Reproduction, sexual

Sexual reproduction Sexually transmitted diseases Sharks Sheep... 

Saliva can also be important in mammalian reproduction. Sexually aroused boar produce from the submaxillary gland a copious, sticky saliva containing 3-a-hydroxy-5a-androst-16-ene and 5-a-androst-16-ene-3-one (70, 71) which act as sexual pheromones for the male 49, 307, 308). 

Yeasts belonging to Basidior cetes form external spores. ia.yiscomjcetes sexual reproduction occurs with the formation of spores in a cell that serves as a spore sac or ascus. Generally four, but sometimes eight or more, spores are formed in each ascus. This is sometimes reflected in the species name, ie,... 

Figure 11.11 shows examples of the three basic genetic operations of reproduction, crossover and mutation, as applied to a population of 8-bit chromosomes. Reproduction makes a set of identical copies of a given chromosome, where the number of copies depends on the chromosome s fitness (see below). The crossover operator exchanges subparts of two chromosomes, where the position of the crossover is randomly selected, and is thus a crude facsimile of biological sexual recombination between two single-chromosome organisms. The mutation operator randomly flips one or more bits in the chromosome, where the bit positions are randomly chosen. 

Reproductive Toxicity—The occurrence of adverse effects on the reproductive system that may result from exposure to a chemical. The toxicity may be directed to the reproductive organs and/or the related endocrine system. The manifestation of such toxicity may be noted as alterations in sexual behavior, fertility, pregnancy outcomes, or modifications in other functions that are dependent on the integrity of this system. 

Gray LE, Ostby J, Wolf C, et al. 1998. The value of mechanistic studies in laboratory animals for the prediction of reproductive effects in wildlife Endocrine effects of mammalian sexual differentiation. Environ Toxicol Chem 17(1) 109-118. 

Jobling, S., Beresford, N., and Nolan, M. (2002b). Altered sexual maturation and gamete production in wild roach (Rutilus rutilus) living in rivers that receive treated sewage effluents. Biology of Reproduction 66, 272-281. 

Milnes, M.R., Bryan, T.A., and Katsu, Y. et al. (2008). Increased post hatching mortality and loss of sexually dimorphic gene expression in alligators Alligator mississippiensis) from a contaminated environment. Biology of Reproduction 1 07.064915. 

F-pili or sex strands are partofa primitive genetic exchange system in some bacterial species. Part of the genetic material may be passed from one cell to another through the hollow pilus, thus giving rise to a simple form of sexual reproduction. 

For many years, it was thought that binary fission was the only method of reproduction in bacteria, but it is now known that there are three methods of reproduction in which genetic exchange can occur between pairs of cells, and thus a form of sexual reproduction is exhibited. These processes are transformation, conjugation and transduction. Further details ofthese processes as they affect antibiotic resistance will be found in Chapter 9. 

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