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Engineering HSC and IIT-JEE Mains an
advance videos. Hello students today we
are studying chapter
genetic basis of inheritance today we'll
be studying topic back cross back cross
means f1 hybrid meeting with its parents
let's study how.
Back Cross Mendel did all his
experiments using monohybrid cross that
is single crosses that have your process
that is crosses with two different
characteristics he also did a cross
which is termed as a cross now in that
cross what Mendel did was he crossed his
f1 progeny or his f1 generation with any
one of the parent so either he did it
crossed his f1 progeny with on f1
generation with the recessive parent or
sometimes he crossed his f1 progeny with
his dominant pens now when he crossed
his f1 progeny with the recessive parent
it was called as a test cross when it
will then experiment certain point in
time Mendel crossed his f1 hybrid with
the dominant Penan certain point of time
he comes to a phone generation with the
recessive pen
now the reason to do all this was just
to improve the quality of a crop just to
study the variations Mendel did this
along with that it was also possible to
see the desired genotype or we can see
the different changes and gamax when you
reversed and cross all this gamuts this
reverse analysis work just to confirm
certain laws of Mendel and also to find
what are the permutation orders would be
the outcomes if you reverse cross all
these things
backcross now when I talk about black
cross
it is a cross between the f1 hybrid and
any one of the parent or an individual
with either of the patented genotype
example the f1 hybrid could be crossed
with the dominant arm which is capital T
capital T in the case if we are
measuring the length or the height of
the plant or it could be crossed with
the small T small T depending upon what
we are measuring in the case of wrinkled
or rounding the dominant and the
recessive parents could be different
across of the f1 hybrid with the
recessive parent is also called as a
crest cross now test cross it is called
just to find out the progeny of that
generation but test cross is always a
back cross
one of these experiments which is shown
below is an example of a back cross or
you can say test cross now what Mendel
did in this was he took up their parent
of your tall parent which has capital T
and capital T and he crossed it with an
f1 hybrid which is capital D and smartly
now once he got the gamete segregated
and crossed them the result that mental
obtained was capital T capital T and
capital T small T now we all know that
capital D is always dominant and the
progeny should Finity picked appearance
which was tall and the genotypic ratio
or against the genotypes was something
like this capital T capital T and
capital T small T now the reason to do
back cross and test cross were the two
main reasons one this method is a rapid
method for improving the variety of a
car you can take the best species and
cross the pure species with the pure
species to get out the best rate once
metal did that he obtained one of the
good strengths in planets apart from
that this method can also be used to
obtain desirable changes in genotype for
example you can choose any hybrid and
cross it with the pure hybrid just to
observe the genotypic change and the
phenotypic change and to cross check the
various generations to come down to a
result or a conclusion students
whenever middle did this cross test or
we can say back cross or test cross if
you say he always made sure that he
choose an f1 generation with a pure plan
for example in certain cases he used a
pure love that is maltese malti with a
hybrid / that is capital T capital T now
in this case the results were capital T
small T and small T small T the ratio
was 1 is to 1 so by doing this he came
down to few conclusions and few results
I hope you are clear with this concept
of backcross thank you
