two copies of chromosomes are in a human karyotype.
two copies of chromosomes are in a human karyotype.
how many chromosomes are in a human karyotype?
two copies
the next stage took place after the development of genetics in the early 20th century, when it was appreciated that the set of chromosomes (the karyotype) was the carrier of the genes. levitsky seems to have been the first to define the karyotype as the phenotypic appearance of the somatic chromosomes, in contrast to their genic contents. investigation into the human karyotype took many years to settle the most basic question: how many chromosomes does a normal diploid human cell contain? in 1912, hans von winiwarter reported 47 chromosomes in spermatogonia and 48 in oogonia, concluding an xx/xo sex determination mechanism. painter in 1922 was not certain whether the diploid number of humans was 46 or 48, at first favoring 46. he revised his opinion later from 46 to 48, and he correctly insisted on humans having an xx/xy system of sex-determination. considering their techniques, these results were quite remarkable. in science books, the number of human chromosomes remained at 48 for over thirty years. new techniques were needed to correct this error. joe hin tjio working in albert levan's lab was responsible for finding the approach:
cytogenetics
a full account of a karyotype may therefore include the number, type, shape and banding of the chromosomes, as well as other cytogenetic information.









































variation is often found:









































bullet::::1. between the sexes,









































bullet::::2. between the germ-line and soma (between gametes and the rest of the body),









































bullet::::3. between members of a population (chromosome polymorphism),









































bullet::::4. in geographic specialization, and









































bullet::::5. in mosaics or otherwise abnormal individuals.









































section::::observations on karyotypes.:human karyotype.
karyotype