Mendelism Questions in English

(B) The correct statement is $B$.
$A$ back cross is defined as the cross of an $F_1$ hybrid with either of its parents ($P_1$ or $P_2$).
$A$ test cross is a specific type of back cross where an individual of unknown genotype (usually $F_1$ or $F_2$ generation) is crossed with a homozygous recessive parent.
Since a test cross is a subset of back crosses,it is correct to say that every test cross is a back cross,but not every back cross is a test cross.

(D) sex has no influence on the dominance of traits.
Mendel's observation that reciprocal crosses produce identical results led him to conclude that the inheritance of traits is not influenced by the sex of the parent.
This means that the dominance of a trait is independent of whether the allele comes from the male or female parent,leading to the conclusion that sex has no influence on the dominance of traits.

(C) Gregor Mendel studied $7$ pairs of contrasting traits in pea plants.
Among the given options,the recessive characters are: white flower color,constricted pod shape,yellow pod color,terminal flower position,dwarf plant height,wrinkled seed shape,and green seed color.
Therefore,$C$ (White flower) is the correct answer as it is a recessive trait,whereas inflated pod,green pod color,and axillary flower position are dominant traits.

(A) . Leaf shape
Mendel studied $7$ pairs of contrasting characters in pea plants. Leaf shape was not one of them. The characters studied by Mendel are summarized below:

$S. No.$	Character	Dominant Trait	Recessive Trait
$1.$	Plant height	Tall	Dwarf
$2.$	Flower colour	Purple	White
$3.$	Flower position	Axial	Terminal
$4.$	Pod shape	Inflated	Constricted
$5.$	Pod colour	Green	Yellow
$6.$	Seed shape	Round	Wrinkled
$7.$	Seed colour	Yellow	Green

(A) Assertion $A$ is correct because in Mendel's monohybrid cross between a pure tall plant $(TT)$ and a pure dwarf plant $(tt)$, all $F1$ progeny are heterozygous tall $(Tt)$.
Reason $R$ is also correct because stem height is indeed a contrasting trait where the tall allele $(T)$ is dominant over the dwarf allele $(t)$.
Since the $F1$ generation expresses only the dominant trait (tallness), the reason $R$ correctly explains why all $F1$ plants are tall and none are dwarf.
Therefore, both $A$ and $R$ are correct and $R$ is the correct explanation of $A$.

(C) Step $1$: Statement $I$ is true. $A$ test cross is defined as the cross between an individual with a dominant phenotype (but unknown genotype) and a homozygous recessive parent to determine the genotype of the dominant individual.
Step $2$: Statement $II$ is false. In a test cross, if the unknown organism is homozygous dominant $(AA)$, all offspring will show the dominant trait $(Aa)$. If the unknown organism is heterozygous $(Aa)$, the offspring ratio will be $1:1$ (dominant to recessive). The ratio does not indicate the organism is homozygous dominant; rather, a $1:1$ ratio indicates it is heterozygous, and a $100\%$ dominant ratio indicates it is homozygous dominant.
Step $3$: Therefore, Statement $I$ is true and Statement $II$ is false.