PENGANTAR KROMOSOM

7/26/2019 PENGANTAR KROMOSOM

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HUMAN CHROMOSOMES& GENETIC COUNSELLING

Dr. Minawati, MMed



CHROMOSOME INTRODUCTION

CHROMOSOME

• CENTRAL DOGMA

• NOMENCLATURE/CLASSIFICATION

BANDINGTECHNIQUES

• Q, G, R, C, NEOBINDING

• FISH• COMPARATIVE

GENOMICHYBRIDIZATION

CHROMOSOMALABERRATIONS

• POLYPLOIDY• ANEUPLOIDY:

MONOSOMY,TRISOMY

• DELETION, INSERTION,INVERSION,

TRANSLOCATIONS,ETC.



What is Chromosome?



THE CELL CYCLE



MITOSIS



CHROMOSOME:

STRUCTURE & MORPHOLOGY



CHROMOSOME:




GENE EXPRESSION



CHROMOSOMES BANDING



ISCN (International System for Cytogenetic Nomenclature)

Chromosome 1 Chromosome 12



P = petite

Q = queued

Waldeyer

(1888)metaphase

chromosome



Chromosometranslocations:dangerousliaisonsrevisited

Janet D.Rowley

NatureReviewsCancer 1,245-250(December2001)

http://www.nature.com/nrc/journal/v1/n3/full/nrc1201-245a.html












‘fish’ or ‘FISH’ ?



FISH



Flow Cytometry



Spectral karyotyping &multicolor-FISH



Comparative Genomic Hybridization



CHROMOSOMAL ABERRATIONS



General Guidelines:

modal number, sex chrom, abn

abbrev (first chrom; second chrom)

(arm band number; arm bandnumber)

Ex:

46,XX,t(1;2)(p32;q22)



Symbols and Abbreviations:

, Separates chromosomemodal number, sexchromosomes, and

chromosome abnormalities

- Loss of a chromosome

( ) Surround structurallyaltered chromosomes and

breakpoints

+ Gain of a chromosome

; Separates rearrangedchromosomes and breakpoints

involving more than onechromosome

/ Separates cell lines orclones

// Separates recipient anddonor cell lines in bone

marrow transplants

h Heterochromaticregion of chromosome




del Deletion

dup Duplication of a portionof a chromosome

ins Insertion of a portion ofa chromosome

der

dic Dicentric chromosome

Fra Fragile site (usually usedwith Fragile-X syndrome)

i Isochromosome (both armsof the chromosome are the

same)




inv Inversion

q Long armof a chromosome

r Ringchromosome

tri Trisomy

p Short armof a chromosome

psu dic Only one

centromere is active(pseudo dicentric)

t Translocation

ter Terminal endof arm (i.e. 2qter -end of the long armof chromosome 2)



NUMERICAL ABERATIONS



TRANSLOCATION



TRANSLOCATION

Philadelphia

Chromosome



DELETION

Chromosome

18 Deletions



CRI DU CHAT Chromosome

-



INVERSION & RING CHROMOSOME

-



RING CHROMOSOME

Arq. Neuro-

Psiquiatr. vol.60

no.3A São

Paulo Sept. 2002

EPILEPSY AND

RING

CHROMOSOME

20



INVERSION



Pericentric inversion of chromosome 9

Positivereproductivefamily historyfor spontaneousabortion:predictor forrecurrent

miscarriage inyoung couples

European Journalof Obstetrics &Gynecology andReproductiveBiology

Volume 161,Issue 2, April2012, Pages182 – 186

http://www.sciencedirect.com/science/journal/03012115





http://www.sciencedirect.com/science/journal/03012115/161/2











DICENTRIC CHROMOSOME



CHROMOSOME 18 ABERRATIONS

Life with a

Chromosome

18 Condition

http://www.ch

romosome18.org/WhoWeAr

e/LifewithaCh

romosome18C

ondition/tabid

/782/Default.

aspx




Another

condition:

Pitt-Hopkin

Syndrome



GENETIC COUNSELLING

“If we have another child, what is

the likelihood that our next child will

have Trisomy 18?”

“If we have another child, what isthe likelihood that our next child willhave Down Syndrome?”



GENETIC COUNSELLING

-



DOWN SYNDROME

1% if nondisjunction or maternal age-adjusted riskif that is greater (this represents an increased riskfor patients under age 30 and we're unsure why)

recurrence risk for familial 14/21 translocationvaries according to which parent is affected bybalanced Robertsonian translocation (3-5% males10-15% females)

100% if parent has 21/21 translocation (rare) no increased risk if child has a de novo

translocation



GENETIC COUNSELLING

Genetic

Counselling

for

Chromosomall

Aberration:

Robertsonian

Translocation



GENETIC COUNSELLING

Genetic

Counselling

for

Chromosom

Aberration:

Down

Syndrome



GENETIC COUNSELLING

NON

DISJUNCTION

N N N



GENETIC COUNSELLING

Genetic

Counselling

for other

chromosom

aberrations:

Inversion

&

Ring

chromosome



PEDIGREE



TAKE HOME MESSAGES



TAKE HOME MESSAGES

REFERRENCES



REFERRENCES

http://www.nature.com/scitable/topicpage/cytogenetic-methods-and-disease-flow-cytometry-cgh-772

http://cpd.screening.nhs.uk/timeline

http://www.chromosome18.org/LinkClick.aspx?fileticket=hfLGlJST6

mk%3d&tabid=127 http://www.geneticseducation.nhs.uk/media/33917/family%20hist

ory%20part%201.pdf


http://www.nature.com/scitable/topicpage/chromosome-abnormalities-and-cancer-cytogenetics-879

http://www.authorstream.com/Presentation/chhabra61-439811-chromosome-banding-techniques/
















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