2 - MUTATIONS

Question 1

• Heritable changes in the nucleotide sequence of a given DNA
• Substitution, deletion or insertion of one or more nucleotides
• Could affect or not a given phenotype
• The major basis of diversity among organisms
• The raw material of evolution

Answer 1

Mutations

Question 2

Caused (mostly) by

Answer 2

mutagens

Question 3

UV radiation, ionizing radiation (e.g., gamma rays, X-rays), byproducts (e.g., reactive oxygen species such as superoxides, hydroxyl radicals)

Answer 3

DNA damage

Question 4

(e.g., base analogs: 5-bromouracil (5-BU), 2-amino-purine; alkylating
agents: ethylmethane sulfonate (EMS); intercalating agents: proflavine, acridine orange, ethidium bromide)

Answer 4

mutagens

Question 5

(e.g., base excision repair, nucleotide excision repair, mismatch-repair system)

Answer 5

Can be repaired by the body in normal conditions

Question 6

Classifications of Mutations

Answer 6

Based on nature of occurrence
Based on cell type where it occurs

Question 7

Based on nature of occurrence

Answer 7

Spontaneous
Induced

Question 8

arise in the absence of known mutagen

Answer 8

Spontaneous

Question 9

presence of mutagens or environmental agents

Answer 9

Induced

Question 10

Based on cell type where it occurs

Answer 10

Somatic
Gametic

Question 11

originates in mitosis and affects subset of cells

Answer 11

Somatic

Question 12

originates in meiosis and affects all cells of an individual

Answer 12

Gametic

Question 13

Gametic

Answer 13

Autosomal
X-linked

Question 14

change in the sense of information (missense)

Answer 14

Substitution

Question 15

purine to purine or pyrimidine to pyrimidine

Answer 15

Transition

Question 16

purine to pyrimidine or vice versa

Answer 16

Transversion

Question 17

deletion or insertion of one base

Answer 17

Frameshift

Question 18

change of one letter

Answer 18

point mutation

Question 19

loss of one letter

Answer 19

deletion (frameshift mutation)

Question 20

gain of one letter

Answer 20

insertion (frameshift mutation)

Question 21

mutation changes 1 codon for an amino acid into another codon for that same amino acid

Answer 21

Silent

Question 22

codon for 1 amino acid is replaced by a codon for another amino acid

Answer 22

Missense

Question 23

• codon specifies chemically similar amino acid
• Does not alter protein function in many cases

Answer 23

Synonymous missense

Question 24

codon specifies chemically dissimilar amino acid

Answer 24

Nonsynonymous missense

Question 25

Phenylalanine

Answer 25

non-polar, hydrophobic

Question 26

Serine

Answer 26

polar, hydrophilic

Question 27

Point mutations and multiple variants in the “a determinant" region can destroy the ? of HBV

Answer 27

antigenicity and immunogenicity

Question 28

codon for 1 amino acid is replaced by a translation termination codon

Answer 28

Nonsense

Question 29

A region from one chromosome is aberrantly attached to another chromosome

Answer 29

Translocation

Question 30

examples of translocation

Answer 30

Burkitts Lymphoma Chronic Myelogenous Leukemia (bcr-abl gene)

Question 31

* 20% of all leukemia cases * characterized by an overproduction of cells of granulocytic and occasionally monocytic series * presence of Philadelphia chromosome in >90% of patients

Answer 31

Chronic Myelogenous Leukemia

Question 32

* short-term lymphocyte culture * lymphocyte harvest * slide preparation and staining * slide analysis

Answer 32

routine chromosomal analysis

Question 33

* standard media composed of RPMI 1640, fetal bovine serum and penicillin-streptomycin * addition of phytohemagglutinin --> induces mitotic activity * 72-hour culture

Answer 33

short-term lymphocyte culture

Question 34

* addition of colcemid --> prevents formation of spindle fibers * centrifugation * hypotonic solution --> disrupts cytoplasmic material in cells * fixation

Answer 34

lymphocyte harvest

Question 35

* 24-hour slide aging * GTG-banding technique (G-bands by Trypsin using Giemsa)

Answer 35

slide preparation and staining

Question 36

* based on International System of Human Cytogenetic Nomenclature (ISCN) * chromosomes are arranged according to size and banding pattern * Cytovision by Applied Imaging Inc * Ikaros by Metasystems Inc

Answer 36

slide analysis

Question 37

* numerical abnormalities --> deviation from the normal chromosome number (46) * structural abnormalities --> change in structure and morphology

Answer 37

slide analysis

Question 38

* treat metaphase spread with trypsin that digests part of chromosomal protein. * Stain with Giemsa and observe under light microscope.

Answer 38

Giemsa G-banding

Question 39

fluorescent staining method which uses quinacrine to identify chromosomes and their structural anomalies

Answer 39

Quinacrine Q-banding

Question 40

involves denaturing in hot acidic saline followed by Giemsa staining

Answer 40

Reverse R-banding

Question 41

used in identifying heterochromatin by denaturing chromosomes in a saturated alkaline solution followed by Giemsa staining

Answer 41

Centromere C-banding

Question 42

Numerical chromosome abnormalities

Answer 42

* Trisomy 21 (47, + 21) * Trisomy 18 (47, + 18) * Trisomy 13 (47, + 13)

Question 43

Sex chromosome abnormalities

Answer 43

* Turner syndrome (45, X) * Klinefelter syndrome (47, XXY)

Question 44

Structural chromosome abnormalities

Answer 44

* Deletion * Duplication * Translocation * Inversion

Question 45

Trisomy 21

Answer 45

Down Syndrome (47, + 21)

Question 46

Trisomy 18

Answer 46

Edward Syndrome (47, + 18)

Question 47

Trisomy 13

Answer 47

Patau Syndrome (47,+ 13)

Question 48

* A laboratory technique for detecting and locating a specific DNA sequence on a chromosome. * The technique relies on exposing chromosomes to a small DNA sequence called a probe that has a fluorescent molecule attached to it. * The probe sequence binds to its corresponding sequence on the chromosome. * Useful in disorders with very small aberrations or samples with no metaphase cells available.

Answer 48

Fluorescence in situ hybridization (FISH)

Question 49

Steps in FISH

Answer 49

* Denaturation of the sample * Hybridization of probe to target cells * Washing * Detection (fluorescent microscopy)

Question 50

Detection of BCR-ABL (Breakpoint Cluster Region-Abelson) gene fusion by FISH using

Answer 50

bone marrow aspirate or peripheral blood

Question 51

Detection of AML-ETO (Acute Myeloid Leukemia) gene fusion by FISH using

Answer 51

bone marrow aspirate or peripheral blood

Question 52

Detection of PML-RAR (ProMyelocytic Leukemia-Retinoic Acid Receptor) gene fusion by FISH using

Answer 52

bone marrow aspirate

Question 53

Detection of Y-Chromosome for sex-mismatched bone marrow transplantation by FISH using

Answer 53

bone marrow aspirate

Question 54

BCR-ABL

Answer 54

Breakpoint Cluster Region-Abelson

Question 55

AML-ETO

Answer 55

Acute Myeloid Leukemia

Question 56

PML-RAR

Answer 56

ProMyelocytic Leukemia-Retinoic Acid Receptor