11 genetic basis of disease

8/9/2019 11 Genetic Basis of Disease

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GENES

A geneis a molecular unit of.. H!D"#Y($assin% of trait to offs$rin% from its $arents).

GENEis a name %i&en to some areas / segmentsof D'A tat co*e for a $oly$e$ti*e.


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Genotype v/s Phenotype

#e %enetic ma+eu$ of

in*i&i*ual

#e effects $ro*uce* ,y

tese %enes.


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Some More Terms.....

OC!S ac %ene is situate* at a s$ecific site onone of a $air of cromosomes te %enes

formin% a $air are calle*AEES.

"omo#ygote$ "f te %enes (alleles) are ali+e.

"etero#ygote "f te %enes (alleles) are '/# ali+e.


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MODE OF IN"E%ITANCE

Dominant%enes

$ro*uce effects ,otin eteroy%ote in

omoy%ote

mem,ers.

%e&essive%enes$ro*uce teir

effects only in

omoy%otemem,ers.


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Interme'iate inheritan&e v/s Co(Dominan&e

An e)amp*e +or interme'iate inheritan&e is, the patients

-ith si&*e &e** anemia, in -hi&h the hetero#ygote has

the si&*e(&e** trait 'i++ers 0oth +rom norma* in'ivi'1a*

patient -ith si&*e(&e** anemia


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So, 2hat is a Geneti& 'isor'er3

A %enetic *isor*er is a con*ition

cause* ,y a,normalities in

'or H!///.


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Types o+ geneti& 'isor'ers

1. in%le %ene *isor*ers.2. romosomal *isor*ers.

3. om$le multi%enic *isor*ers.


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Sing*e gene 'isor'ers

1. Autosomal *ominant (AD)

2. Autosomal recessi&e (A!).

3. e-lin+e* %ene lin+e*.


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A1tosoma* Dominant Disease

On*y one &opy of an allele is necessary for

an in*i&i*ual to %et te *isease.

A$$ears in ,ot eteroy%ous

omoy%ous mem,ers.

#e *isease a$$ears in e&ery %eneration.


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A1tosoma* Dominant Disease


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A1tosoma* 'ominant

'iseases 4preva*en&e5

#e tree most common AD *iseases in te6orl*.....

1. 7amilial y$ercolesterolemia (1 in 500)

2. 8olycystic +i*ney *isease (1 in 1250)

3. 'eurofi,romatosis ty$e " (1 in 2500)


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A1tosoma* %e&essive Inheritan&e

A normal or a,normal %enetic trait is

transmitte* from $arent to offs$rin% T2O&opies o+ this gene M!ST ,e $resent in

or*er for te trait to *e&elo$.

#is means tat *isease occurs only in

homo#ygo1smem,ers.


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A1tosoma* re&essive

'iseases 4preva*en&e5

#e tree most common A! *iseases in te

6orl*.....

1. ic+le cell anemia (1 in 25)

2. ystic fi,rosis (1 in 2000)

3. #ay-acs *isease (1 in 3000)


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Si&*e Ce** Anemia


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Se)(ine'

Gene Inheritan&e

:en %ene is

localie* on ; or Ycromosome.


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C"%OMOSOMA DISO%DE%S

Alteration in num,er

(increase or *ecrease)

/r structural can%es

6itin cromosome

6aryotype


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T%ISOM74in&rease' n1m0er5

8resence of an

a**itional (3

r*

)cromosome in an

oter6ise *i$loi*

cromosome

com$le.

#otal no. of

cromosomes is 4=

DO2N8S S7ND%OME

4trisomy 9:, monogo*ism5


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Do-n syn'rome46aryotype5

normal abnormal


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Monosomy4re'1&tion in n1m0er5

45 cromosomes (only

one ; cromosome)

At a*olescence '/

o&ulation menstruation

ort stunte* sterile.

:e,-nec+

Ovarian Dysgenesis

4T1rner;s Syn'rome5


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T1rner8s Syn'rome4aryotype5


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A0norma*ities o+ &hromosome

str1&t1re.

"n many tumors te affecte* cells a&e

constant cromosomal a,normality

IN C"%ONIC M7EOID E!6AEMIA

- translocation ,et6een cromosome

9 an* 22 lea*in% to formation small

cromosome 22 calle*

Philadelphia, or Ph,chromosome.


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"'>!"/'.

More a0norma*ities o+ str1&t1re


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COMPE< M!TIGENIC DISO%DE%S

Disor*er cause* ,y com,ination of

small &ariation in %enes 6it in&ol&ement ofen&ironmental factors lifestyle (also calle*

multifactorial *iseases).

1. Heart *iseases.

2. Dia,etes.


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GENETIC TESTING

:. Bio&hemi&a* geneti& testing - assay for

s$ecific meta,olites tat in*icate a %enetic

*isease (alactosemia #ay acs Disease).

9. Dire&t geneti& testing - eamination of D'A to

*etermine if mutations are $resent. (ic+le cell anemia ,eta telassemia).

3. Cytogeneti& testing? (Do6n@s syn*rome).


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Do-n syn'rome46aryotype5

normal abnormal


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3. Cytogenetic testing - Deletions

11 genetic basis of disease

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