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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
epistasis
effects of one gene are modified by one or several other genes
26
nonmendelian modes of inheritance
``` incomplete dominance codominance multiple alleles polygenic ingeritance linked genes pleiotropy epistasis ```
27
Sex linked disorders
Do not follow models laws of inheritance X linked dom and rec Y linked - rare
28
Xlinked dominant | Recurrence risk for heterozygous femal and normal male
50% sons affected | 50% daughters affected
29
X linked dominant | Recurrence risk for affected male and normal female
0% of sons | 100% daughters
30
X linked dominant | Transmission pattern
Vertical phenotype seen in generation after generation
31
X linked dominant | Sex ratio
Twice as many affected females as affected males
32
X linked dominate | Other info
Male to male transmission is not seen | Expression is less severe in female heterozygous than in affected males
33
Examples of x linked dominant
Hypophosphatemic rickets | Rett syndrome
34
X linked recessive | Recurrence risk for heterozygous female and normal male
50&+% sons affected | 50% of daughters heterozygous carriers
35
Recurrence risk for affected male and normal female
0% sons affected | 100% daughters heterozygous carriers
36
X linked recessive transmission pattern
Skipped generations may be seen, representing transmission through carrier females
37
X linked recessive sex ratio
Much greater prevalence of affected males | Affected homozygous females rare
38
X linked recessive | Other
Male to male transmission not seen | Manifesting heterozygotes may be seen in females
39
Z linked recessive | Examples
Hemophilia A Duchenne muscular dystrophy Red green color blindness
40
Y linked. (Holandric) disorders
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
Mitochondrial inheritance
MtDNA inherited exclusively though maternal line
42
Heteroplasmy
Mutated mtDNA variant is found only in portion of ell’s mitochondria
43
Threshold effect
Phenotypical expression depends on proportion of cell’s normal mtENA to mutated mtDNA
44
Mitochondrial diseases
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
Imprinting
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
Imprinting | Genetic mechanisms
Chromosomal microdeletions | Uniparental disomy- in which individual inherits two copies of chromosome from one parent and none from the other
47
Prader willi syndrome
Chromosome 15 deletion of father | From mother
48
Angelman syndrome
Chromosome 15 deletion of mother | From father
49
Anticipation
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
Anticipation | Genetic mechanisms
Trinucleotide repeats | Number of repeats increase in each following generation
51
Meta centric
Shor and long arm similar size | 1, 2, 3
52
Submetacentric chromosom
Short short arms (chromatids) Long long arm Chromosomes 4, 5, x
53
Acrocentric
Satellites for short arms, shorter long arms | Chromosome 13 14 15
54
Euploid
Appropriate number of chromosomes for their species
55
Polyploid
In human incompatible with life
56
Aneuploid
Error in chromosome number Monosomy Trisomy
57
Numerical chromosomal abnormalities due to
No dysfunction
58
Chromosome abnormality | Down syndrome
Trisomy 21
59
Chromosome abnormality | Klinefelter syndrome
Xxy
60
Chromosome abnormality | Patau syndrome
Trisomy 13
61
Chromosome abnormalities | Edwards syndrome
Trisomy 18
62
Chromosome abnormality | Turner syndrome
Monosomy x
63
Structural chromosomal abnormalities | Balanced
Chromosome complement is complete No loss or gain of genetic material Generally harmless At risk of producing children with an unbalanced chromosomal complement
64
Structural abnormalities | Unbalanced
Chromosome complement contains incorrect amount of material | Serious clinical consequences
65
Reciprocal translocation
Break occurs in each of two chromosomes with the segments being exchanged to form two new derivative chromosomes
66
Robertsonian translocations
Particular type of reciprocal translocation in which the breakpoints are located at or close to the centromenres of two acrocentric chromosomes
67
Pericentric inversion
Inversion segment involves the centromere
68
Paracentric inversion
Inversion segment involves only one arm of the chromosome
69
Ring chromosome
Both tips of chromosome can be lost, leaving sticky ends that attach to each other, forming a ring chromosomes
70
Isochromosomes
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
Multifactorial/ complex disorders
Do not follow a clear inheritance pattern | Symptoms are caused by interplay between several genes and exogenous factors
72
Genetic testing
Analysis of chromosomes, dna, rna, or proteins to detect abnormalities that can cause a genetic disease
73
Single gene disorders genetic testing
``` Detecting variation at DNA or RNA level PCR Southern blotting Northern blotting Restriction fragment analysis High throughput DNA sequencing Microarray analysis ```
74
Mitochondrial diseases and multifactorial disorders genetic diseases
Detecting dysfunction or variations at protein level Electrophoresis and western blotting ELISA Enzyme activity assays
75
Chromosomal abnormalities genetic diseases
Cytogenetic analyses High resolution banding FISH Comparative genomic hybridization
76
Southern blot | Advantages / disadvantages
Laborious | Trinucleotide expansions in fragile x.
77
Sizing of PCR productions | Advantages/ disadvantages
Simple and cheap
78
ARMS-PCR Advantages/disadvantages Examples
Simple, cheap | CFTR mutations
79
Oligonucleotide ligation Advantages/disadvantages Example
Multiplex possible | CFTR mutations
80
Real time PCR Advantages and disadvantages Examples
Expensive equipment | FVL
81
Sanger sequencing | Advantages/ disadvantages
Gold standard Known or unknown mutations Any gene
82
Pyrosequencing | Advantages/disadvantages
Known or unknown mutations Any gene Expensive
83
Next generation sequencing | Advantages/disadvantages
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
Cytogenetic assay
Fish assay | CGH assay
85
Fish assay
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
CGH assay
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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