Answer:
By the end of prophase, each of the following has occurred except <em>lining up of chromosomes in the cell.</em>
Explanation:
The lining up of the chromosomes in the cell occurs during the third stage of cell division. This stage is termed as the metaphase.
Prophase is the first stage of cell division. Hence, the lining of the chromosomes does not occur by the end of prophase.
During the prophase, the chromatin material condenses and become more compact so that the chromosomes become visible. The nucleolus and the nuclear envelope disappear by the end of prophase. Hence, all other options A, B and C occur by the end of prophase except option D.
Answer:
The correct answer will be option-A
Explanation:
Desert biomes are characterised by the presence of the arid conditions or with few or less amount of rainfall.
The plant groups called the bryophytes and pteridophytes are dependent on the water for their fertilization which allows completing their life cycle.
In the desert conditions provided in the question, the mosses and ferns survived for many generations as these plant groups produced sperms with flagella which helped the sperms to swim in the water provided by the 10-inch rainfall per year and reach the female gamete and fertilize the egg cell.
Thus, option-A is the correct answer.
Answer:
The correct answer is ''undergo irreversible repression.''
Explanation:
The morphological and physiological transformation of meristematic cells into adult or differentiated tissues constitutes the process of cell differentiation. This, and the consequent specialization of the cell, bring about the division of labor, forming cells with specific functions. Differentiation occurs by differential activation of some genes and repression of others. Depending on the position it occupies, each cell receives certain stimuli to develop the corresponding activities. During the differentiation process, cells undergo a series of changes in their characteristics and there is a readjustment in their mutual relationships.Different molecular factors initiate and drive the programming / reprogramming of cell fate through the modulation of specific genomic and epigenomic patterns, which regulate the expression of activator / repressor genes of the main fundamental and specialized cellular processes. Thus, the differentiated cell will express certain genes and acquire certain functions.Adult stem cells are responsible for maintaining the different types of specialized cells that make up the body. Asymmetric cell division in stem cells has emerged as one of the main physiological mechanisms that regulate the number of cells and their diversity to maintain tissue homeostasis. A large number of molecules, generically called determinants of cell fate, participate in the regulation of asymmetric division. Asymmetric division of somatic stem cells produces both a stem cell and a progenitor. The initial progenitor cells, through new cycles of asymmetric cell division, finally reach their terminal state of cell differentiation, due to changes in intracellular and extracellular (environmental) signaling. After cells leave their mother state and begin to differentiate, they make exclusive selections for phenotypic pathways through secondary genomic / epigenomic modifications, mainly to different types and gradients of transcription factors (physiological programming of cell differentiation). This leads, for example, to activation of specialized biosynthetic pathways, remodeling of the cytoskeleton, and repression of cell proliferation signaling. The expression of genes is regulated mainly at the level of their transcription. Transcription factors correspond to proteins with the ability to interact with specific DNA sequences and trigger their transcriptional activity. Most transcriptional factors contain different domains that participate in different aspects of protein function; they generally contain two domains: a domain that binds to specific DNA sequences and an activation domain that regulates transcription by interacting with other proteins. In the regulation of gene transcription, in addition to transcription factors, coactivating and corepressor molecules participate, which bind to them, modifying their activity in a positive or negative sense. Each cell type has a characteristic pattern of gene transcription, which is determined by the binding of combinations of transcription factors to the regulatory regions of a gene.
The process of cellular respiration is achieved in plants by the process of photosynthesis. The energy from glucose is derived in this process. The steps of the cellular respiration includes the glycolysis, the kreb's cycle, and the oxidative phosphorylation. During this process, the proton concentration builds in the thylakoid space of the plant cell.
