Chromosomes

the number of chromosomes in a animal doesn't mean anything in terms of intelligence etc. but is just the way the animals DNA is structured

Chromosomes 

DNA - holds genes, inheritable information

proteins - help in DNA replication 

homologous pairs - out of the chromosomes, have the same sequence of genes but can have different alleles, in that case the dominant allele shows in the organism 

usually chromosomes cant been seen but just before cell division they thicken up and can be seen and paired

sometimes during chromosomes copying (cell dividing) DNA can be changed, forming a mutation

mutations can have a  negative, positive or neutral effect on the organisim