E 92 e 93 b 94 asexual reproduction produces

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91. E 92. E 93. B 94. Asexual reproduction produces offspring that are genetically identical to the parent and to each other. Advantages of asexual reproduction are avoidance of risks associated with mating, and efficient use of resources. A disadvantage of asexual reproduction is lack of genetic diversity. Means of asexual reproduction include budding, regeneration, and parthenogenesis. Asexually reproducing organisms tend to be sessile and therefore cannot search for mates, or species that live in sparse populations and rarely encounter potential mates. Sexual reproduction consists of three basic steps: gametogenesis, mating, and fertilization. Genetic diversity is created by the recombination of genes during gametogenesis and by the independent assortment of chromosomes. Mating and fertilization also contribute to genetic diversity. In animals, sexual reproduction encompasses the fusion of two distinct gametes to form a zygote. Gametes are produced by a type of cell division called meiosis. The gametes are haploid (containing only one set of chromosomes) while the zygote is diploid (containing two sets of chromosomes). In most cases, the male gamete, called the spermatozoon, is relatively motile and usually has flagella. On the other hand, the female gamete, called the ovum, is nonmotile and relatively large in comparison to the male gamete. There are two mechanisms by which fertilization can take place. The first is external (the eggs are fertilized outside of the body); the second is internal (the eggs are fertilized within the female reproductive tract). A disadvantage of sexual reproduction is that it is not a continuous activity. It is subject to certain patterns and cycles. Oftentimes these patterns and cycles may be linked to environmental conditions which allow organisms to reproduce effectively. For example, many animals have estrous cycles that occur during certain parts of the year so that offspring can typically be born under favorable conditions. Likewise, these cycles and patterns can be controlled by hormonal cues as well as other seasonal cues like rainfall. These cycles and patterns allow organisms to manage the relative expenditure of energy for reproduction and maximize the chances of survival for the resulting offspring. 95. a./b.) The polymerase chain reaction is a way to make multiple copies of a fragment of DNA. A starting template is needed, along with primers, free nucletodies, and DNA ligase. The steps of the PCR reaction are denaturation, annealing, and elongation. The steps continue for 30 to 40 cycles. The copied DNA can be used as the material to run in gel electrophoresis experiments. Gel electrophoresis allows DNA fragments, cut in specific location by restriction enzymes, to be separated based on size. c.) In combination, these two techniques are used in DNA fingerprinting, paternity testing, HIV testing, drug development, detection of mutations, and genetic sequencing.
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