G. Stickler syndrome

A

Osteoarthritis

54
Q

MUTATION: INACTIVATION of “α1” COLLAGEN GENE (COL1A1 or COL1A2) reduces number of collagen triple helices by 50%
SIGNS AND SYMPTOMS: Easily broken bones; blue eye whites; deafness

A. Alport syndrome
B. Chondrodysplasia
C. Dystrophic epidermolysis bullosa
D. Ehlers-Danlos syndrome
E. Osteoarthritis
F. Osteogenesis imperfecta type I
G. Stickler syndrome

A

Osteogenesis imperfecta type I

55
Q

MUTATION: NONSENSE mutations in type II procollagen gene (COL2A1 or COL11A1) reduce number of collagen molecules
SIGNS AND SYMPTOMS: Joint pain, degeneration of vitreous gel and retina

A. Alport syndrome
B. Chondrodysplasia
C. Dystrophic epidermolysis bullosa
D. Ehlers-Danlos syndrome
E. Osteoarthritis
F. Osteogenesis imperfecta type I
G. Stickler syndrome

A

Stickler syndrome

56
Q
  • Caused by different mutations in the same gene resulting to different clinical phenotypes
  • May result from:
  • Mutations in different parts of the gene
  • Mutations that are localized (single base change) or catastrophic (missing gene)
  • Mutations that alter the protein in ways affecting its interaction with other proteins
  • Mutations that affect a protein used in different tissues
A

Allelic Diseases

57
Q

Degree to which a mutation alters a phenotype depending where it occurs in the gene, and how it affects the folding, conformation, activity, or abundance of the protein

A

Importance of Positioning

58
Q

Factors that Lessen the Effects of Mutation
o Mutation in the 3rd position in a codon
= SILENT mutation
o Mutation in the 2nd position in a codon
= REPLACE another amino acid that has a similar structure

a. Genetic code
b. Conditional mutation
c. Stem cells

A

Genetic code

59
Q

Factors that Lessen the Effects of Mutation
o Only affects the phenotype under CERTAIN CONDITIONS: exposures that trigger the symptoms

a. Genetic code
b. Conditional mutation
c. Stem cells

A

Conditional mutation

60
Q

Factors that Lessen the Effects of Mutation
- Therapeutic approaches
a. Genetic code
b. Conditional mutation
c. Stem cells

A

Stem cells

61
Q
  • Change in the basic structure of DNA
  • Cell’s response:
    a. Apoptosis
    b. DNA Repair
    c. Cancer
A

DNA Damage

62
Q
  • Collection of cellular processes aimed to
    detect and correct DNA damage
  • DNA replication is very accurate
    = accomplishment because DNA replicates approx. 10 ^ 16 times during an average human lifetime
  • most mutation occur in somatic cells
A

DNA Repair

63
Q

oversee the accuracy of replication

A

DNA polymerase & DNA damage response genes

64
Q

proofreads the activity during DNA replication

A

DNA polymerase

65
Q

complex network of cellular processes and signaling pathways activated in response to DNA DAMAGE

RAD51: repairs double strand breaks

A

DNA damage response genes

66
Q

Types of DNA Repair
- Cut and paste mechanisms
- Corrects damaged DNA base
- Replaces 1-5 nucleotides at a time
- DNA glycosylase: recognizes a specific base
▪ First to cut the glycosidic bond
▪ Creates an apyrimidinic or apurinic site
- AP endonuclease: recognizes a sugar with the missing base
▪ Makes a cut in the phosphodiester backbone
▪ Removes the deoxyribose sugar
▪ Gap is filled by DNA polymerase and DNA ligase

A. Photoreactivation Repair
B. Excision repair: Base Excision Repair
C. Excision repair: Nucleotide excision repair
D. Mismatch repair
E. Double-stranded break repair

A

Base excision repair

67
Q

Types of DNA Repair
* Targets DNA lesions caused by exposure
to UV light
* Found in fungi, bacteria, archaea, plants,
and some vertebrates
* Photolyases: enzymes that absorb
energy from the visible light and use it to
detect and bind pyrimidine dimers to
break the extra bonds

A. Photoreactivation Repair
B. Base excision repair
C. Excision repair: Nucleotide excision repair
D. Mismatch repair
E. Double-stranded break repair

A

Photoreactivation Repair (light-dependent)

68
Q

Types of DNA Repair
- Repair bulky DNA lesions that alter the
double helix
- Replaces up to 30 nucleotides

A. Photoreactivation Repair
B. Base excision repair
C. Excision repair: Nucleotide excision repair
D. Mismatch repair
E. Double-stranded break repair

A

Nucleotide excision repair

69
Q

Types of DNA Repair
* Excise mismatched base and replace it
with the correct base
* Often occur in microsatellites

A. Photoreactivation Repair
B. Base excision repair
C. Excision repair: Nucleotide excision repair
D. Mismatch repair
E. Double-stranded break repair

A

Mismatch repair

70
Q

Types of DNA Repair
* Heal a broken sugar-phosphate
backbone in both DNA strands as two
types of multiprotein complexes reseal
the backbone structure
* Result from exposure to ionizing
radiation or oxidative damage

A. Photoreactivation Repair
B. Base excision repair
C. Excision repair: Nucleotide excision repair
D. Mismatch repair
E. Double-stranded break repair

A

Double-stranded break repair

71
Q
  • INCORRECT DNA base is placed, but replication and transcription proceed
  • DNA polymerase read past the error
A

Damage tolerance

72
Q
  • Heterozygotes who have one mutant repair gene may be more sensitive to damage from environmental factors, such as TOXINS and RADIATION
  • CHROMOSOME BREAKAGE PERSISTS
  • Cancer develop as errors in the DNA sequence accumulate & are perpetuated to a much greater extent
A

DNA Repair Disorders

73
Q

DNA Repair Disorders
- Caused by at least 5 genes
- Genes affected: ERCC2, ERCC3, GTF2H5, MPLKIP, RNF113A
- Faulty repair: NER, BER, or both
- Symptoms: dwarfism, intellectual
disability, failure to develop, brittle hair, scaly skin
Hearing & vision may fail

a. Trichothiodystrophy
b. Hereditary nonpolyposis colon cancer (Lynch syndrome)
c. Xeroderma pigmentosum
d. Ataxia telangiectasia

A

Trichothiodystrophy

74
Q

DNA Repair Disorders
- DNA repair defect in MICROSATELLITES (all the same length)
o Faulty repair: MMR
o Effects: increased risk of developing
colorectal cancer and other cancer

a. Trichothiodystrophy
b. Hereditary nonpolyposis colon cancer (Lynch syndrome)
c. Xeroderma pigmentosum
d. Ataxia telangiectasia

A

Hereditary nonpolyposis colon cancer (HNPCC) (Lynch syndrome)

75
Q

DNA Repair Disorders
o Rare recessive genetic disorder that results to EXTREME SENSITIVITY TO UV
- deficient “sloppy” DNA polymerase
o Faulty repair: NER or damage tolerance
▪ Allows thymine dimers to stay and block replication
o Symptoms: skin cancers, severe skin abnormalities, developmental and neurological defects

a. Trichothiodystrophy
b. Hereditary nonpolyposis colon cancer (Lynch syndrome)
c. Xeroderma pigmentosum
d. Ataxia telangiectasia

A

Xeroderma pigmentosum

76
Q

DNA Repair Disorders
o Genes affected: ATM, defect in KINASE
▪ Kinase: cell cycle checkpoint
▪ Cells proceed through cell cycle without pausing after replication for inspection and repair
o Faulty repair: DSBR
o Characterization: have 50 times increased risk of developing leukemia
o Symptoms: Poor balance and coordination (ataxia), telangiectasia (red marks on the face), delayed sexual maturation, high risk of
infection and diabetes mellitus

a. Trichothiodystrophy
b. Hereditary nonpolyposis colon cancer (Lynch syndrome)
c. Xeroderma pigmentosum
d. Ataxia telangiectasia

A

Ataxia telangiectasia

CYTOGEN FINALS (11 decks)

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