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....
B) the amount of available resources
frequency of the dominant allele in the population ... 2pq = frequency of heterozygous individuals. A population of rabbits may be brown (the dominant phenotype) or white (the recessive phenotype). Brown rabbits have the genotype BB or Bb. White rabbits have the genotype bb.
Black stuff from volcanos!
