Cytogenetics

Cytogenetics is essentially a branch of genetics, but is also a part of cell biology/cytology (a subdivision of human anatomy), that is concerned with how the chromosomes relate to cell behaviour, particularly to their behaviour during mitosis and meiosis. Techniques used include karyotyping, analysis of G-banded chromosomes, other cytogenetic banding techniques, as well as molecular cytogenetics such as fluorescence in situ hybridization (FISH) and comparative genomic hybridization (CGH). History Beginnings Chromosomes were first observed in plant cells by Carl Nägeli in 1842. Their behavior in animal (salamander) cells was described by Walther Flemming, the discoverer of mitosis, in 1882. The name was coined by another German anatomist, von Waldeyer in 1888. 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 hav

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Genetic characterization of CHO production host DG44 and derivative recombinant cell lines

Martin Bertschinger, Madiha Derouazi, David Hacker, Florian Maria Wurm

The dihydrofolate reductase-deficient Chinese hamster ovary (CHO) cell line DG44 is the dominant mammalian host for recombinant protein manufacturing, in large part because of the availability of a well-characterized genetic selection and amplification system. However, this cell line has not been studied at the cytogenetic level. Here, the first detailed karyotype analysis of DG44 and several recombinant derivative cell lines is described. In contrast to the 22 chromosomes in diploid Chinese hamster cells, DG44 has 20 chromosomes, only seven of which are normal. In addition, four Z group chromosomes, seven derivative chromosomes, and 2 marker chromosomes were identified. For all but one of the 16 DG44-derived recombinant cell lines analyzed, a single integration site was detected by fluorescence in situ hybridization regardless of the gene delivery method (calcium phosphate-DNA coprecipitation or microinjection), the topology of the DNA (circular or linear), or the integrated plasmid copy number (between 1 and 51). Chromosomal aberrations, observed in more than half of the cell lines studied, were mostly unbalanced with examples of aneuploidy, deletions, and complex rearrangements. The results demonstrate that chromosomal aberrations are frequently associated with the establishment of recombinant CHO DG44 cell lines. Noteworthy, there was no direct correlation between the stability of the genome and the stability of recombinant protein expression.

2006

High susceptibility for diploidy in ovulated oocytes from XO mice

Friedrich Beermann

Adult female mice of the "sensitive" NMRI/Han strain ovulate diploid oocytes after gonadotropin treatment. Other mouse strains are "non-sensitive" with respect to the ovulation of such diploid oocytes. In this study we combined the impaired ovarian situation in the XO karyotype with the trait "diploidy", which is determined genetically, by mating Ta/O (Ta = Tabby) females of C3H X 101 background to males of the NMRI/Han strain. The adult female F1 hybrids were stimulated to ovulation by gonadotropins and identified by their karyotype (XX or XO). The cytogenetic analysis of ovulated oocytes revealed a low level of diploidy in the XX littermates (1.0%), but a very high level in females with the XO karyotype (24.6%). All of the XO females ovulated at least one diploid oocyte. We suggest that it is the XO status which drastically impairs meiosis I in our "gonadotropin-sensitive" F1 females due to (1) alterations of the developmental program within the oocyte, (2) a disturbed communication between oocyte and follicle, (3) a preferential maturation and ovulation of "follicles at risk", or (4) an exceptional recruitment of many such follicles, by, e.g., a premature responsiveness to gonadotropins in our XO females. An interdependence of several such mechanisms is possible.

1986

Molecular and cytogenetic analysis of an interstitial 20p deletion associated with syndromic intrahepatic ductular hypoplasia (Alagille syndrome)

Friedrich Beermann

High-resolution chromosome analysis of a 19-year-old female proband with syndromic intrahepatic ductular hypoplasia (Alagille syndrome, AWS) revealed an interstitial deletion of chromosome 20p with breakpoints provisionally located in or close to p11.22 and p12.2. Southern blots from digests of DNA of the proband and her chromosomally normal parents were hybridized with the human DNA probes pR12.21, HuPrPcDNA2, and pDS6-SgI, which have been mapped to the region 20 (p12-pter), and rehybridized with the F IX probe for calibration. Comparing the hybridization signals of the normally sized DNA fragments of the family, we found no evidence for loss of any of the three tested distal chromosome 20p loci in our proband. Furthermore, in situ hybridization with HuPrPcDNA2 revealed a specific accumulation of grains at or around the faint distal G band suspected to represent all or most of band p12.3 of the proband's deleted 20p and at p12 of the normal chromosome 20. Thus the AWS of our proband is associated with an interstitial deletion that preserved the three tested distal loci on 20p. Since nine further reported cases of 20p deletion are clinically similar, we propose AWS as a further "contiguous gene syndrome" and assign it to an approximately 8-Mb-large chromosome 20p segment (provisionally, p11.23-p12.1).

1989

Karyotype

A karyotype is the general appearance of the complete set of chromosomes in the cells of a species or in an individual organism, mainly including their sizes, numbers, and shapes. Karyotyping is the

Chromosome

A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cell

Chromosomal translocation

In genetics, chromosome translocation is a phenomenon that results in unusual rearrangement of chromosomes. This includes balanced and unbalanced translocation, with two main types: reciprocal, and R

BIO-205: Cellular and molecular biology I

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The students are exposed to experimental and analytical approaches specific to single cell biology, with an emphasis on quantitative aspects.