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Clinical Foundations > Medical Genetics > Flashcards

Medical Genetics Flashcards

1
Q

genotype

A

genetic makeup

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2
Q

phenotype

A

individual’s obeservable traits

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3
Q

allele

A

variant form of gene that exists at same relative locations on homologous chromosomes

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4
Q

homozygous

A

individual inherits the same alleles for particular gene from both paretns

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5
Q

homozygous dominant

A

carries 2 copies of same dominant gene

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6
Q

homozygous recessive

A

carries 2 copies of same recessive gene

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7
Q

heterozygous

A

2 copies of different alleles of a particular gene

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8
Q

hemizygous

A

genetic variant on gene which there is only 1 copy

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9
Q

types of genetic diseases

A

single gene disorders
mitochondrial diseases
chromosomal abnormalities
multifactorial disorders

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10
Q

law of dominance

A

alleles can be dominant or recessive

rather than both alleles contributing to the phenotype the domnant one wll be expressed exclusvely

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11
Q

law of segregation

A

paired genes must segregate equally into gametes such as the offsprings have equal likelihood of inherting either factor

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12
Q

law of independent assortment

A

genes do not nfluence each other with regard to the sorting of alleles into gametes and every possible combo of alleles for every gene is equally likely to occur

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13
Q

recurrence risk

A

probability of producing a child with the genetic disease

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14
Q

autosomal dominant characteristics

A

usual recurrence risk - 50%
transmssion pattern - vertical. ds pheno seen generation to generaton
sex ratio- equal number of males and females usually
other- father to son ratio transmission of disease gene is possible

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15
Q

autosomal recessive characteristics

A

usual recurrence risk- 25%
transmission pattern disease pheno may be seen in multiple siblings, but usually not in earlier generations
sex ratio- usually equal number
other- consanguity s sometmes seen, especally for rare recessive diseases

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16
Q

consanguinity

A

relationship between blood relatives who have at least one common ancestor no more than a great great grandparent

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17
Q

consanguinity consequences

A

increased incidence of congenital malformation, AR disorder and other hearing loss and mental retardation

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18
Q

coefficient of relationship

A

proportion of shared genes, risk of disease increases as proportion increases

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19
Q

incomplete dominance

A

the phenotype of heterozygotes is somewhere in between the pheno of homozygous recessive and homozygous dominant

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20
Q

codominance

A

two alleles are simultaneously expressed and equally contribute to the phenotype

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21
Q

multiple alleles

A

there are 3 or more alternative allelic forms of a gene, only 2 of which can exist in any normal diploid ind

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22
Q

polygenic ingeritance

A

caused by the combined effect of mutations in multiple genes

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23
Q

linked genes

A

genes that are physcally close to one another on the same chromosome and likely to be ingerited together

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24
Q

pleiotropy

A

genes that exet effects on multiple aspects of physiology or anatomy

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25
Q

epistasis

A

effects of one gene are modified by one or several other genes

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26
Q

nonmendelian modes of inheritance

A 
incomplete dominance
codominance
multiple alleles
polygenic ingeritance
linked genes
pleiotropy
epistasis
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27
Q

Sex linked disorders

A

Do not follow models laws of inheritance
X linked dom and rec
Y linked - rare

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28
Q

Xlinked dominant

Recurrence risk for heterozygous femal and normal male

A

50% sons affected

50% daughters affected

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29
Q

X linked dominant

Recurrence risk for affected male and normal female

A

0% of sons

100% daughters

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30
Q

X linked dominant

Transmission pattern

A

Vertical phenotype seen in generation after generation

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31
Q

X linked dominant

Sex ratio

A

Twice as many affected females as affected males

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32
Q

X linked dominate

Other info

A

Male to male transmission is not seen

Expression is less severe in female heterozygous than in affected males

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33
Q

Examples of x linked dominant

A

Hypophosphatemic rickets

Rett syndrome

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34
Q

X linked recessive

Recurrence risk for heterozygous female and normal male

A

50&+% sons affected

50% of daughters heterozygous carriers

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35
Q

Recurrence risk for affected male and normal female

A

0% sons affected

100% daughters heterozygous carriers

36
Q

X linked recessive transmission pattern

A

Skipped generations may be seen, representing transmission through carrier females

37
Q

X linked recessive sex ratio

A

Much greater prevalence of affected males

Affected homozygous females rare

38
Q

X linked recessive

Other

A

Male to male transmission not seen

Manifesting heterozygotes may be seen in females

39
Q

Z linked recessive

Examples

A

Hemophilia A
Duchenne muscular dystrophy
Red green color blindness

40
Q

Y linked. (Holandric) disorders

A

Affects genes only present on Y chromosome
Effected father transmits to son.
Most y chromosomal genes play role in male sexual differentiation, development of sex characteristics. And spermatogenesis

41
Q

Mitochondrial inheritance

A

MtDNA inherited exclusively though maternal line

42
Q

Heteroplasmy

A

Mutated mtDNA variant is found only in portion of ell’s mitochondria

43
Q

Threshold effect

A

Phenotypical expression depends on proportion of cell’s normal mtENA to mutated mtDNA

44
Q

Mitochondrial diseases

A

Kaerns-sayer syndrome
Leber hereditary optic neuropathy LHON
Mitochondrial encephalopathy, lactic acidosis and stroke like episodes (MELAS)
Myoclonic epilepsy and ragged red fiber disease MERRF

45
Q

Imprinting

A

Epigenetic process that differential modifies genes or chromosomal segments in male/female germ line
As result either paternal or maternal allele of gene is active in somatic cells of offspring

46
Q

Imprinting

Genetic mechanisms

A

Chromosomal microdeletions

Uniparental disomy- in which individual inherits two copies of chromosome from one parent and none from the other

47
Q

Prader willi syndrome

A

Chromosome 15 deletion of father

From mother

48
Q

Angelman syndrome

A

Chromosome 15 deletion of mother

From father

49
Q

Anticipation

A

Phenomenon in which the symptoms become more severe or start at an earlier age as a disease is passed on to the next generation

50
Q

Anticipation

Genetic mechanisms

A

Trinucleotide repeats

Number of repeats increase in each following generation

51
Q

Meta centric

A

Shor and long arm similar size

1, 2, 3

52
Q

Submetacentric chromosom

A

Short short arms (chromatids)
Long long arm
Chromosomes 4, 5, x

53
Q

Acrocentric

A

Satellites for short arms, shorter long arms

Chromosome 13 14 15

54
Q

Euploid

A

Appropriate number of chromosomes for their species

55
Q

Polyploid

A

In human incompatible with life

56
Q

Aneuploid

A

Error in chromosome number
Monosomy
Trisomy

57
Q

Numerical chromosomal abnormalities due to

A

No dysfunction

58
Q

Chromosome abnormality

Down syndrome

A

Trisomy 21

59
Q

Chromosome abnormality

Klinefelter syndrome

A

Xxy

60
Q

Chromosome abnormality

Patau syndrome

A

Trisomy 13

61
Q

Chromosome abnormalities

Edwards syndrome

A

Trisomy 18

62
Q

Chromosome abnormality

Turner syndrome

A

Monosomy x

63
Q

Structural chromosomal abnormalities

Balanced

A

Chromosome complement is complete
No loss or gain of genetic material
Generally harmless
At risk of producing children with an unbalanced chromosomal complement

64
Q

Structural abnormalities

Unbalanced

A

Chromosome complement contains incorrect amount of material

Serious clinical consequences

65
Q

Reciprocal translocation

A

Break occurs in each of two chromosomes with the segments being exchanged to form two new derivative chromosomes

66
Q

Robertsonian translocations

A

Particular type of reciprocal translocation in which the breakpoints are located at or close to the centromenres of two acrocentric chromosomes

67
Q

Pericentric inversion

A

Inversion segment involves the centromere

68
Q

Paracentric inversion

A

Inversion segment involves only one arm of the chromosome

69
Q

Ring chromosome

A

Both tips of chromosome can be lost, leaving sticky ends that attach to each other, forming a ring chromosomes

70
Q

Isochromosomes

A

Formed when a chromosome divides along an axis perpendicular to its usual axis of divisions
Produces one chromosome with only the short arms and another with only Long arms

71
Q

Multifactorial/ complex disorders

A

Do not follow a clear inheritance pattern

Symptoms are caused by interplay between several genes and exogenous factors

72
Q

Genetic testing

A

Analysis of chromosomes, dna, rna, or proteins to detect abnormalities that can cause a genetic disease

73
Q

Single gene disorders genetic testing

A 
Detecting variation at DNA or RNA level 
PCR 
Southern blotting
Northern blotting 
Restriction fragment analysis
High throughput DNA sequencing 
Microarray analysis
74
Q

Mitochondrial diseases and multifactorial disorders genetic diseases

A

Detecting dysfunction or variations at protein level
Electrophoresis and western blotting
ELISA
Enzyme activity assays

75
Q

Chromosomal abnormalities genetic diseases

A

Cytogenetic analyses
High resolution banding
FISH
Comparative genomic hybridization

76
Q

Southern blot

Advantages / disadvantages

A

Laborious

Trinucleotide expansions in fragile x.

77
Q

Sizing of PCR productions

Advantages/ disadvantages

A

Simple and cheap

78
Q

ARMS-PCR
Advantages/disadvantages
Examples

A

Simple, cheap

CFTR mutations

79
Q

Oligonucleotide ligation
Advantages/disadvantages
Example

A

Multiplex possible

CFTR mutations

80
Q

Real time PCR
Advantages and disadvantages
Examples

A

Expensive equipment

FVL

81
Q

Sanger sequencing

Advantages/ disadvantages

A

Gold standard
Known or unknown mutations
Any gene

82
Q

Pyrosequencing

Advantages/disadvantages

A

Known or unknown mutations
Any gene
Expensive

83
Q

Next generation sequencing

Advantages/disadvantages

A

Known or unknown mutations
Any gene
Expensive equipmtent, enormous capacity but vast amount of data to analyze
Interpretation of novel variants can be difficult

84
Q

Cytogenetic assay

A

Fish assay

CGH assay

85
Q

Fish assay

A

Labeled probe is hybridized to metaphase, prophase, or interphase chromosomes
Can be used to test for missing or additional chromosomal material as well as chromosome rearrangements
Use of multiple colors to detect several possible alterations simultaneously is possible

86
Q

CGH assay

A

Differential labeled DNA from test and control sources is hybridized to probes in microarrays.
Allows the detection of chromosome duplications and deletions
Can not detect balanced rearrangements

Clinical Foundations (10 decks)

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