The document discusses the Ac-Ds transposable element system in maize and complementation testing. It notes that Ac is an autonomous transposable element that enables the movement of Ds elements. McClintock discovered that Ac, Ds, and the C gene are responsible for color instability in maize seeds. Complementation testing determines if two recessive mutations represent alleles of the same gene or different genes.

1. COMPLEMENTATION
TEST; AC – DS
SYSTEM IN
MAIZE

2. AC –DS SYSTEM
• Ac/Ds transposable controlling
elements was the first
transposable element system
recognized in maize.
• The Ac Activator element is
autonomous, whereas the Ds
Dissociation element requires an
Activator element to transpose.
• Ac was initially discovered as
enabling a Ds element to break
chromosomes.

3. • 4563 base pairs in length and Ds
elements are Ac elements that have
undergone deletions. Ds elements move
only in presence of Ac elements.
• Mc clintock identified that
two controlling elements Ac &
Ds and C gene are responsible
for genetic instability of corn
seed colour (purple, dotted, &
yellow).

4. • Transposable elements also called as
controlling elements, jumping genes, mobile
genetic elements or transposons are DNA
sequences that move from one location in the
genome to another.
• The process by which these sequences are
copied and inserted into new site in the
genome is called transposition and the
enzyme is known as transposase.

5. If reversion of c to C occurs ( Ds
again comes out of C gene insertion
site) and cell will produce purple
pigment and a spot seeds.

7. COMPLEMENTATION TEST
• Complementation test, also called cis-trans
test, in genetics, test for determining
whether two mutations associated with a
specific phenotype represent two different
forms of the same gene (alleles) or are
variations of two different genes.
• The complementation test is relevant for
recessive traits (traits normally not present
in the phenotype due to masking by a
dominant allele).

8. • In instances when two parent organisms
each carry two mutant genes in a
homozygous recessive state, causing the
recessive trait to be expressed, the
complementation test can determine
whether the recessive trait will be
expressed in the next generation.