At the smallest level of organization, the DNA wraps itself around small globular proteins called histones. Complexes of histones and DNA form nucleosomes, which appear as "beads" on the DNA strand. Chromatin refers to the decondensed DNA that has not formed separate chromosomes.
Answer:
Please see below
Explanation:
The number of chromatids have been stated with the respective event when it occurs in that particular number in the following way:
<u>23 chromatids</u>
primary oocyte arrested prior to ovulation
spermatozoa
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<u>46 chromatids</u>
oogonium prior to S phase
<u>92 chromatids</u>
secondary polar body
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:
Igneous rocks are classified by particle size
The cerebrum (brain) can be divided into two hemispheres: the left hemispheres and the right hemisphere. These hemispheres are separated by a deep longitudinal fissure (i.e., the cerebral fissure).
- In this case, the patient will be able to identify the cat using his RIGHT-HAND.
- The left brain hemisphere receives sensory information from and controls movements on the right part of the body, and vice-versa.
- In consequence, the left brain hemisphere controls the movements of the right hand, whereas the right brain hemisphere controls the left hand.
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