Seymour Benzer used phage T4 mutants, Experimental
evidence that a gene is a linear sequence of nucleotide pairs. Some regions of
chromosomes have "hot spots" for mutations. Benzer's experimental
approach to fine structure mapping of the rII locus. Generated 1612 spontaneous point mutations
and several deletions in rII locus identified two complementation groups, rIIA
and rIIB. Mapped locations of deletions
relative to each other using recombination.
Mapped locations of point mutations relative to the deletions. Tested
for recombination between all point mutations within the same complementation
group.
Answer:
If an individual Drosophila has two or more populations of cells comprising different genotypes from one single egg then it is termed as twin spots or mosaic.
Explanation:
There might be different reasons for mosaic to occur like
Nondisjunctioning of the chromosomes
Lag in anaphase
Endoreplication
Mutations in a single cell
Mitotic recombination:
One of the major ways through which mosaic or twin spots arise is the mitotic recombination. It is also termed as somatic cross over. Twin spot or mosaic generally occurs if there is linking of heterozygous genes in repulsion. The recombination generally happens among the centromeres from the adjacent genes.
A common example of the mitotic recombination is the Bloom's syndrome. Bloom's syndrome is caused due to the mutation that occurs in the <em>blm</em> gene. As a result, there are defects in the BLM protein produced.
The nucleus tells the cell what to do, and also contains chromosomes, which has the cell's genetic material.
The genetic code is considered universal because the same four nucleotide bases are used by all known organisms
