You got me all the way fuqed
up son!
Accuracy describes how well a measuring instrument determines the variable it is measuring. How close the value is to real value. The level of accuracy of measuring tool determines the detail to which it can measure. In order to be accurate in their work scientists need first select a measuring instrument that allows an appropriate measure of accuracy and then to calibrate it. Calibrating an instrument involves measuring already known quantities to check how accurately it is. In the laboratory accuracy of a test is determined when possible comparing results from the test in question with results geenrated from an established reference method.
Answer:
I think you're referring to the Metaphase...
Explanation:
During Cell Division (or, rather before!) the DNA needs to be replicated. This normally is done by DNA Polymerase, and results in two identical double strands (the "Sister Chromatids".
These chromatids are held together at the Centromere, which will be the heart of the "X"-shape. After that the DNA is packed into Chromosomes by winding it around proteins called Histones. If I remember correctly there are 5 different Histones.
This "Zipping Up" makes the chromosomes more visible.
As the two sister chromatids are still connected, the result is the X-shaped Metaphase Chromosome....
