Female cell

Uncultured cells have also been used to a limited extent for fetal sex determination. This Is possible because the cells can be appropriately stained and examined for the presence of sex chromatin, characteristic of female cells, and for the fluorescent Y-body, characteristic of male cells (33,34). However, these cytologic techniques are not completely reliable, and It Is still desirable to determine fetal sex by direct chromosome analysis (35). 

A number of bacterial viruses have RNA genomes. The best-known bacterial RNA viruses have single-stranded RNA. Interestingly, the bacterial RNA viruses known in the enteric bacteria group infect only bacterial cells which behave as gene donors (males) in genetic recombination. This restriction to male bacterial cells arises because these viruses infect bacteria by attaching to male-specific pili. Since such pili are absent on female cells, these RNA viruses are unable to attach to the females, and hence do not initiate infection in females. 

Bacteriophage T7 Bacteriophage T7 and its close relative T3 are relatively small DNA viruses that infect Escherichia coli. (Some strains of Shigella and Pasteurella are also hosts for phage T7.) The virus particle has an icosahedral head and a very small tail. The virus particle is fairly complex, with S different proteins in the head and 3-6 different proteins in the tail. One tail protein, the tail fiber protein, is the means by which the virus particle attaches to the bacterial cell surface. Only female cells of Escherichia coli can be infected with T7 male cells can be infected but the multiplication process is terminated during the latent period. 

In addition to the 22 pairs, a female cell contains two X chromosomes and a male cell contains an X and a Y chromosome. When a female egg (carrying an X chromosome) combines with male sperm having an X chromosome, a female offspring is born. When the egg combines with a sperm having a Y chromosome, a male offspring results. 

When an Hfr strain conjugates with an F (female), replication of the entire male chromosome commences at some point near the end of the integrated F agent, and genes of the bacterial chromosome followed by those of the F factor are transferred into the female. Only a single strand of DNA (customarily referred to as the plus strand) is transferred from the donor cell and into the recipient cell (Fig. 26-3). There the complementary minus strand is synthesized to form a complete double-stranded DNA molecule bearing the genes from the Hfr cell. Only rarely does a copy of the entire chromosome of the donor cell enter the female cell. More often the DNA strand, or perhaps the pilus itself, breaks and only part of the chromosome is transferred. 

The X chromosomes. The phenomenon of X chromosome inactivation in mammalian female cells is closely related to imprinting, which has been discussed in Section 1. The inactivation process is quite complex. It involves methylation of 5 -CpG-3 sequences of DNA, as is described in Chapter 27, Section B,6. It also depends upon an inactivation center, the Xist gene, which is expressed only from the inactivated Xj chromosome, whose Xist DNA is unmethylated. On the Xa chromosome this DNA is methylated, and the gene is silent.272 The Xist transcript is a long RNA that may bind to and coat much of the XL... 

Geller, A. and Muller, D. G., Analysis of the flagellar beat pattern of male Ectocarpus siliculosus gametes (Phaeophyta) in relation to chemotactic stimulation by female cells, J. Exp. Biol., 92,53, 1981. 

Gametes are haploid reproductive male or female cells. Gametes with opposite sex fuse with each other, forming a zygote. 

X chromosome and one Y chromosome, which has different genes than the X chromosome. Yet the genes on the X chromosome must, for the most part, be equally active in female cells (XX) and male cells (XY). To achieve this balance, one of the X chromosomes in female cells is chemically modified and condensed into a very small mass called a Barr body, which is inactive and never transcribed. 

For possible mutational studies with these loci, it would be technically difficult to detect a reverse mutation accompanied by a loss of metachromasia. On the other hand, by using normal male or female cells, any forward recessive mutations either in one X chromosome or one autosome may be detectable if the expression of metachromasia is unequivocal. However, it may be that metachromasia is not as specific a cellular phenotype as was originally hoped (Nadler et aLy 1969 Taysi et al.y 1969 Milunsky and... 

Priest, J. H., Heady, J. E., and Priest, R. E. (1967), Synchronization of human diploid cells by fluorodeoxyridine. The first ten minutes of synthesis in female cells, J. Nat, Cancer Inst, 38, 61-72. 

Zygotic embiyogenesis is a key process in flowering plants, and it is a well coordinated series of developmental events governed from the very beginning by cell polarity and asymmetric cell division in which male and female cells participate. 

PCR for the ZJy gene detects the presence of a Y chromosome. However, it should be noted that an EG cell line that is negative for this PCR product may actually be an XO cell line, not a normal XX female cell line. It would be necessary to perform karyotype analysis to determine the difference between an XO and an XX cell line accurately. 

F Cell A cell lacking the F plasmid called recipient or female cell. 

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