11 Genetic Basis of Disease
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Transcript of 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$le multi%enic *isor*ers.
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Types o+ geneti& 'isor'ers
1. in%le %ene *isor*ers.2. romosomal *isor*ers.
3. om$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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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* %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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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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Se)(ine'
Gene Inheritan&e
:en %ene is
localie* on ; or Ycromosome.
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Types o+ geneti& 'isor'ers
1. in%le %ene *isor*ers.2. romosomal *isor*ers.
3. om$le multi%enic *isor*ers.
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C"%OMOSOMA DISO%DE%S
Alteration in num,er
(increase or *ecrease)
/r structural can%es
6itin cromosome
6aryotype
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T%ISOM74in&rease' n1m0er5
8resence of an
a**itional (3
r*
)cromosome in an
oter6ise *i$loi*
cromosome
com$le.
#otal no. of
cromosomes is 4=
DO2N8S S7ND%OME
4trisomy 9:, monogo*ism5
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Do-n syn'rome46aryotype5
normal abnormal
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Monosomy4re'1&tion in n1m0er5
45 cromosomes (only
one ; cromosome)
At a*olescence '/
o&ulation menstruation
ort stunte* sterile.
:e,-nec+
Ovarian Dysgenesis
4T1rner;s Syn'rome5
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T1rner8s Syn'rome4aryotype5
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A0norma*ities o+ &hromosome
str1&t1re.
"n many tumors te affecte* cells a&e
constant cromosomal a,normality
IN C"%ONIC M7EOID E!6AEMIA
- translocation ,et6een cromosome
9 an* 22 lea*in% to formation small
cromosome 22 calle*
Philadelphia, or Ph,chromosome.
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"'>!"/'.
More a0norma*ities o+ str1&t1re
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Types o+ geneti& 'isor'ers
1. in%le %ene *isor*ers.2. romosomal *isor*ers.
3. om$le multi%enic *isor*ers.
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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