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[MT 6315] Cytogen > Unit 5: Chromosomal Aberrations > Flashcards

Unit 5: Chromosomal Aberrations Flashcards

1
Q

organization of chromosomes

A

linear DNA > looped around by histone protein > chromatin > (condensation) chromosome

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2
Q

defined by DNA

A

gene

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3
Q

refers to the arms of chromosomes

A

chromatids

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4
Q

chromosome in metaphase

A

2 sets of DNA / tetraploid (4n)

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5
Q

dark band and tightly packed by H1 in between 2 nucleosome

A

heterochromatin

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6
Q

why 2 versions of bands?

A

transcription factor cannot access heterochromatin so H1 needs to relax the structure para maaccess ang transcription factors

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7
Q

causes nucleosomes to tightly pack together. transcription factors cannot bind the DNA and genes are not expressed

A

methylation of DNA & histones (heterochromatin)

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7
Q

results in loose packing of nucleosomes. transcription factors can bind the DNA and genes are expressed

A

histone acetylation (euchromatin)

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8
Q

light band and loose

A

euchromatin

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9
Q

regions with high transcriptional activity are loosely packed

A

acetylation

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9
Q

regions with low or no transcriptional activity are densely packed

A

methylation

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10
Q

locus of the gene parts

A

located chromosome
arm
band
sub band
sub sub band

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10
Q

how are bands numbered?

A

numbered from the centromere going outward

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11
Q

made of hexameric repeats and protects the chromosomes

A

telomere

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12
Q
  • These are variations from the wild-type condition in either chromosome structure or chromosome number.
  • These arise spontaneously or induced by chemical or radiation mutagens.
A

chromosomal mutations

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13
Q

variation = ______; level of the chromosome = _________

A

mutation; aberration

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14
Q

an alteration of the nucleotide sequence of a gene

A

gene mutation

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15
Q

where does the alteration occur in gene mutation?

A

nucleotide sequence of a gene

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16
Q

caused by errors in DNA replication and mutagens such as UV and chemicals

A

gene mutation

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17
Q

any substance that can cause mutation

A

mutagens

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18
Q

a single gene is affected

A

gene mutation

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19
Q

influence is comparatively low

A

gene mutation

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20
Q

can cause sickle cell anemia, hemophilia, cystic fibrosis, huntington syncrome, tay-sachs disease and cancers

A

gene mutation

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20
Q

caused by errors in crossing over during meiosis

A

chromosomal mutations

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21
Q

alterations in the chromosome structure and number

A

chromosomal mutations

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22
Q

where does the alteration occur in chromosomal mutations?

A

in a segment of a chromosome

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22
Q

several genes are affected

A

chromosomal mutations

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22
Q

can cause klinefelter syndrome, turner syndrome, down syndrome

A

chromosomal mutations

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23
Q

can sometimes be lethal

A

chromosomal mutations

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24
Q

main difference between gene and chromosomal mutation

A

chromosomal mutation = may phenotypic expression
gene muta = wala

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25
Q

most common chromosome abnormality in spontaneous abortions

A

Trisomics (39k)

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25
Q

most common gender in sex chromosome aneuploids

A

males (1427)

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26
Q

Variation in Chromosome Structure

A
  • Deletion
  • Duplication
  • Inversion
  • Translocation
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27
Q

Variation in Chromosome Number

A
  • Aneuploidy (Monosomics/Trisomics/Nullisomics/Tetrasomics)
  • Polyploidy
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28
Q

the presence of an abnormal number of chromosomes

A

aneuploidy

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29
Q

loss of a single chromosome copy

A

monosomic

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29
Q

unbalanced set of chromosomes = relative gene dosage is upset (example: trisomy of chromosome 21)

A

aneuploid

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29
Q

the presence of more than 2 homologous chromosome sets

A

polyploidy

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30
Q

extra copies of single chromosomes

A

polysomic

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31
Q

T/F: Most chromosome abnormalities are lethal, frequently in spontaneous abortions

A

T

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31
Q

exceptions in spontaneous abortions

A

trisomy 13
trisomy 18
trisomy 21
sex chromosomes

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32
Q

An extra X or Y chromosome usually has a relatively mild effect. Why?

A

1) X chromosome inactivation/Dosage Compensation
2) Not much (essential) on the Y

EXAMPLES:
* Trisomy-X = 47, XXX (female)
* Double-Y = 47, XYY (male)
* Klinefelter Syndrome = 47, XXY (male,
sterile)
* Turner Syndrome = 45, X (female, sterile)

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33
Q

An extra or missing chromosome

A

aneuploidy

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33
Q

Extra chromosome sets

A

polyploidy

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34
Q

One chromosome absent

A

monosomy

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35
Q

One chromosome extra

A

trisomy

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35
Q

Part of a chromosome missing

A

deletion

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36
Q

Part of a chromosome present twice

A

duplication

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37
Q

Two chromosomes join long arms or exchange parts

A

translocation

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38
Q

Segment of chromosome reversed

A

inversion

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38
Q

A chromosome with identical arms

A

isochromosome

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38
Q

A chromosome that forms a ring due to deletions in telomeres, which cause ends to adhere

A

ring chromosome

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39
Q

nawala yung telomere kaya nagfuse

A

ring chromosome

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39
Q

what variation in chromosome structure is chronic myelogenous leukemia (9 & 22)?

A

translocation

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40
Q

two different chromosomes have exchanged segments with each other

A

reciprocal translocation

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41
Q

an entire chromosome attaches to another at the centromere

A

robertsonian translocation

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42
Q

the inverted segment includes the centromere (with both arms involved)

A

pericentric inversion

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43
Q

the two breaks appear on the same side of the centromere (in the same arm)

A

paracentric inversion

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44
Q

It involves the loss of a segment of a chromosome.

A

deletions

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44
Q

starts in breaks of chromosomes. These breaks maybe caused by agents (such as heat, ionizing radiation, viruses, transposable elements) or by errors in recombination.

A

deletion

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45
Q

where is the deleted segment located?

A

anywhere along the chromosome

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45
Q

If dominant dominant ‘A’ is lost in a deletion, then recessive ‘a’ will express itself. This expression of a recessive trait is called _________

A

Pseudodominance

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45
Q

T/F: If the missing genes are of physiological importance, the organism will not survive

A

T

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46
Q

an international standard for human
chromosome nomenclature, which includes band names, symbols and abbreviated terms used in the description of human chromosome and chromosome abnormalities.

A

International System for Human Cytogenomic Nomenclature (ISCN)

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46
Q

abbreviation for deletions of parts of a chromosome

A

del

47
Q

symbol for chromosome deletions

A

-

48
Q

a deletion that occurs towards the end of a chromosome

A

terminal deletion

48
Q

T/F: Micro-deletion is usually found in adults with physical abnormalities. A large amount of deletion would result in immediate abortion (miscarriage)

A

F; usually found in children

48
Q

a deletion that occurs from the interior of a chromosome

A

Intercalary/interstitial deletion

48
Q

a relatively small amount of deletion (up to 5Mb that could include a dozen genes)

A

microdeletion

49
Q

cri du chat syndrome deletion

A

5p-

49
Q

retinoblastoma deletion

A

13q

49
Q

prader-willi syndrome deletion

A

15q-

50
Q

wilms tumor deletion

A

11q-

51
Q

Kidney tumors, genital and urinary tract abnormalities

A

Wilms tumor

51
Q

Cancer of the eye, increased risk of other cancers

A

Retinoblastoma

51
Q

Infants: weak slow growth; children and adults: obesity, compulsive eating

Affected infants have poor sucking reflex. By age 5-6, children become compulsive eaters. Other symtoms include poor sexual development in males, behavioral
problems and mental retardation

A

Prader-Willi syndrome

51
Q

Infants have catlike cry, some facial anomalies, severe mental retardation

Mentally retarded, with defects on facial
development, gastrointestinal malformations, and abnormal throat structures.

A

Cri du chat syndrome

52
Q

Deletions in the long arm of chromosome 15 between bands of q11 and q13.

A

Prader-Willi syndrome

53
Q

s a genetic disorder. It causes delayed development, problems with speech and balance, intellectual disability, and sometimes, seizures.

A

angelman syndrome

54
Q

T/F: People with Angelman syndrome often smile and laugh frequently, and have happy, excitable personalities.

A

T

55
Q

first signs of angelman syndrome (months)

A

developmental delays which begin between about 6 & 12 months of age

56
Q

at what age do children with angelman syndrome experience seizure?

A

2-3 yo

57
Q

is located on the segment of chromosome 15 that is often deleted in people with this disorder.

A

OCA2 gene

58
Q

In some people who have Angelman syndrome, the loss of a gene called _____ is associated with light-colored hair and fair skin

A

OCA2

59
Q

It is a chromosomal mutation that results in the doubling of a segment of a chromosome.

A

duplication

60
Q

the duplicated sections are adjacent to the original

A

tandem duplication

61
Q

Forms of Chromosome Duplication

A

Tandem
Reverse Tandem
Terminal Tandem

61
Q

the presence of extrachromosomal segment causing duplication of a set of genes on the same arm, but in reverse order, in the same chromosome.

A

reverse tandem

62
Q

tandem duplication at the end of a chromosome

A

terminal tandem duplication

63
Q

T/F: The duplications are deleterious.

A

F; not deleterious

64
Q

T/F: The duplication is useful in evolution of new genetic material position such as reallocation of chromosomal material
without altering its quantity may result in an altered phenotype. Example: Position Effect in Drosophila

A

T

65
Q

It is a chromosomal mutation that results when a segment of a chromosome is excised and then reintegrated in an orientation 180O from the original orientation.

A

Inversion

66
Q

abbreviation for inversions

A

inv

67
Q

chromosomes twist into a loop in the
region in which the gene order is inverted

A

Inversion heterozygote

68
Q

T/F: Inversions do not alter the genetic content but change the linear sequence of genetic information

A

T

69
Q
  • Does not include centromere
  • Crossing-over produces one acentric (no centromere) and one dicentric (two
    centromeres) chromosome
A

paracentric inversion

70
Q

what does paracentric inversion produce when crossing over?

A

1 acentric
1 dicentric

71
Q
  • Includes centromere
  • Crossing-over results in duplications and
    deletions of genetic information
A

Pericentric inversion

72
Q

The ______ chromatids fail to move to either pole due to lack of centromere. The _______ chromatids have two centromeres and are connected by a bridge, breaks and contains duplications and deficiencies.

A

acentric; dicentric

73
Q

T/F: When crossing over occurs within the inverted segment of a pericentric inversion, then acentric and dicentric chromatids are formed.

A

F; paracentric

74
Q

change in position of a chromosome segment within the same chromosome.

A

intrachromosomal

74
Q
  • There is a change in position of chromosome segments and the gene
    sequences they contain.
  • no gain or loss of genetic material
A

translocation

74
Q

transfer of a chromosome segment from one chromosome into a nonhomologous chromosome.

A

interchromosomal

74
Q

The broken piece gets attached to one end of the chromosomes.

A

simple translocation

75
Q

The broken segment segment of one chromosome gets inserted interstitially in a chromosome.

A

shift translocation

76
Q

A segment from one chromosome is exchanged with a segment from another non homologous one, so that in reality two translocation chromosomes are simultaneously achieved.
* Homozygotic and heterozygotic translocation

A

reciprocal translocation

77
Q

T/F: Homozygotes do not have any cytological peculiarities and undergo regular pairing during meiosis and cannot be detected cytologically.

A

T

77
Q

T/F: In translocation of heterozygotes, breaks occur on only one of the chromosomes of a homologous pair. In heterozygotic translocation a considerable degree of meiotic irregularities occur.

A

T

78
Q

exchange of segments between two chromosomes

A

reciprocal interchromosomal translocation

78
Q

used to denote a translocation between chromosome A and chromosome B

A

t(A;B)(p1;q2)

78
Q

transfer of segment in one direction from one chromosome to another

A

non-reciprocal interchromosomal translocation

79
Q

the short arms and/or the long arms of
the same chromosome join at the centromere

A

isochromes

79
Q

creates two copies of a large genetic
region

A

isochromes

79
Q

show characteristic mirror image appearance of banding patterns extending in both directions from centromere

A

isochromes

79
Q
  • special cases of joining at centromeres
  • occur between chromosomes that have tiny short arms (acrocentrics)
  • no obvious lost in genetic information because the short arms contain repeated rRNA genes
  • forms a very recognizable and long product
A

robertsonian translocation

80
Q

It involves reciprocal translocation between the long arm of chromosome 22 and chromosome 9.

A

chronic myelogenous leukemia

81
Q
  • Transition of c-abl within the bcr
  • It results to uncontrolled replication of myeloblasts
A

chronic myelogenous leukemia

81
Q

Leukemic cells have ________ __________

A

Philadelphia chromosome

82
Q
  • Common disease in Africa
  • Virus-induced tumor; malignant B cells secrete antibodies
A

burkitt’s lymphoma

82
Q

T/F: Chromosome mutations may occur which results in variation in the number of individual chromosomes or in variation in complete sets of chromosomes.

A

T

82
Q

Organism or cell has one or exact multiple of complete set(s) of chromosomes

A

euploidy

83
Q

⦿ It involves reciprocal translocation between chromosome 8 and 14.
⦿ Activation of c-myc

A

burkitt’s lymphoma

84
Q

One or several chromosomes are lost from or added to the normal set of chromosomes.

A

aneuploidy

84
Q

aneuploidy results from?

A

nondisjunction

85
Q

irregular distribution of sister chromatids during mitosis or of homologous chromosomes during meiosis

A

nondisjunction

86
Q

Phenotypic effects range from minor physical symptoms to devastating and lethal deficiencies in major organ systems.

A

aneuploidy

86
Q

involves a loss of one homologous pair; 2N-2

A

nullisomy

86
Q

involves a loss of a single chromosome; 2N-1

A

monosomy

86
Q

involves a single extra chromosome; 2N+1

A

trisomy

87
Q

Phenotypic features – wide skull that is flat at the back; eyelids have an epicanthic fold; iris contains spots; tongue are furrowed & protruding; physical growth, behavior and mental development are retarded; some have congenital heart defects.

A

Down Syndrome / Trisomy 21

87
Q

*It occurs when there are three copies of chromosome 21.
*Condition named as mongolism (but not used anymore)

A

Down Syndrome / Trisomy 21

87
Q

involves an extra chromosome pair; 2N+2

A

tetrasomy

87
Q

Phenotypic features – cleft lip and palate; small eyes; polydactyly (extra fingers and toes); mental and developmental retardation; severe malformations of the brain and nervous system

A

Patau Syndrome / Trisomy 13

88
Q
  • Three copies of chromosome 13
  • Most affected infants die before the age of three months.
A

Patau Syndrome / Trisomy 13

89
Q
  • Most affected infants are female.
  • Average survival time is 2-4 months
A

Edward Syndrome / Trisomy 18

90
Q

why is maternal age the leading risk factor for autosomal trisomy?

A
  1. The integrity of primary oocytes decreases as the woman age.
  2. Maternal selection becomes less effective.
90
Q

T/F: Maternal age is the leading risk factor for autosomal trisomy

A

T

90
Q

Phenotypic features – have multiple congenital malformations affecting almost every organ system; clenched fists; elongated skull; low-set malformed ears; mental and developmental retardation.

A

Edward Syndrome / Trisomy 18

91
Q
  • Monosomy for the X chromosome
  • Complete absence of X chromosome in the absence or presence of Y chromosome is always lethal.
A

Turner Syndrome (45 X)

91
Q

Phenotypic features do not develop until puberty.

A

Klinefelter Syndrome (47 XXY)

91
Q

Phenotypic features – short and wide chested; extra folds of skin on the neck, underdeveloped breasts and rudimentary ovaries, absence of Barr body, color blindness, narrowing of aorta

A

Turner Syndrome (45 X)

92
Q

Phenotypic features – poor sexual development; very low fertility; with breast development

A

Klinefelter Syndrome (47 XXY)

92
Q
  • Phenotypic features – above average height, suffered personality disorders, below normal intelligence
  • Early studies associate violent criminal behavior with the presence of extra Y chromosome.
A

XYY Syndrome (47 XYY)

93
Q

T/F: X chromosome is essential for survival.

A

T

93
Q

involves variations from the normal state in the number of complete sets of chromosomes.

A

Polyploidy

93
Q

Abnormalities in the number of haploid
chromosomal sets can arise in several ways

A
  • Errors in meiosis during gamete formation
  • Events in fertilization
  • Errors in mitosis following fertilization
94
Q

The basic chromosome set, from which all the other genomes are formed, is called the _____ ____

A

monoploid set

95
Q

Through the formation of unreduced gametes that have double the normal complement of chromosomes or through abortive mitotic division, called _________

A

endoreduplication

95
Q

T/F: Polyploids can arise from genome duplications occurring before or after fertilization

A

T

96
Q

T/F: Polyploid species have multiple complete sets of chromosomes

A

T

97
Q

most common form of polyploidy

A

triploidy

98
Q

Forms of triploidy

A

69 XXY
69 XXX
69 XYY

99
Q

T/F: triploid infants have only limited survival, and most die within a month.

A

T

100
Q

A male with a translocation between the short arm of chromosome 7 at band 21.1
and the long arm of chromosome 9 at band 34.1

A

46, XY t (7;9) (p21.1; q34.1)

100
Q

Indicates the number, the chromosome
sex chromosome constitution, and the nature of the specific abnormality

A

chromosomal shorthand

101
Q

A male missing part of the long arm of chromosome 7

A

46, XY del (7q)

102
Q

A female with trisomy 21 Down Syndrome

A

47, XX, +21

103
Q

Triplo-X syndrome (female)

A

47, XXX

103
Q

A male or female with Trisomy 13 or Patau Syndrome

A

47, XY +13 or 47, XX +13

103
Q

A male or female with Trisomy 18 or Edward Syndrome

A

47, XY +18 or 47, XX +18

[MT 6315] Cytogen (9 decks)

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