Answer:
The C. elegans embryo is a powerful model system for studying the mechanics of metazoan cell division. Its primary advantage is that the architecture of the syncytial gonad makes it possible to use RNAi to generate oocytes whose cytoplasm is reproducibly (typically >95%) depleted of targeted essential gene products via a process that does not depend exclusively on intrinsic protein turnover. The depleted oocytes can then be analyzed as they attempt their first mitotic division following fertilization. Here we outline the characteristics that contribute to the usefulness of the C. elegans embryo for cell division studies. We provide a timeline for the first embryonic mitosis and highlight some of its key features. We also summarize some of the recent discoveries made using this system, particularly in the areas of nuclear envelope assembly/ dissassembly, centrosome dynamics, formation of the mitotic spindle, kinetochore assembly, chromosome segregation, and cytokinesis.
1. The C. elegans embryo as a system to study cell division
The C. elegans embryo is a powerful model system for studying the mechanics of metazoan cell division. Its primary advantage is that the syncytial gonad makes it possible to use RNA interference (RNAi) to generate oocytes whose cytoplasm is reproducibly (>95%) depleted of targeted essential gene products. Introduction of dsRNA rapidly catalyzes the destruction of the corresponding mRNA in many different systems. However, depletion of pre-existing protein is generally a slow process that depends on the half-life of the targeted protein. In contrast, in the C. elegans gonad, the protein present when the dsRNA is introduced is depleted by the continual packaging of maternal cytoplasm into oocytes (Figure 1). Since depletion relies on the rate of embryo production instead of protein half-life, the kinetics tend to be similar for different targets. By 36-48 hours after introduction of the dsRNA, newly formed oocytes are typically >95% depleted of the target protein.
Explanation:
Answer:
Changes that cannot be reversed are called irreversible changes
Example: if you cook an egg or if something goes bad. these changes can not be reversed.
Their reproductive isolation from each other is complete: False
They are unable to produce hybrid offspring upon interbreeding: True
They shared a common ancestor recently in evolutionary time: False
Explanation:
A species known as a group of that organisms which can be potentially interbreed with another one to produce viable, fertile offspring. Prezygotic and postzygotic barriers separated the species from each other. It prevents the mating of viable fertile offspring.
This process happens when groups in that species become reproductively diverge as well as isolated. In the formation of new species postzygotic and Prezygotic barriers play vital role.
<span>Species= a group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding. The species is the principal natural taxonomic unit, ranking below a genus and denoted by a Latin binomial.
</span><span>
Alpaca - Vicugna pacos
.Anole lizard - Anolis carolinensis.
Armadillo - Dasypus novemcinctus.
Bushbaby - Otolemur garnettii.
Cat - Felis catus.
Chicken - Gallus gallus.
Chimpanzee - Pan troglodytes.
Chinese hamster - Cricetulus griseus.</span>
