Answer:A. The release of calcium ions causes myosin and actin to attach to each other.
The contraction of skeletal muscles takes place by induction of a nerve impulse, which produces a movement and the interaction of the filaments containing proteins named as actin and myosin. This interaction of filaments is regulated by proteins called tropomyosin and troponin present on the actin filaments. The motor nerve causes the depolarization of the muscle membrane sarcolemma. This triggers the sarcoplasmic reticulum to release calcium ions. This calcium binds to troponin and thus allows the tropomyosine strand on the actin filament to displace so that the part of the actin where myosine head needs to be attached remain uncovered. Binding of the actin myosine filament results in contraction.
Hence, the release of calcium ions causes myosin and actin to attach to each other causes muscle contraction.
I believe it is B. Thermosphere
Correct me if wrong.
DNA and RNA each contain four nitrogenous bases. They have 5 not 4.
Hi
Below are five major steps of DNA or gene cloning:
1: You chose the gene or specific piece of DNA you need to clone and cut the gene with restriction enzymes from the source organism.
2: You need to choose a vector for the process of cloning and you will cut the vector with same restriction enzymes through which you have cut your target DNA sequence to be inserted into the vector.
3: You place the target gene into the vector and join or seal the gene with vector by using an enzyme called DNA ligase.
4: You introduce the vector with your target gene into a suitable host organism such as yeast or bacteria through the process of Transformation. In this process host organism takes up the vector containing your target gene and starts replicating the target DNA along with their own DNA and thus creating millions of copies of target gene .
5: In the last step, the DNA or target gene is isolated from host organism and purified and is ready to be used since its quantity has been enormously increased through the process of cloning.
The cloning is also called as recombinant DNA technology and is the main process that is being used in the production of insulin for diabetes patients. You can see below image for better understanding.
Hope it help!