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.
Answer:
The mechanisms of transport across the cell membrane are as follow: 1- simple diffusion, 2- facilitated diffusion, 3- primary active transport and 4-secondary active transport
Explanation:
The cell membrane is a selectively permeable structure capable of transporting substances by different mechanisms. Simple diffusion is a type of passive transport (i.e. does not require energy) where non-polar molecules (e.g. O2, CO2) pass across the membrane by a process that does not require energy from the cell. Facilitated diffusion is another type of passive transport where larger polar molecules (e.g., glucose and amino acids) pass across the membrane by using specific transmembrane integral proteins. On the other hand, primary active transport is a type of active transport that uses chemical energy (e.g., ATP) to move substances such as metal ions (Na+, K+, Ca2+) across the cell membrane against their concentration gradient. Finally, secondary active transport is another type of active transport where transporter proteins are used to couple the movement of ions (e.g., H+ protons) down their electrochemical gradient to the transport of another ions/solutes against their concentration/ electrochemical gradient.
Sensory neurons are types of brain cells that convert the stimuli coming from the senses (hearing, touch, smell, taste, and sight) into information that would allow the brain to interpret it as a sensation. For example, they convert the messages from the optical nerve if the object is of a light color or not.
Answer:
Mitosis and meiosis are similar at the level of writing, and possess a very close mechanism; however, they do not achieve the same result!
Mitosis corresponds to a single "asexual" cell division of somatic cells (almost all cells in the body), and clones two daughter cells from a mother cell, which will be identical, and inherit exactly the same heritage genetic, indeed these two daughter cells will each have an identical karyotype (same chromosomes) and an identical genotype (same alleles) to that of the mother cell.
Meiosis corresponds to two successive "sexual" cell divisions affecting only germ cells; starting from a diploid cell (chromosomes present in pairs), meiosis leads to the formation of four gametes (haploid sexual cells, spermatozoa or oocytes) (a single copy of the chromosomes). Then, during fertilization, two gametes (each from meiosis, in the male and female) come together to form a zygote, in which diploidy will be restored.
The right answers are:
create two identical cells ==> mitosis
create four non-identical cells ==> meiosis
create haploid cells ==> meiosis
creates diploid cells ==> mitosis
occurs in all cels other tha gametes ==> mitosis
occurs in all cells related to sexual reproduction ==> meiosis
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Explanation:
Answer:
crossing over
Explanation:
Crossing over is where homologs can exchange DNA which leads to genetic variation
