In animals, sexual reproduction involves combining haploid nuclei from one egg a

Question

In animals, sexual reproduction involves combining haploid nuclei from one egg and one sperm to generate a diploid zygote. In contrast, parthenogenesis involves the generation of offspring from an unfertilized egg. Individuals generated by parthenogenesis have a single parent. These offspring carry only halfthe genetic complement of that parent, since part of the process of parthenogenesis involves generating two identical copies of each of the chromosomes present in the haploid egg.

Q1. From the point of view of gene variability and the adaptability of the population, what potential disadvantage might be associated with animals generated by parthenogenesis?

Q2. While parthenogenesis has been described in many animal species, including bees, fish, birds and lizards, it appears to be absent from mammalian species. However, in 2003 scientists from Tokyo and Seoul reported the successful generation of a mouse by parthenogenesis. The mouse has a similar immune system to that of humans, (as discussed in class). Also, as in humans, there is considerable variability in MHC proteins (and their corresponding genes) between different mice. How then might the capacity to generate mice by parthenogenesis influence our ability to match tissues for organ transplantation in mice?

Explanation / Answer

Q1- Genetic exchange does not take place in animals generated by parthenogenesis. This is the potential disadvantage associated with it. They lack genetic diversity. Unless an animal can recombine the DNA they already have, they will produce an offspring with an identical set of chromosomes, in which any genetic weakness, such as disease susceptibility or physical mutation, would have no chance to be overridden by outside genetic material from a mate.

Q2- The capacity to generate mice by parthenogenesis influence our ability to match tissues for organ transplantation in mice. Mouse embryos with two maternal genomes (diploid parthenogenetic (PG) embryos, or gynogenetic (GG) embryos with two maternal genomes from different oocytes fail early post implantation due to poor development of extraembryonic tissues, and rarely develop as far as later (20

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