404
T. G. HSU
that all of them may bear satellites (e.g. Ferguson-Smith and Handmaker, 1961), thus making the identification of chromosome pairs
13-15 extremely difficult. Identification of chromosome pairs 21 and 22
by the presence of a satellite is likewise ambiguous after it was found
that satellites may be present on both pairs (Petersen and Therkelsen,
1961). A different interpretation recently expressed by Ohno, Trujillo,
Kaplan and Kinosita (1961) would make the status of these acrocentric
chromosomes more nebulous, for they think satellites may or may not
be present in a given chromosome. When two chromosomes of the
group 21-22 are observed to bear satellites, according to these investigators, they may not be a pair of chromosome 21's, but rather one
member of each of the pairs.
A modification of the Denver system by Patau (1960, 1961), using
group symbols for chromosomes that are not easily identifiable, has
some merits. His method is to classify the chromosomes according to
their lengths and centromeric positions into seven natural categories:
Group A : chromosomes 1,2, and 3
Group B: chromosomes 4 and 5
Group C: chromosomes 6-12 and X
Group D : chromosomes 13, 14 and 15
Group E: chromosomes 16, 17 and 18
Group F: chromosomes 19 and 20
Group G: chromosomes 21, 22 and Y
Actually the Denver Conference classified the human chromosomes
into exactly the same seven groups, but did not suggest group symbols.
In describing a certain chromosome whose identity is not absolutely
established, it is easier to say a chromosome in "Group C " than "Group
X , 6-12". It appears redundant, however, as some investigators prefer,
to use both group symbol and individual number for each chromosome,
such as A3, El7, G22, etc. In this review, when chromosomes are not
identified, the group symbols will be adopted for convenience.
An idiogram of a normal male is shown for the sake of easy reference
in Fig. 3. The female karyotype is omitted because the reader can conveniently delete the Y and add an extra presumed X from the male
picture.
A. THE X X Y GENOTYPE
One of the common sex anomalies in man is the Klinefelter's syndrome. Clinically these patients can be accurately diagnosed only after
puberty. However, after using sex chromatin in somatic nuclei, the
male children with positive sex chromatin should at least be watched
closely because most of the individuals with Klinefelter's syndrome are
T. G. HSU
that all of them may bear satellites (e.g. Ferguson-Smith and Handmaker, 1961), thus making the identification of chromosome pairs
13-15 extremely difficult. Identification of chromosome pairs 21 and 22
by the presence of a satellite is likewise ambiguous after it was found
that satellites may be present on both pairs (Petersen and Therkelsen,
1961). A different interpretation recently expressed by Ohno, Trujillo,
Kaplan and Kinosita (1961) would make the status of these acrocentric
chromosomes more nebulous, for they think satellites may or may not
be present in a given chromosome. When two chromosomes of the
group 21-22 are observed to bear satellites, according to these investigators, they may not be a pair of chromosome 21's, but rather one
member of each of the pairs.
A modification of the Denver system by Patau (1960, 1961), using
group symbols for chromosomes that are not easily identifiable, has
some merits. His method is to classify the chromosomes according to
their lengths and centromeric positions into seven natural categories:
Group A : chromosomes 1,2, and 3
Group B: chromosomes 4 and 5
Group C: chromosomes 6-12 and X
Group D : chromosomes 13, 14 and 15
Group E: chromosomes 16, 17 and 18
Group F: chromosomes 19 and 20
Group G: chromosomes 21, 22 and Y
Actually the Denver Conference classified the human chromosomes
into exactly the same seven groups, but did not suggest group symbols.
In describing a certain chromosome whose identity is not absolutely
established, it is easier to say a chromosome in "Group C " than "Group
X , 6-12". It appears redundant, however, as some investigators prefer,
to use both group symbol and individual number for each chromosome,
such as A3, El7, G22, etc. In this review, when chromosomes are not
identified, the group symbols will be adopted for convenience.
An idiogram of a normal male is shown for the sake of easy reference
in Fig. 3. The female karyotype is omitted because the reader can conveniently delete the Y and add an extra presumed X from the male
picture.
A. THE X X Y GENOTYPE
One of the common sex anomalies in man is the Klinefelter's syndrome. Clinically these patients can be accurately diagnosed only after
puberty. However, after using sex chromatin in somatic nuclei, the
male children with positive sex chromatin should at least be watched
closely because most of the individuals with Klinefelter's syndrome are