The given question is incomplete, the complete question is:
A student carries out PCR using the following steps: Step 1: 94°C for 1 minute Step 2: 60°C for 30 seconds Step 3: 72°C for 30 seconds After subjecting his PCR reaction to gel electrophoresis, the student sees no PCR product on the gel. What error(s) might he have made? (Select all that apply.) a. He carried out step 1 at too low a temperature. b. He carried out step 1 at too high a temperature. c. He carried out step 2 at too low a temperature. d. He carried out step 2 at too high a temperature. e. He carried out step 3 for too short a time.
Answer:
The correct answers are options d and e, that is, the student might have carried the step 2 at too high temperature, and he would have carried the step 3 for a brief duration.
Explanation:
In the PCR, step 1 is termed as the denaturation step and it generally takes place at 94 or 95 degrees Celsius. Thus, option a and b are incorrect. In step 2 of the PCR reaction, the combination of primers takes place with the template, this step is known as the annealing step. The temperatures in the annealing step are important for PCR, if the temperature of annealing is too much, it can lead to no product formation, and if it is too less than the formation of products would be non-specific.
In step 3 of the PCR reaction, the temperature is extended and the Taq polymerase enzyme is used to perform the reaction, which supplements nucleotides to the newly developed stand, at the frequency of 1 kilobase pair per minute. If the product of PCR is one kilobase or more, then a 30 seconds extension time would be not enough and the product would fail to appear. Hence, the correct options would be d and e.
Answer;
They fused into Pangaea
By the close of the paleozoic era all the continents fused into Pangaea.
Explanation;
Paleozoic era is the era of "ancient life".
During the early Paleozoic era, South America, Africa, Australia, Antarctica, India, and perhaps China comprised the vast southern continent of Gondwana.
At the beginning of this period, all continents joined together to form the supercontinent Pangaea, which was encircled by one ocean called Panthalassa.
Answer: transcription, rna, rna polymerase
Explanation:
<u>Answer</u>:
If I were studying the causes of cancer, the topic which might interest me is "The topic of spindle-fibre structure.".
<u>Explanation</u>:
In cell division, the accurate segregation of chromosomes is coordinated with the complex structure of spindle fibre in cell. The mitiotic structure is consisted of two apparatus, one is centrosomes and the other is microtubules. Mitiotic spindle is formed during the polymerization process of the microtubules in centrosome. Any kind of disruption in the structure of the microtubules causes aberration in the spindle fibre structure and error in the number of chromosomes. This change is one of the major causes of developing cancer.
The ependymal cells is the answer. One of the four types of
neuroglia in the center of nervous system is ependymal, this is the reason of
production of cerebrospinal fluid, this cause to serve as a reservoir for
neuroregeneration, also this is made of thin neuroectodermal linange to
ventricular system of the brain and the central canal of the spinal cord, made
up of ependymal cells