ALEXANDRIAFACULTY

OF Medicine

•Chromosomes are classified according to length into 7major groups :A,B,C,D,E,F&G

Group A Chromosomes 1: 3

Chromosomes 1 & 2 have similar lengths, but…

Chromosmes 1& 3 are METACENTRIC ,but….

Group B

Chromosomes 4 & 5.

Chromosomes 4 & 5 are very similar!

They are large & sub-metacentric.

GROUP C Chromosomes 6:12 &(XX) or only one X. middle-sized & Metacentric or Sub-metacentric. Female 16 C Chrom. Male 15 C Chrom.

or

Group D Chromosomes 13:15.

middle-sized & Acrocentric.

They have Satellites.

Easy to be distinguished!

Group E Chromosomes 16:18.

Smaller than chrom. D

P-arm of chrom. 17 &18 is shorter than chrom. 16.

16 Metacentric . 17&18 sub-metacentric

Group F Chromosomes 19&20.

They are Metacentric.

Chromosomes 19 and 20 can’t be distinguished!

Group G Chromosomes 21,22 & Y.

Chrom. 21&22 are the smallest pair.

They have Satellites.

Chrom. Y is longer than 21&22.

Y does not have Satellites.

• Chromosomes painting using different probes.So, designing of a probe is very important !

1

• Useful in defining rearrangements &marker chromosomes in clinical & cancer cytogenetics.

2

del 1q t(4;11) t(5;9)

Summary

Classification of chromosomes according to length>>>

7 groups (A,B,C,D,E,F &G).

Spectral karyotyping >>>> leukemia