DNA is essentially a storage molecule. It contains all of the instructions a cell needs to sustain itself. These instructions are found within genes, which are sections of DNA made up of specific sequences of nucleotides. In order to be implemented, the instructions contained within genes must be expressed, or copied into a form that can be used by cells to produce the proteins needed to support life.
The instructions stored within DNA are read and processed by a cell in two steps: transcription and translation. Each of these steps is a separate biochemical process involving multiple molecules. During transcription, a portion of the cell's DNA serves as a template for creation of an RNA molecule. (RNA, or ribonucleic acid, is chemically similar to DNA, except for three main differences described later on in this concept page.) In some cases, the newly created RNA molecule is itself a finished product, and it serves an important function within the cell. In other cases, the RNA molecule carries messages from the DNA to other parts of the cell for processing. Most often, this information is used to manufacture proteins. The specific type of RNA that carries the information stored in DNA to other areas of the cell is called messenger RNA, or mRNA.
How does transcription proceed?
Transcription begins when an enzyme called RNA polymerase attaches to the DNA template strand and begins assembling a new chain of nucleotides to produce a complementary RNA strand. There are multiple types of types of RNA. In eukaryotes, there are multiple types of RNA polymerase which make the various types of RNA. In prokaryotes, a single RNA polymerase makes all types of RNA. Generally speaking, polymerases are large enzymes that work together with a number of other specialized cell proteins. These cell proteins, called transcription factors, help determine which DNA sequences should be transcribed and precisely when the transcription process should occur.
<span>The geologic time scale is divided into periods, which are then divided into epochs, which are further divided into ages. For example, the time of the dinosaurs lasted 3 periods (Triassic, Jurassic, Cretaceous), each period had 3 epochs (late, early, middle), and each age fit into one of those. Many epochs have more than 1 age associated with them.
As for the basis for differentiating the eras, I'm not so sure. The only one I can say for sure is the end of the Cretaceous, which is when the dinosaurs suddenly became extinct due to a meteor impact. I think the divisions are based on significant, global-scale events that changed the world.
Sorry its so long but that the answer i think >:) ur welcome
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Answer:
Metaphase I
Explanation:
Homologous chromosomes are paired to facilitate crossing over during prophase I of the meiosis I. This is followed by alignment of homologous chromosomes at the equator of the cell during metaphase I. The process is assisted by microtubules of spindle apparatus. The kinetochore microtubules of the spindle apparatus attach themselves to the kinetochores of chromosomes.
The two sister kinetochores of duplicated homologous chromosomes are attached to the opposite pole to align the homologous pair at the center of the cells. Metaphase I is followed by anaphase I during which homologous chromosomes move towards the opposite poles.
Homeostasis, it is the process of organisms regulating their internal conditions. <span />
The geologic features that help scientists to determine the relative ages of rocks by their positions include index fossils, intrusions, and cross-cutting relationships (Option d).
<h3>What does geological age mean?</h3>
The expression geological age refers to the relative age of a given rock and or fossil (i.e. a piece or trace of dead organism) in a geological time scale.
In conclusion, the geologic features that help scientists to determine the relative ages of rocks by their positions include index fossils, intrusions, and cross-cutting relationships (Option d).
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