Multiple alleles Questions in English

(B) Self-sterility (also known as self-incompatibility) in $Nicotiana$ was first reported by $E.M. East$ in $1925$.
This phenomenon is controlled by a series of multiple alleles at a single locus,often denoted as the $S$-locus.
These alleles prevent self-fertilization,thereby promoting cross-pollination and increasing genetic diversity within the population.

(A) Alleles are slightly different forms of the same gene. They occupy the same locus on homologous chromosomes and control the expression of a specific trait (e.g.,tallness or dwarfness in pea plants). Therefore,they are defined as a pair of genes governing a specific character.

(D) The different forms of a gene that occupy the same locus on homologous chromosomes are known as alleles.
For example,in pea plants,the gene for height has two forms: one for tallness $(T)$ and one for dwarfness $(t)$.
These two forms ($T$ and $t$) are alleles of the same gene.

(A) The $ABO$ blood group system in humans is controlled by the gene $I$. This gene has three alleles: $I^A$,$I^B$,and $i$.
Since there are more than two alleles present for a single gene locus within a population,this phenomenon is known as multiple allelism.
Different combinations of these three alleles result in four distinct phenotypes: blood types $A, B, AB$,and $O$.

(C) The human $ABO$ blood group system is controlled by the gene $I$. The gene $I$ has three alleles: $I^A$,$I^B$,and $i$ (or $I^O$).
For blood group $A$,the individual can be homozygous $(I^A I^A)$ or heterozygous ($I^A i$ or $I^A I^O$).
Therefore,the possible genotypes for blood group $A$ are $I^A I^A$ or $I^A I^O$.

(D) The human $ABO$ blood group system is controlled by the gene $I$. The gene $I$ has three alleles: $I^A$,$I^B$,and $i$.
- Alleles $I^A$ and $I^B$ are codominant,while $i$ is recessive.
- $A$ person with blood group $B$ can have the genotype $I^B I^B$ (homozygous) or $I^B i$ (heterozygous),as the $I^B$ allele is dominant over the $i$ allele.

(C) The blood group $O$ is represented by the genotype $I^O I^O$.
Since the child inherits one allele from each parent,the child must have received one $I^O$ allele from the father and one $I^O$ allele from the mother.
Given that the father has blood group $B$,his possible genotypes are $I^B I^B$ (homozygous) or $I^B I^O$ (heterozygous).
Since the father must contribute an $I^O$ allele to the child to result in an $O$ blood group child,the father must be heterozygous for blood group $B$,which is $I^B I^O$.

(D) The genotype of a person with blood group $O$ is $ii$ (recessive).
The genotype of a person with blood group $AB$ is $I^A I^B$ (codominant).
When these parents cross,the possible offspring genotypes are $I^A i$ (blood group $A$) and $I^B i$ (blood group $B$).
Since the $O$ parent lacks both $I^A$ and $I^B$ alleles,they cannot pass these alleles to the offspring.
Therefore,it is impossible for the child to have the $AB$ blood group,as the child must inherit one allele from each parent.

(D) The inheritance of $ABO$ blood groups in humans is controlled by the gene $I$. The gene $I$ has three alleles: $I^A$,$I^B$,and $i$.
If one parent has blood group $A$ (genotype $I^A I^A$ or $I^A i$) and the other parent has blood group $B$ (genotype $I^B I^B$ or $I^B i$),the offspring can inherit different combinations of these alleles.
If both parents are heterozygous (genotypes $I^A i$ and $I^B i$),the possible genotypes for the offspring are $I^A I^B$ (blood group $AB$),$I^A i$ (blood group $A$),$I^B i$ (blood group $B$),and $ii$ (blood group $O$).
Therefore,the offspring can have any of the four blood groups: $A, B, AB,$ or $O$.

(C) The blood group of the father is $B$ and the mother is $A$. For the child to have blood group $B$,the father must be heterozygous $(I^B I^O)$ and the mother must be heterozygous $(I^A I^O)$.
According to the Punnett square:
- Father's gametes: $I^B, I^O$
- Mother's gametes: $I^A, I^O$
- Possible genotypes of children: $I^A I^B$ $(AB)$,$I^A I^O$ $(A)$,$I^B I^O$ $(B)$,$I^O I^O$ $(O)$.
Since the child has blood group $B$,the genotype must be $I^B I^O$.

(A) The two Mendelian factors that occur on the same locus in the two homologous chromosomes of an individual and control the expression of a trait or character are called alleles or allelomorphs. $A$ pair of these contrasting forms of a gene is referred to as allelomorphs.

(B) The genotype of a man with blood group $AB$ is $I^A I^B$,and the genotype of a woman with blood group $O$ is $ii$.
When these individuals cross,the possible genotypes for the offspring are $I^A i$ (blood group $A$) and $I^B i$ (blood group $B$).
Thus,the children will have either blood group $A$ or blood group $B$.
Since neither $A$ nor $B$ blood group matches the parents ($AB$ and $O$),the blood group of the children differs from both parents.

(C) Multiple alleles are defined as a series of three or more alternative forms of a gene that occupy the same locus on a specific chromosome in a population.
Since they occupy the same locus,they represent different states of the same gene and do not undergo crossing over between them.

(D) The genotype of the mother with blood group $AB$ is $I^A I^B$.
The genotype of the father with blood group $O$ is $ii$.
When these genotypes are crossed:
$I^A I^B \times ii$
The possible gametes from the mother are $I^A$ and $I^B$.
The possible gametes from the father are $i$ and $i$.
The resulting offspring genotypes will be $I^A i$ (Blood group $A$) and $I^B i$ (Blood group $B$).
Therefore,the possible blood groups of the child are $A$ and $B$.

(C) In a multiple allele system,although a population may have more than two alleles for a specific gene (e.g.,$ABO$ blood grouping in humans),an individual is diploid and carries only two alleles for that gene in their somatic cells.
However,during the process of gametogenesis,meiosis occurs,which results in the segregation of alleles.
Consequently,each gamete receives only one allele for a given gene.
Therefore,regardless of the number of alleles present in the population,a single gamete will always contain only one allele.

(A) The $ABO$ blood group system in humans is an example of multiple alleles.
There are three alleles: $I^A$,$I^B$,and $i$.
- $I^A$ and $I^B$ are codominant,while $i$ is recessive to both.
The possible genotypes are: $I^A I^A$,$I^A i$,$I^B I^B$,$I^B i$,$I^A I^B$,and $ii$.
The corresponding phenotypes are:
$1$. $I^A I^A$ and $I^A i$ result in blood group $A$.
$2$. $I^B I^B$ and $I^B i$ result in blood group $B$.
$3$. $I^A I^B$ results in blood group $AB$.
$4$. $ii$ results in blood group $O$.
Thus,there are a total of $4$ phenotypes $(A, B, AB, O)$.

(B) The blood group $A$ can have genotypes $I^A I^A$ or $I^A i$. The blood group $AB$ has the genotype $I^A I^B$.
Case $1$: If the parent with blood group $A$ is homozygous $(I^A I^A)$:
Cross: $I^A I^A \times I^A I^B$
Offspring genotypes: $I^A I^A$ (Blood group $A$),$I^A I^B$ (Blood group $AB$).
Case $2$: If the parent with blood group $A$ is heterozygous $(I^A i)$:
Cross: $I^A i \times I^A I^B$
Offspring genotypes: $I^A I^A$ (Blood group $A$),$I^A I^B$ (Blood group $AB$),$I^A i$ (Blood group $A$),$I^B i$ (Blood group $B$).
Combining both cases,the possible blood groups are $A, B,$ and $AB$.

(C) The genotype for blood group '$A$' can be $I^AI^A$ or $I^Ai$,and for blood group '$B$' can be $I^BI^B$ or $I^Bi$.
If the father is $I^Ai$ (heterozygous) and the mother is $I^BI^B$ (homozygous),the offspring will have $I^AI^B$ ($AB$ blood group) and $I^Bi$ ($B$ blood group),resulting in a $50\%$ probability of $AB$ blood group.
Similarly,if the father is $I^AI^A$ (homozygous) and the mother is $I^Bi$ (heterozygous),the offspring will have $I^AI^B$ ($AB$ blood group) and $I^Ai$ ($A$ blood group),which also results in a $50\%$ probability of $AB$ blood group.
Therefore,a $50\%$ probability of $AB$ blood group is obtained only when one of the parents is heterozygous and the other is homozygous.

(B) The $ABO$ blood group system in humans is controlled by three alleles: $I^A$,$I^B$,and $i$.
These three alleles result in the following genotypes: $I^A I^A$,$I^A i$,$I^B I^B$,$I^B i$,$I^A I^B$,and $ii$. Thus,there are $6$ possible genotypes.
The phenotypes produced are $A$,$B$,$AB$,and $O$. Thus,there are $4$ possible phenotypes.
Therefore,the number of genotypes is $6$ and the number of phenotypes is $4$.

(C) Multiple alleles refer to the presence of more than two alternative forms of a gene occupying the same locus on a homologous chromosome pair.
Since an individual is diploid,they can only carry two alleles at a time,but in a population,more than two alleles can exist for a specific trait.
An example of this is the $ABO$ blood grouping system in humans,which is controlled by the $I$ gene.

(B) In humans,$ABO$ blood grouping is controlled by the gene $I$. The gene $I$ has three alleles: $I^A$,$I^B$,and $i$.
$I^A$ and $I^B$ produce slightly different forms of sugar,while allele $i$ does not produce any sugar.
Alleles $I^A$ and $I^B$ are completely dominant over $i$,meaning when $I^A$ and $i$ are present,only $I^A$ expresses. However,when $I^A$ and $I^B$ are present together,they both express themselves due to codominance.
Thus,blood groups are controlled by $3$ alleles where $I^A$ and $I^B$ show codominance and are dominant over $i$.

(D) Genes that occupy the same locus on homologous chromosomes and control the same trait are known as $Alleles$ (or allelomorphs).
These are slightly different forms of the same gene that arise by mutation and are found at the same place on a chromosome.
Therefore,the correct option is $D$.

(D) The inheritance of $ABO$ blood groups is controlled by the gene $I$. The gene $I$ has three alleles: $I^A$,$I^B$,and $i$.
If the mother has blood group $B$,her genotype can be $I^B I^B$ or $I^B i$.
If the father has blood group $A$,his genotype can be $I^A I^A$ or $I^A i$.
Considering the heterozygous condition ($I^B i$ and $I^A i$),the cross is $I^A i \times I^B i$.
The possible genotypes of the offspring are $I^A I^B$ $(AB)$,$I^A i$ $(A)$,$I^B i$ $(B)$,and $ii$ $(O)$.
Therefore,all four blood groups $(A, B, AB, O)$ are possible in the offspring.

(A) Multiple alleles refer to the presence of more than two alternative forms of a gene occupying the same locus in a population.
In the case of $ABO$ blood grouping in humans,the gene $I$ exists in three allelic forms: $I^A$,$I^B$,and $i$.
Since an individual can only possess two of these alleles at a time,but the population contains three,it serves as a classic example of multiple alleles.
Starch grain size and seed shape in peas are examples of pleiotropy and simple dominance,respectively.

(B) $ABO$ blood grouping in humans is controlled by the gene $I$. The gene $I$ has three alleles: $I^A$,$I^B$,and $i$.
Since there are more than two alleles present for a single gene in a population,this phenomenon is known as multiple alleles.
While an individual only possesses two of these alleles,the presence of three different alleles in the population makes it a classic example of multiple allelism.

(D) The blood group $A$ can be represented by genotypes $I^A I^A$ (homozygous) or $I^A i$ (heterozygous). The blood group $AB$ is represented by the genotype $I^A I^B$.
If the man is homozygous $(I^A I^A)$,the cross is $I^A I^A \times I^A I^B$,resulting in offspring with genotypes $I^A I^A$ (Group $A$) and $I^A I^B$ (Group $AB$).
If the man is heterozygous $(I^A i)$,the cross is $I^A i \times I^A I^B$,resulting in offspring with genotypes $I^A I^A$ (Group $A$),$I^A I^B$ (Group $AB$),$I^A i$ (Group $A$),and $I^B i$ (Group $B$).
The presence of an offspring with blood group $B$ $(I^B i)$ confirms that the father must have contributed the $i$ allele,meaning he is heterozygous $(I^A i)$.

(D) The inheritance of human blood groups is controlled by the $I$ gene,which has three alleles: $I^A$,$I^B$,and $i$.
If the parents are heterozygous for their respective blood groups (i.e.,$I^A i$ and $I^B i$),the possible genotypes for the offspring are determined by a Punnett square cross:
$I^A i \times I^B i \rightarrow I^A I^B$ (Blood group $AB$),$I^A i$ (Blood group $A$),$I^B i$ (Blood group $B$),and $ii$ (Blood group $O$).
Therefore,the offspring can have any of the four blood groups: $A, B, AB,$ or $O$.

(A) The genotype of the mother with blood group '$A$' can be $I^A I^A$ or $I^A i$.
The genotype of the father with blood group '$AB$' is $I^A I^B$.
Case $1$: If the mother is $I^A I^A$,the cross is $I^A I^A \times I^A I^B$. The offspring genotypes are $I^A I^A$ (Blood group '$A$') and $I^A I^B$ (Blood group '$AB$').
Case $2$: If the mother is $I^A i$,the cross is $I^A i \times I^A I^B$. The offspring genotypes are $I^A I^A$ (Blood group '$A$'),$I^A I^B$ (Blood group '$AB$'),$I^A i$ (Blood group '$A$'),and $I^B i$ (Blood group '$B$').
Combining both cases,the possible blood groups for the children are '$A$','$B$',and '$AB$'.

(B) The cross between the parents with genotypes $I^AI^B$ and $I^Ai$ results in the following offspring genotypes:

$I^A I^A$	Genotype $I^A I^A$ (Phenotype $A$)
$I^A i$	Genotype $I^A i$ (Phenotype $A$)
$I^A I^B$	Genotype $I^A I^B$ (Phenotype $AB$)
$I^B i$	Genotype $I^B i$ (Phenotype $B$)

As shown above,there are $4$ distinct genotypes $(I^AI^A, I^Ai, I^AI^B, I^Bi)$ and $3$ distinct phenotypes $(A, AB, B)$.

(A) : Genes are the units of inheritance and contain the information that is required to express a particular trait in an organism.
Alternating forms of a single gene which code for a pair of contrasting traits are known as alleles.
For example,two alleles determine the height of a pea plant (tall and dwarf).

(A) Multiple alleles refer to the existence of more than two alternative forms of a gene occupying the same locus on a homologous chromosome. Since an individual can only carry two alleles for a given trait (one on each homologous chromosome),multiple alleles can only be observed at the population level. Therefore,they are always present at the same locus of the chromosome.

(A) The man has blood group $A$,so his genotype can be $I^AI^A$ or $I^AI^O$.
The woman has blood group $B$,so her genotype can be $I^BI^B$ or $I^BI^O$.
If we consider the heterozygous condition for both parents $(I^AI^O \times I^BI^O)$,the possible combinations for the offspring are:
$1. I^AI^B$ (Blood group $AB$)
$2. I^AI^O$ (Blood group $A$)
$3. I^BI^O$ (Blood group $B$)
$4. I^OI^O$ (Blood group $O$)
Therefore,all four blood groups ($A, B, AB,$ and $O$) are possible in their offspring.

(C) : The three alleles $I^A, I^B$ and $i$ of gene $I$ in the $ABO$ blood group system can produce six different genotypes and four different phenotypes as shown below:

Genotypes	Phenotypes
$I^AI^A, I^Ai$	Blood group $A$
$I^BI^B, I^Bi$	Blood group $B$
$I^AI^B$	Blood group $AB$
$ii$	Blood group $O$

Thus, there are four distinct phenotypes: $A, B, AB$ and $O$.

(C) : The three alleles $I^A$,$I^B$,and $i$ of gene $I$ in the $ABO$ blood group system can produce six different genotypes and four different phenotypes as shown below:

Genotypes	Phenotypes
$I^AI^A, I^Ai$	Blood group $A$
$I^BI^B, I^Bi$	Blood group $B$
$I^AI^B$	Blood group $AB$
$ii$	Blood group $O$

Thus,there are a total of four possible phenotypes: $A, B, AB,$ and $O$.

(B) The $ABO$ blood group system in humans is controlled by the gene $I$. The gene $I$ has three alleles: $I^A, I^B,$ and $i$.
Since there are three alleles,the possible genotypes are $I^A I^A, I^A i, I^B I^B, I^B i, I^A I^B,$ and $ii$,totaling $6$ genotypes.
However,the phenotypes are determined by the expression of these alleles. $I^A$ and $I^B$ are dominant over $i$,and $I^A$ and $I^B$ show codominance.
The resulting phenotypes are:
$1$. Type $A$ (from $I^A I^A$ or $I^A i$)
$2$. Type $B$ (from $I^B I^B$ or $I^B i$)
$3$. Type $AB$ (from $I^A I^B$)
$4$. Type $O$ (from $ii$)
Thus,there are $4$ distinct phenotypes.

(D) The mother has blood group $B$,which can have genotypes $I^B I^B$ or $I^B i$. The father has blood group $AB$,which has the genotype $I^A I^B$.
If the mother is $I^B I^B$,the possible offspring genotypes are $I^A I^B$ $(AB)$ and $I^B I^B$ $(B)$.
If the mother is $I^i I^B$,the possible offspring genotypes are $I^A I^B$ $(AB)$,$I^A i$ $(A)$,$I^B I^B$ $(B)$,and $I^B i$ $(B)$.
In both scenarios,the blood group $O$ $(ii)$ cannot be produced because the father does not carry the $i$ allele.

(C) The blood group of the child is $O$,which means the genotype of the child is $I^O I^O$.
This implies that the child must have inherited one $I^O$ allele from the mother and one $I^O$ allele from the father.
Since the father has blood group $B$,his possible genotypes are $I^B I^B$ (homozygous) or $I^B I^O$ (heterozygous).
Because the child inherited an $I^O$ allele from the father,the father must possess at least one $I^O$ allele.
Therefore,the genotype of the father must be $I^B I^O$.

(D) The $ABO$ blood group system in humans is controlled by the gene $I$. This gene has three alleles: $I^A$,$I^B$,and $i$.
Since there are more than two alleles present for a single gene locus within a population,this phenomenon is known as multiple alleles.
In this system,$I^A$ and $I^B$ are dominant over $i$,while $I^A$ and $I^B$ exhibit codominance when present together.

(D) The blood group of the mother is $O$,which means her genotype is $ii$.
The blood group of the father is $A$. The genotype of the father can be either $I^A I^A$ (homozygous) or $I^A i$ (heterozygous).
Case $1$: If the father is $I^A I^A$,the cross is $ii \times I^A I^A$,resulting in offspring with genotype $I^A i$ (Blood group $A$).
Case $2$: If the father is $I^A i$,the cross is $ii \times I^A i$,resulting in offspring with genotypes $I^A i$ (Blood group $A$) and $ii$ (Blood group $O$).
Therefore,the possible blood groups for the child are $A$ or $O$.

(C) The $ABO$ blood grouping in humans is controlled by the gene $I$.
This gene has three alleles: $I^A$,$I^B$,and $i$.
The alleles $I^A$ and $I^B$ produce slightly different forms of the sugar polymer that protrudes from the plasma membrane of red blood cells,while the allele $i$ does not produce any sugar.
Because humans are diploid organisms,each person possesses any two of the three $I$ gene alleles.

(D) Multiple allelism refers to the existence of more than two alleles for a single gene locus within a population.
In humans,the $ABO$ blood grouping system is a classic example of multiple allelism.
The gene $I$ controls the $ABO$ blood grouping,which has three alleles: $I^A$,$I^B$,and $i$.
Since there are three alleles,there are more than two possible phenotypes and genotypes in the population.

(A) Pseudoalleles are genes that are functionally related and are located very close to each other on the same chromosome. They appear to be alleles of the same gene because they occupy the same locus or closely linked loci and affect the same trait. Mutations occurring at these closely linked sites result in the formation of pseudoalleles.

(C) The $ABO$ blood group system in humans is an example of multiple allelism.
There are three alleles: $I^A, I^B,$ and $i$.
- $I^A$ and $I^B$ are codominant,while $i$ is recessive to both.
- The possible genotypes are: $I^A I^A, I^A i$ (Phenotype: $A$),$I^B I^B, I^B i$ (Phenotype: $B$),$I^A I^B$ (Phenotype: $AB$),and $ii$ (Phenotype: $O$).
- Thus,the possible phenotypes are $A, B, AB,$ and $O$,which totals to $4$ distinct phenotypes.

(C) To determine the possible genotypes and phenotypes of the children, we perform a Punnett square cross between the parents with genotypes $I^AI^B$ and $I^Ai$.
Parental gametes:
Parent $1$ $(I^AI^B)$: $I^A, I^B$
Parent $2$ $(I^Ai)$: $I^A, i$
Punnett Square:
- $I^A \times I^A = I^AI^A$ (Blood type $A$)
- $I^A \times i = I^Ai$ (Blood type $A$)
- $I^B \times I^A = I^AI^B$ (Blood type $AB$)
- $I^B \times i = I^Bi$ (Blood type $B$)
Possible Genotypes: $I^AI^A, I^Ai, I^AI^B, I^Bi$ (Total $4$ distinct genotypes).
Possible Phenotypes: Blood type $A$, Blood type $AB$, Blood type $B$ (Total $3$ distinct phenotypes).
Therefore, the correct answer is $4$ genotypes and $3$ phenotypes.

(A) The blood group $A$ can have genotypes $I^A I^A$ or $I^A i$. The blood group $B$ can have genotypes $I^B I^B$ or $I^B i$.
If the male is $I^A i$ and the female is $I^B I^B$,the possible offspring genotypes are $I^A I^B$ (blood group $AB$) and $I^B i$ (blood group $B$).
This matches the given progeny blood groups ($AB$ or $B$).
Therefore,the correct genotype for the parents is $I^A i$ (Male) and $I^B I^B$ (Female).

(N/A) The blood group characteristic in humans is controlled by three alleles,namely,$I^A$,$I^B$,and $i$. The alleles $I^A$ and $I^B$ are codominant,whereas allele $i$ is recessive to both. Individuals with genotypes $I^A I^A$ and $I^A i$ have blood group $A$,while individuals with genotypes $I^B I^B$ and $I^B i$ have blood group $B$. Persons with genotype $I^A I^B$ have blood group $AB$,and those with blood group $O$ have genotype $ii$.
Since the child has blood group $O$ (genotype $ii$),the child must have inherited one $i$ allele from each parent. Therefore,the parents must be heterozygous for their respective blood groups.
Father's genotype: $I^A i$ (Blood group $A$)
Mother's genotype: $I^B i$ (Blood group $B$)
When these parents are crossed:
Parents: $I^A i \times I^B i$
Gametes: $(I^A, i) \times (I^B, i)$
Possible genotypes of offspring:
$1$. $I^A I^B$ (Blood group $AB$)
$2$. $I^A i$ (Blood group $A$)
$3$. $I^B i$ (Blood group $B$)
$4$. $ii$ (Blood group $O$)
Thus,the other possible genotypes of the offspring are $I^A I^B$,$I^A i$,and $I^B i$.

(A) $ABO$ blood grouping provides a classic example of multiple alleles.
Multiple alleles refer to the existence of more than two alleles for a single gene within a population. While an individual can only possess two alleles at a time,the presence of three or more alleles can only be observed through population studies.
Occasionally,a single gene product may produce more than one effect. For example,starch synthesis in pea seeds is controlled by one gene with two alleles ($B$ and $b$). $BB$ homozygotes synthesize starch effectively,resulting in large starch grains. In contrast,$bb$ homozygotes have lower efficiency,producing smaller starch grains.
Upon maturation,$BB$ seeds appear round,and $bb$ seeds appear wrinkled. Heterozygotes $(Bb)$ produce round seeds,suggesting $B$ is the dominant allele. However,the starch grains in $Bb$ seeds are of intermediate size. If starch grain size is considered the phenotype,the alleles exhibit incomplete dominance.
Therefore,dominance is not an autonomous feature of a gene or its product. It depends on the gene product,the resulting phenotype,and the specific phenotype chosen for examination when a single gene influences multiple traits.

(B) In a diploid organism,every chromosome exists in a pair,known as homologous chromosomes.
Since a gene locus is located at a specific position on a chromosome,an individual can only carry a maximum of two alleles for a single gene—one on each homologous chromosome.
Multiple allelism is a phenomenon observed only at the population level,where more than two alternative forms of a gene exist within the gene pool of a species.

(N/A) Yes,a child can have blood group '$O$' if both parents are heterozygous for their respective blood groups.
Blood group inheritance is controlled by three alleles: $I^A$,$I^B$,and $i$.
- $A$ person with blood group '$A$' can have the genotype $I^A I^A$ (homozygous) or $I^A i$ (heterozygous).
- $A$ person with blood group '$B$' can have the genotype $I^B I^B$ (homozygous) or $I^B i$ (heterozygous).
If both parents are heterozygous,i.e.,the father has genotype $I^A i$ and the mother has genotype $I^B i$,the cross is as follows:
Parents: $I^A i \times I^B i$
Gametes: $(I^A, i) \times (I^B, i)$
Offspring genotypes: $I^A I^B$ $(AB)$,$I^A i$ $(A)$,$I^B i$ $(B)$,$ii$ $(O)$.
Thus,there is a $25\%$ probability that the child will have blood group '$O$' (genotype $ii$).

(D) The statement 'When $I^{A}$ and $I^{B}$ are present together,they express same type of sugar' is incorrect.
In the $ABO$ blood group system,the gene $I$ has three alleles: $I^{A}$,$I^{B}$,and $i$.
Alleles $I^{A}$ and $I^{B}$ produce different types of sugar polymers on the surface of red blood cells,while allele $i$ does not produce any sugar.
When both $I^{A}$ and $I^{B}$ are present together,they both express their own sugars simultaneously due to codominance,resulting in blood type $AB$. They do not express the same type of sugar.