Monohybrid Cross - Heredity & Evolution, Science Video Lecture - Class 10

a monohybrid cross is one which involves
only one trait for this example we'll
look at stem high impedance and let's
say that you were told that tall people
ants were dominant two dwarf P plants
typically you'll represent the tall a
little therefore the dominant one with
an uppercase letter such as the
uppercase T and the dwarf with a
lowercase letter because it's recessive
so we'll use a lowercase T
so let's say that you're asked across a
heterozygous tall plant with a dwarf map
each plant needs to have a genotype and
the genotype is going to be made up of
two alleles in the case of the
heterozygous tall plant because it's
heterozygous it indicates the two
alleles are different for the dwarf
plant the two alleles would be the same
as that's the only way that you could
get a recessive phenotype after you've
identified the genotypes you need to
show the gametes produced from each
plant in the case of the heterozygous
one gamete might have an uppercase T
another a lowercase T but from the dwarf
you would only get lowercase t gametes
the gametes are produced through meiosis
and therefore have only one allele
from the gametes you can produce a
Punnett grid or sometimes known as a
Punnett square to show the probability
of certain outcomes in terms of the
genotypes of the offspring
so by adding together the alleles from
the gametes of the parents you can start
to see the outcomes
first of all the genotypic ratio would
be 50% uppercase T lowercase T and 50%
lowercase T lowercase T the uppercase T
lowercase T is obviously heterozygous
lowercase T lowercase T homozygous for
the phenotypic ratio you have 50% tall
plants that came from the uppercase T
lowercase T and 50% dwarf plants and
that came from the lowercase T lowercase
T