Cri-du-chat Syndrome

In response to Qs by Hamudy via chat box:

...The syndrome above is definitely not found anywhere mentioned in our Biology Syllabus...and...The Question will never ask your anything abt its symptom, its prevention or its treatment..Never...never...never...
But when it involves the human karyotype...YES..you must be able to identify the karyotype of NORMAL human ...

Karyotype - A picture of a person's chromosomes, arranged by size and grouped into homologous pairs

Occasionally, errors occur during cell division that result in the offspring receiving too many or too few chromosomes (euploidy)

Polyploidy - three or more complete sets of chromosomes. common in plants
Aneuploidy - when an organism has more or less than the normal (monosomy / trisomy)
example: Down's Syndrome ( Trisomy #21)

Other Syndromes - Turner (XO), Klinefelter (XXY), Edward (Trisomy 13), Supermale (XYY), Poly-X Females (XXX)

Williams Syndrome - deletion on chromosome 7
Cri du Chat Syndrome - deletion on chromosome 5

........then only you can compare the different in karyotype of those who are having these few syndromes....including Down's Syndrome, Cri-du-chat Syndrome....please name a few more....syndromes which occurs DUE TO CHROMOSOMAL MUTATION...

You will notice that the question asked is within the syllabus requirement. Lets have a look at the Qs carefully:

Question (SBP Trial 2007)

Diagram shows the karyotype of a normal person and a person with Cri-du- Chat syndrome


karyotype of a normal person

i) Determine the sex of person with above karyotype.[1m]

ii) Based on the Diagram , explain why Cri-du-chat syndrome occur ? [2m]

Suggested Answer:

Able to determine the sex
answer:
female

Able to state the cause and explain the cause of Cri-du-Chat Syndrome
Sample answer:
1. Chromosome mutation
2. a portion of chromosome number 5 was deleted// break off


Well...When you look at the sample answer..it is indeed within the syllabus.

1. You must know the Diagram of the karyotypes..You have to compare the normal and locate what is missing in the diseased one!!(The Qs will give you the diagram of the normal one so that you can compare)

2. The cause : It could be gene mutation? chromosomal mutation? or sex-linked?

If it involves the changes in the structure of chromosome, then it is CHROMOSOMAL MUTATION!!!

Explain the cause:

Deletion (A) ? Translocation (C) ? Duplication (D) ? Inversion (B) ?

...Which chromosome number?

..So now,you can just be familiar with some of the Karyotypes such as Turner's syndrome,

Klinefelter's syndrome,...be it male or female...depending on their sex-chromosome

The karyotype of NORMAL, MALE human

Karyotype of FEMALE, DOWN'S SYNDROME

...So dont worry...the question will revolve around the WHO? WHAT?WHY?WHEN?..and HOW?