Yes, the best studies of XYY males indicate that they are more prone to aggressive behavior than XY males. No, the presence of the extra Y chromosome in XYY males does not in and of itself produce aggressive behavior in those affected; dealing with aspects of the condition during adolescence is a more likely explanation for any later social difficulties experienced by XYY males.
Human karyotype[ edit ] human karyotype male The normal human karyotypes contain 22 pairs of autosomal chromosomes and one pair of sex chromosomes allosomes. Any variation from the standard karyotype may lead to developmental abnormalities.
Diversity and evolution of karyotypes[ edit ] Although the replication and transcription of DNA is highly standardized in eukaryotesthe same cannot be said for their karyotypes, which are highly variable.
There is variation between species in chromosome number, and in detailed organization, despite their construction from the same macromolecules. This variation provides the basis for a range of studies in evolutionary cytology.
In some cases there is even significant variation within species. In a review, Godfrey and Masters conclude: In our view, it is unlikely that one process or the other can independently account for the wide range of karyotype structures that are observed But, used in conjunction with other phylogenetic data, karyotypic fissioning may help to explain dramatic differences in diploid numbers between closely related species, which were previously inexplicable.
We have a very poor understanding of the causes of karyotype evolution, despite many careful investigations In some species, as in many sciarid fliesentire chromosomes are eliminated during development. In this process, found in some copepods and roundworms such as Ascaris suumportions of the chromosomes are cast away in particular cells.
This process is a carefully organised genome rearrangement where new telomeres are constructed and certain heterochromatin regions are lost. The inactivation of one X chromosome takes place during the early development of mammals see Barr body and dosage compensation.
In placental mammalsthe inactivation is random as between the two Xs; thus the mammalian female is a mosaic in respect of her X chromosomes. In marsupials it is always the paternal X which is inactivated. The diploid number of the Chinese muntjac, Muntiacus reevesiwas found to be 46, all telocentric.
They kept quiet for two or three years because they thought something was wrong with their tissue culture But when they obtained a couple more specimens they confirmed [their findings]. Fundamental number[ edit ] The fundamental number, FN, of a karyotype is the number of visible major chromosomal arms per set of chromosomes.
The fundamental autosomal number or autosomal fundamental number, FNa  or AN,  of a karyotype is the number of visible major chromosomal arms per set of autosomes non- sex-linked chromosomes. Ploidy[ edit ] Ploidy is the number of complete sets of chromosomes in a cell. Polyploidywhere there are more than two sets of homologous chromosomes in the cells, occurs mainly in plants.
It has been of major significance in plant evolution according to Stebbins. Polyploidy in animals is much less common, but it has been significant in some groups. Haplo-diploidywhere one sex is diploidand the other haploid. It is a common arrangement in the Hymenopteraand in some other groups.
Endopolyploidy occurs when in adult differentiated tissues the cells have ceased to divide by mitosisbut the nuclei contain more than the original somatic number of chromosomes.
The cells do not always contain exact multiples powers of twowhich is why the simple definition 'an increase in the number of chromosome sets caused by replication without cell division' is not quite accurate.
This process especially studied in insects and some higher plants such as maize may be a developmental strategy for increasing the productivity of tissues which are highly active in biosynthesis. Aneuploidy[ edit ] Aneuploidy is the condition in which the chromosome number in the cells is not the typical number for the species.Klinefelter syndrome is a condition that occurs in men as a result of an extra X chromosome.
The most common symptom is infertility.
Humans have 46 chromosomes, which contain all of a person's genes and DNA. Two of these chromosomes, the sex chromosomes, determine a person?s gender. Both of the sex. The androgen insensitivity syndrome is an X-linked recessive disorder in which affected males have female external genitalia, female breast development, blind vagina, absent uterus and female adnexa, and abdominal or inguinal testes, despite a normal male 46,XY karyotype.
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TDF was ultimately mapped to the human Y chromosome by molecular examination of sex-reversed patients. Analysis of 4 XX males with testes who had minute portions of the Y material translocated to the X chromosome was critical in defining the sex-determining region on the human Y chromosome (Palmer et al., ; Sinclair et al., ).The sex-determining region on the human Y chromosome .
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