Kar Yo Typing

7/17/2019 Kar Yo Typing

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What Is a Chromosome?A long, continuous strand of DNA, plus several

types of associated proteins, and RNA.


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Cytogenetics: the study of chromosomes, theirstructure, and their inheritance.

The importance of chromosomes in medicine: Clinical diagnosis Eg, Turner syndrome

Gene mapping Eg, cystic fibrosis

Cancer cytogenetics Eg, retinoblastoma

Prenatal diagnosis Eg, Don syndrome


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Stal!

p

"#

#$

ACR%C&N'RIC(&'AC&N'RIC S)*(&'AC&N'RIC

Stal

CentromereSatellite

!+ongArm

!-

Short

Arm

p-p

p

!

"#

Size:

! chromosome " is largest, chromosome ## smallest

Centromere position:

! metacentric, submetacentric, acrocentric

! all chromosomes ha$e a shorter arm, p, and a longer arm, q.

Karyotype: a picture of all the chromosomes arranged by type:Karyotype also refers to the standard chromosome set of an individual or a species.


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G-banding:

pattern subdi$ides

each chromosome

arm into regions.


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". Cells %from blood, amniotic fluid, or chorionic $illus& are gron in culture.

'itogens may be re(uired: lymphocytes re(uire phytohemagglutinin

#. Colcemid stops cells at metaphase.

). *ypotonic shoc+ ruptures -Cs, sells lymphocytes.

. Cells are fi/ed in 'e0*1*02c.

3. Chromosomes are spread on a slide.

4. Trypsini5ation and staining ith Giemsa re$eals G6bands.

7. The chromosome spread is photographed and arranged by type.

Karyotypes are made from metaphase chromosomes:


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8deogram of G6banding

pattern at 396band

stage:

*igh6resolution bandings of 339639 bands can

be made from prometaphase chromosomes.


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8ntroduction of molecular

cytogenetics: D;2 in chromosome spreads is denatured and

hybridi5ed to probes:


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=>?: chromosome6specific probes

Normal karyotype Cancer cell karyotype

note: translocations, polysomy, monosomy


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Cells used for +aryotyping: -lood cells:

T6lymphocytes from peripheral blood are easily collected Groth in culture re(uires mitogens %phytohemagglutinin&

Cultures are short6li$ed

=+in cells


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8ndications for chromosome analysis:

non chromosomal abnormality of first6degree relati$e

Pre$ious child ith chromosomal aberration

ecurrence ris+ "6# 2d$anced maternal age: F)3 years

'other carries 6lin+ed disorder

'ale offspring ould be at ris+


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Prenatal testing:

Chorion

*ladder

Catheter

)terus

Developing

placenta

Rectum

Amniotic

cavity

Chorionic

villi)ltrasound to monitor

procedure

Developing fetus

Amniocentesis: Chorionic villus sampling:


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0ther reasons for chromosome analysis:


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>elainan >romosom Pada 2bortus

=pontan


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>elainan >romosom Pada -ayi -aru

Hahir

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