Answer: c.Natural selection is the process by which organisms with more beneficial traits are more likely to survive and reproduce.
Natural selection is the differential survival and reproduction of individuals because of differences in the phenotype. Phenotypic characteristics favors the survival of some organisms in the population better than others. Example given by Darwin population of colored beetles green and red belonging to same species. Green ones mimic the color of grass not noticed by birds but red ones were noticed and eaten by birds. This is the selection by nature for better suited individuals. Green color gave the survival advantage to these beetles which is a phenotypic characteristic therefore, they will produce more offsprings than the red ones and also pass on the phenotypic trait to their offsprings.
The pluripotent, undifferentiated cells in the bone marrow that give rise to the formed elements are called stem cells.
Pluripotent stem cells have the ability to undergo self-renewal and to give rise to all cells of the tissues of the body. However, this definition has been recently complicated by the existence of distinct cellular states that display these features.
There are two types of pluripotent stem cells :
- Embryonic stem cells (ESCs)
- Induced pluripotent stem cells
Embryonic stem cells are derived from the inner cell mass (ICM) of pre-implantation embryos and can be indefinitely maintained and expanded in the pluripotent state in vitro. Pluripotent stem cells can also be obtained by inducing dedifferentiation of adult somatic cells through a recently developed in vitro technology, known as cell reprogramming.
Similarly to Embryonic stem cells , Induced pluripotent stem cells can be expanded indefinitely and they are capable to differentiate in all the derivatives of the three germ layers.
Another intriguing features of being pluripotent is its reliance on gene expression heterogeneity.
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Answer:
Most restriction enzymes recognize sequences of 20-25 bp in length
Explanation:
Sequences of DNA that are recognized by restriction enzymes are called recognition (or restriction) sites are usually are between 4 and 8 bases long. Many of them are palindromic, which means that they are the same when you read it backwards and forwards (mirror-like).
Restriction enzymes are endonucleases, which means they cut phosphodiiester bonds within DNA. These enzymes are from prokaryotic organisms (archea and bacteria) which use them as defending mechanism against viruses. Prokaryotes protect their own DNA via methylation, performed by methyltransferase.
The mechanism of enzymatic action within a single substance
