Monohybrid Cross Video Lecture - NEET

the Mendeley and cross is named for
gregor mendel a nineteenth-century
Augustinian monk who performed and
documented the first controlled genetic
crosses and allowed humanity to begin to
understand the nature of inheritance
very welcome a Mendelian cross begins
with a controlled breeding experiment
spanning at least three generations and
is designed to determine the inheritance
pattern of a trait now here's some
terminology to help us describe these
crosses we call the outward appearance
of a trait its phenotype the phenotype
of this flower is purple each version of
a gene is called an allele the examples
in this video will have two types of
alleles dominant represented by an
uppercase letter or recessive
represented by a lowercase letter the
combination of alleles and individual
carries is called the genotype P plants
have two copies of each gene so the
genotype of each trait is represented by
two alleles the next concept to
understand is that every Mendel Ian
cross begins with true breeding parents
true breeding means that if two
individuals of that variety of organism
are mated then all the progeny will
resemble the parents for a particular
trait in this case white flowered
parents always produce white flowered
progeny now let's start the Mendelian
cross the initial parents in a Mendeley
and monohybrid cross will be true
breeding individuals who differ from one
another by a single trait such as these
P plans one of which has a purple flower
and the other has a white flower when it
comes time to cross the two individuals
they'll be bred in a reciprocal cross
now this means that pollen from the
purple flower plant will be placed on
the stigma of the white flowered plant
making the mother in this cross white
and the father purple a second cross is
also initiated where pollen is taken
from the white flowered plant and placed
on the stigma of the purple flowered
plant so the mother has
purple flowers and the father white
flowers this type of cross is set up to
ensure that the trade is truly inherited
from both parents equally any progeny
produced from the true breeding parents
and Amanda Lee and cross are called the
f1 progeny or f1 generation all the
progeny in a cross like this will
resemble one of the parents regardless
of the parental phenotype the parental
variety seen amongst all the f1 progeny
is considered the dominant trait the
parental variety that is absent in the
f1 is the recessive trait so for this
cross purple flower color is dominant
and white is recessive
Amanda lien Kraus will continue for at
least one more generation for the next
cross two of the purple f1 progeny are
chosen and crossed with one another this
means that the mother and father are
actual siblings produced from the
parental cross any progeny produced by
this cross is called the f2 generation
in this generation three-quarters of the
progeny will have the dominant version
of the trait and one quarter will have
the recessive demonstrating that the
recessive trait didn't disappear but was
hidden in the f1 generation let's start
over and explain these patterns using
chromosomes and alleles each individual
has two alleles or copies of each gene
and they reside on the homologous pairs
of chromosomes that segregate during
meiosis
for example the parental purple flower
plant will have two copies of the
dominant gene represented here by
uppercase letter P chosen to represent
purple this combination is called
homozygous dominant the white flower
plant has two copies of the recessive
gene represented here by a lowercase P
chosen to represent a lack of purple
pigment this is called homozygous
recessive the f1 receives one allele or
gene copy on a chromosome from each
parent
this combination of one dominant and one
recessive in the f1 progeny is called
heterozygous the f1 heterozygotes in
this cross will appear dominant because
they received one dominant allele from
the homozygous dominant parent in the f1
cross both parents are heterozygous so
progeny have the possibility to be
homozygous dominant
homozygous recessive
or heterozygous by two different
combinations of alleles
the homozygous dominant and heterozygous
progeny will express the dominant trait
and the homozygous recessive will appear
recessive these combinations of alleles
explain the three-to-one ratio typically
seen in the f2 generation all the
possible combinations of alleles in the
f2 generation can be predicted using a
punnett square a prediction tool devised
by Reginald Punnett in the first decade
of the 20th century what so in this
method we can put the two versions of
the gene from one parent along the top
of the four units Square and two
versions of the gene from the other
parent down the side of the four units
square the boxes in the middle are used
to predict every combination we notice
after filling it in that three of the
four possible combinations would produce
a dominant trait because they have at
least one dominant allele and one of the
four would produce a recessive trait
because it has two recessive copies
hey thanks for watching
you