Answer:
The correct answer is: d. REs activity is best preserved by freezing the RE and thawing it out for brief periods of time as needed.
Explanation:
- Restriction enzymes can be defined as endonucleases that can recognize specific nucleotide sequence in a DNA (Deoxyribonucleic acid) sequence and cause breakage of phosphodiester bond in the DNA at the target site. Hence, it has the capacity of cleaving a DNA sequence.
- These are made up of proteins which are required to be present in the accurately folded conformation in order to function.
- Any form of alteration in the three-dimensional structure of the protein induced due to physical, chemical, mechanical or physiological factors can cause denaturation of the protein which in turn can render the protein non-functional.
- Freezing of restriction enzymes (REs) directly without the use of glycerol will cause the movement of water molecules within the proteins as well layering of water molecules on the protein surface.
- At low temperature these water molecules change to ice crystals which can alter the conformation of the protein or can cause breakage of peptide bonds in the proteins by physical force.
- This can cause the protein to get denatured and hence non-functional.
- Hence, it is never advisable to preserve REs by freezing directly without glycerol.
- Glycerol forms a layer around the protein molecules and prevents the protein molecules from coming into direct contact with the water molecules and hence prevents protein denaturation.
The Precambrian era envelopes the major bulk of the history of the Earth, beginning from the creation of the planet approx 4.5 billion years ago and terminating with the origination of composite, multicelled forms of life approximately 4 billion years after.
The Precambrian refers to the earliest of the geologic ages that are signified by the distinct layers of sedimentary rock. The Earth was about more than six hundred million years old when life started. The planet had cooled down from its native molten state, creating a solid crust and oceans formed by water vapor in the atmosphere.
At about three billion years ago, the atmosphere of the Earth was virtually devoid of oxygen. At approximately 2.4 billion years ago, oxygen was discharged from the seas as a waste product of photosynthesis by cyanobacteria. The levels of the gas slowly raised, attaining about 1 percent around two billion years ago.
Approximately 800 million years ago, the levels of oxygen attained about 21 percent and started to breathe life into more composite species. The oxygen-rich ozone layer was also created, protecting the surface of the Earth from the harmful solar radiation.
Answer:
A. A majority of scientists agreed with it
Explanation:
The famous theory called the theory of common descent, states that all the living organisms of the earth have arisen from a common ancestor. This notion was first proposed by a French mathematician,Louis Maupertuis duirng 1740s who was of the view that all organisms had a single ancestor and evolutionary process with the passage of time resulted in the specie diversification.
After that, in 1790s another philosopher Immanuel Kant, suggested that all organisms seem to have a common ancestor. In the same period of 1790s, another scientist , Erasmus Darwin who was the grandfather of Charles Darwin also suggested that all the organisms might have a single ancestor who went through the process of evolution to bring all the majesty into life.
Charles Darwin was the first scientist who worked on this notion for alot of time and proposed the theory of common descent,in his book, On the Origin of Species.
After it, many scientists got agree with this theory such as, Vernon Kellogg in 1907 and T. Ryan Gregory in 2008 and many others explain that no reliable observations exists which contradicts the theory of common descent.
Therefore, option A is the best option.
Hope it helps!
Answer:
The gonads are reproductive organs responsible for the production of <u>gametes (sex cells) in their external secretion and in their internal secretion, hormones that exert their action on the organs involved in reproductive function.</u>
Explanation:
Gonads are glands that are part of two body systems: the endocrine system and the reproductive system; and there are two types of gonads: male and female, the first are the testicles and the second the ovaries and both produce steroid hormones (derived from cholesterol) exactly the same as those produced by the cortex of the adrenal glands.
embryonic stem cells could serve as a model to evaluate the physiological effects of environmental pollutants efficiently and cost-effectively.
