Practical 3 Flashcards
(18 cards)
There are — chromosomes in each nucleus of the human cells
46
Only — cells ( — & — ) have half no.chromosomes
Sex , sperm , egg
Karyotyping is used to —— chromosomes for any structural / numerical abnormalities
Analyse
What is karyotyping ? In which ——
Cytogenetic technique
chromosomes are prepared from a cell culture, then imaged under the microscope
Karyotyping is done in the —— stage of mitosis, why ?
Metaphase
because metaphase chromosomes appear shortest & thickest , so they are more obvious under microscope
What are types of cells used for karyotyping ?
1- rapidly dividing/can be stimulated to divide in cell culture
2- peripheral blood { WBCs / lymphocytes are usually used }
3- bone marrow
4- amniotic fluid
Why are RBCs not used for karyotyping?
Because they don’t have nucleus
Why is Colchicine added to culture?
To stop cell division at metaphase stage
Cells are fixed with ?
Methanol / acetic acid
Why is trypsin used to treat cell ?
It partially digests some of the chromosomal proteins. Allowing dye to access DNA
Slides are stained in —— stain
giemsa
Chromosomes are visualised under light microscope at —X
40
Sequence the steps for karyotyping
1- draw 5 ml venous blood
2- add phytoheam agglute & culture medium
3- culture at 37ْC for 3 days
4- add colchicine & hypotonic saline
5- cells fixed
6- spread cells onto slide by dropping
7- Digest with trypsin & stain with giemsa
8- analyse metaphase spread
9- karyotype
How do we write a karyotype notation?
Total no.chromosomes , sex chromosomes , + extra chromosome
If extra sex chromosome remove this part ( + extra chromosome ) and add it to sex chromosomes
If missing chromosomes X0
Write a karyotype notation of a male with Down syndrome
47 , XY , + 21
Write a karyotype notation of male with Klinefelter syndrome
47 , XXY
Write a karyotype notation of normal female
46 , XX
Write a karyotype notation of female with Edward’s syndrome
47 , XX , +18
