In gel electrophoresis dna molecules migrate from to ends of the gel.

a, acidic basic
b, negative positive
c, basic acidic
d, long short
e, positive negative

b, negative ... positive

Explanation:

Gel electrophoresis is  a method used in molecular biology for DNA analysis. This method includes the separation of DNA fragments through the gel according to their size or shape under the influence of aplid electric current. Since the fragments of DNA are negatively charged, they will move from negative to positive end.

Small fragments will move faster than larger ones.

One of the major source of error is contamination of the DNA sample. This refers to the presence of foreign DNA in the sample of interest. As a consequence, the gel will have more bands.

Another errors might appear as a result of wrong concentration of the gel, wrong buffer pH, high/low concentration of dye etc.

regulation of gene expression. gene expression can be regulated by various cellular processes with the aim to control the amount and nature of the expressed genes. these regulatory proteins bind to dna and send signals that indirectly control the rate of gene expression

explanation:

the two answers are a, the population of birds with large beaks will increase on the island, and c, the trait for large beaks will be passed on to future generations through natural selection. the reason for that is because if the birds that have beaks developed for eating small seeds lose all of their food, they will go hungry and eventually starve because they physically cannot eat the large seeds, therefore making the population of large beaked birds higher. also, if the trait of large beaks are dominant on the island over small beaks, then over time the large beaked birds will reproduce more and more, while the smaller beaked birds will reproduce less and less because they can't survive with the food provided. that leads to the trait of small beaks disappearing and the trait of large beaks taking over the island.