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CMMB 413 MT 1 > Clinical Cytogenetics > Flashcards

Clinical Cytogenetics Flashcards

1
Q

Mitochondrial DNA (MtDNA) Properties

A

-circular and lacks introns
-is exclusively maternally inherited
-is 16.5 kb and encodes 37 genes
-mitochondrial-specific transcription and translation

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2
Q

MtDNA Organization

A

-heavy and light strands
-D-loop contains the control region
-replication is variable between cells
-between 1000-10, 000 mtDNA copies within the inner mitochondrial compartment in a cell

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3
Q

7S DNA Strand

A

-causes D-loop in MtDNA due to being triple stranded
-short third strand in MtDNA
-can pair with the the L-strand=displacement of the H-strand + D-loop formation

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4
Q

Maternally Inherited Diabetes and Deafness (MIDD)

A

-1% of diabetic patients and most common in the Japanese population
-mutations in mitochondrial genes, MT-TL1, MT-TK, or MT-TE by reducing tRNA activities

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5
Q

Human Genome Project (HGP)

A

-an international ,collaborative research program aimed to map and understand all the genes (genome) of human beings.
-intron-exon structure distinguishes eukaryotes from prokaryotes.
-introns are spliced out of mRNA before they leave the nucleus
-3.1Gb of DNA (,1.5% encodes proteins, 45% is unique or single-copy, rest is repetitive)

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6
Q

Alpha-satellite

A

-171-bp sequence that can extend to several million base pairs or longer
-near the centromeres of chromosomes

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7
Q

Minisatellites

A

-blocks of tandem repeats (each 11 bplong or greater)
-total length is a few thousand base pairs

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8
Q

Microsatellites

A

-the repeat units are 1-10 bp long
-total length less then a few hundred base pairs

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9
Q

SINE (short interspersed elements) family

A

-10% of the genome (>1 million members)
-member is 300bp in length
ex. Alu family

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10
Q

LINE (long interspersed Nuclear Element or L1) family

A

~20% of the genome (~850,000 members) members could be as long as 6 kb in length

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11
Q

Segmental duplication family

A

->5% of the genome
can span hundreds of kb

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12
Q

Nucleosome

A

the basic repeating structural subunit of the packed chromatin inside the cell’s nucleus
(DNA wrapped around 8 histones)

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13
Q

Solenoid

A

includes 6 nucleosomes
organized into chromatin loops

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14
Q

Ploidy

A

refers to the number of different copies of each chromosome present in a cell
the number of chromatids within a cell is indicated by the letter c

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15
Q

1n 1c

A

one haploid chromosome that is unreplicated

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16
Q

2n 2c

A

two homolog (diploid) unreplicated chromosomes (two chromatids)

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17
Q

1n 2c

A

one single chromosome (haploid) in which DNA has been duplicated

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18
Q

2n 4c

A

two homolog chromosomes (diploid) consisting each of two sister chromatids (two yellow and two blue), thus 4 c in total

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19
Q

Meiosis

A

-is responsible for the production of gametes

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20
Q

genetic consequences of meiosis

A

-shuffling of the genetic materials by recombination
-additional shuffling of genetic material by random assortment of the homologous
-reduction of the chromosome number from diploid (2n) to haploid (n)
-segregation of alleles

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21
Q

Meiotic Nondisjunction

A

the homologous chromosomes or the sister chromatids of a chromosome failed to separate from one another to travel to the opposite poles, resulting in cells that do not have normal number of chromosomes

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22
Q

clinical cytogenetics

A

is the practice of medical genetics by studying the structure and number of chromosomes to identify chromosome abnormalities

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23
Q

Aneuplodiy

A

one or more extra or missing chromosome. instead of 46 chromosomes in a diploid cell

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24
Q

Trisomy

A

extra copy of one chromosome

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25
Triploidy
when you have an entire extra set of chromosomes
26
Tetrasomy
when you have two extra copies of the same chromosome
27
Tetraploidy
when you have two extra sets of chromosomes
28
Chromosomal Abnormalities
-leading cause of pregnancy loss `10-20% ocytes have an extra or missing chromosome -2% of pregnancies in women >35 years
29
autosomal disorder and unbalanced rearrangments
1/230
30
Balanced rearrangements
1/500
31
Indicators- early growth/development
-developmental delay -physical malformations -ambiguous genitalia mental retardation
32
Indicators- Stillbirth
10% stillbirth/neonatal death
33
fertility problems
-amenorrhea -recurrent miscarriage -history of infertility
34
Karotyping
-determine abnormal chromosomal numbers -determine abnormal chromosomal structures caused by rearrangements
35
insertion/deletions
-autosomal deletions occurs at 1/7000 live births
36
translocation
the transfer of a segment of one chromosome to another chromosome
37
Robertsonian translocation
is a translocation between 2 acrocentruc chromosomes by fusion at or near the centromere, with the loss of short arms
38
Routine Karotyping
-cells must be easy to obtain -able to grow rapidly in culture
39
Giemsa banding (G)
-staining with Giemsa stain -light (GC-rich regions) and dark (AT-rich regions) -most common
40
Giemsa stain
nucleic acid, methylene blue, eosin, and Azure B
41
metacentric chromosomes
-more or less central centromere -arms of approximately equal length -1,2,3
42
submetacentric chromosomes
-off-center centromere -arms of different length -4,5
43
acrocentric chromosomes
-centromere near one end -13,14,15, 21,22
44
Quinacrine banding
-staining with quinacrine mustard -detects heteromorphism (homologous pair which are not morphologically identical)
45
Reverse Banding
-Europe -heated before staining -dark and light bands are the revese of the Q and G banding methods -used to analyze distal ends of chromosomes that stain poorly with the other methods
46
C-banding
-method involving Xylene substitute, for staining: -centromeric regions (1q, 9q,16q, distal Yq -regions containing constitutive heterochromatin, and staining darkly at interphase cells
47
Constitutive heterochromatin
hyper-condensed, late replicating, and C-banding positive genomic region, usually consisting of highly repetitive DNA
48
Fluorescence In Situ Hybridization
-uses fluorescent labelled ssDNA probes to hybridize with chromosomes immobilized on microscope slides to identify chromosomal aberrations -gene specific or locus specific probes used to detect chromosomes
49
Spectral Karyotyping
-24 probes of human chromosomes are combined and used for FISH of metaphase chromosomes -each chromosome-specific probe emits it's own signal
49
Spectral Karyotyping
-24 probes of human chromosomes are combined and used for FISH of metaphase chromosomes -each chromosome-specific probe emits it's own signal
50
Plasmid
- an extra-chromosomal DNA molecule found in bacteria and can be replicated independently from the the microoorganism's own chromosomes
51
Vector
-plasmid that is engineered for the applications in molecular biology ex. BAC specially designed
52
Library
collection of clones, which carry vector molecule into which a different fragment of DNA derived from the total DNA or RNA is inserted
53
Genomic DNA
complete or fragment of a gene including introns and exons
54
Genomic library
a collection of total genomic DNA from an organism
55
cDNA
is a coding DNA fragment synthesizexd from a mRNA template using reverse transcription
56
cDNA library
is a combination of caDNA fragments inserted into a collection of host cells, which together constitute the "transcriptome" of the organism
57
Nucleic Acid Hybridization
is a process establishing a sequence-specific interaction between 2 or more complementary strands of nucleic acids into a single complex
58
Comparative Genome Hybridization (CGH)
-used to determine the copy number (or dosage) differences between two distinct DNA samples -useful for detecting deletions and duplications that <1 Mb eg. copy number polymorphism
59
CGH Limitation
when used with metaphase chromosomes deletions/duplications smaller than 5-10 Mb cannot be detected microscopically. enter aCGH
60
DNA Microarray
-collection of microscopic DNA spotted onto a solid surface for measuring the expression levels of large number of genes simultaneously or to genotype multiple regions of a genome
61
Rett Syndrom Microarray
-x-linked dominant affects motor skills and language -loss of function of the MECP2 gene which encodes a nuclear protein that binds methylated DNA and recruits histone deacetylase to methylated DNA; or in over expression as in MECP2 duplication syndrome
62
Genomic Hybridization Techniques
FISH SKY CGH Microarray
63
Whole Genome Sequencing
-alignment of sequence reads from a patient's genome to the reference sequence
64
Clastogens
chromosome breaking agents
65
mosaicism
mutation occurs in one cell of the developing embryo
66
Duplication
can be caused by unequal crossing over between misaligned homologous chromosomes or sister chromatids
67
Haploinsufficiency
the inability if a single copy of a gene to carry out the function normally performed by two copies
68
Pallister-Killian Syndrome
craniofacial, retardation duplication of chromosome 12p
69
Marker Chromosome
-very small chromosome annot be identified -1/2500 -likely to be ring
70
Ring chromosomes
formed by two breaks and the broken ends of the chromosome reunite in ring stucture
71
Isochromosome
chromosome in which one arm is missing (partial monosomy) and the other duplicated (partial trisomy)
72
Mechanisms for isochromosome formation
-mis-division through centromere -defective meiotic crossover
73
pseudodicentric
dicentric chromosomes that are -mitotically table due to one of the two centromeres in inactivated -both centromeres always coordinate their movement to one of the mitotic pole during segregation
74
Dicentric chromosomes
chromosomes that have 2 centromeres
75
Balanced rearrangements
no phenotypic effect for carrier -chromosomal inversions paracentric, pericentric -chromosomal translocations reciprocal, Robertsonian, insertion
76
Chromosomal inversion
occurs when a single chromosome undergoes 2 breaks and is reconstituted with the segment between the break inverted
77
Paracentric inversion
-no centromer -both breaks occur in one arm -arm ratio is not altered -determined with banding or FISH (locus probes)
78
Pericentric incersion
-includes centromere -break in each arm -easier to be identified due to changes in banding patterns
79
Chromosomal translocation
involves the exchange of chromosome segments between 2 non-homologous chromosomes
80
Reciprocal Translocation
-total genetic material remains the same -chromosome number is unchanged
81
Robertsonian translocation
-deletion of short arms (acrocentric chromosomes) -one less chromosome
82
Chromatid
one of the two identical halves of a chromosome that has been replicated in preparation for cell division
83
Chromatin
mixture of DNA and proteins that form the chromosomes found in the cells of humans and other higher organisms

CMMB 413 MT 1 (1 decks)

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