Example of multi cropping is tomatoes+onions+marigold
        
             
        
        
        
Answer:In the nucleus of each cell, the DNA molecule is packaged into thread-like structures called chromosomes. Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure.
Chromosomes are not visible in the cell’s nucleus—not even under a microscope—when the cell is not dividing. However, the DNA that makes up chromosomes becomes more tightly packed during cell division and is then visible under a microscope. Most of what researchers know about chromosomes was learned by observing chromosomes during cell division.
Each chromosome has a constriction point called the centromere, which divides the chromosome into two sections, or “arms.” The short arm of the chromosome is labeled the “p arm.” The long arm of the chromosome is labeled the “q arm.” The location of the centromere on each chromosome gives the chromosome its characteristic shape, and can be used to help describe the location of specific genes.
 
        
             
        
        
        
Answer:
a. most genes encode one polypeptide and can be operationally defined by the complementation test
Explanation:
Genes are the stretch of DNA that code for specific polypeptides. In general, one gene codes for the only polypeptide. 
Genes are defined by complementation tests which in turn tell if two mutations have occurred in the alleles of the same gene or different gene. 
For the purpose, an organism with the homozygous genotype for one recessive mutation is crossed with an organism having the homozygous recessive genotype for another mutation. 
If the two mutations are in the same gene, the progeny would show the mutant phenotype. On the other hand, if two mutations are in different genes, the progeny would exhibit normal phenotype.