Interaction of gene and cytoplasmic inheritance Questions in English

(A) Cytoplasmic inheritance (also known as extranuclear inheritance) refers to the transmission of genes located in cytoplasmic organelles such as mitochondria or chloroplasts.
Carl Correns was the scientist who first discovered cytoplasmic inheritance in $1909$ while working on the inheritance of leaf variegation in the plant $Mirabilis \, jalapa$ (Four O'clock plant).
He observed that the inheritance of leaf color was determined by the plastids present in the cytoplasm of the egg cell, rather than by nuclear genes following Mendelian patterns.

(B) Streptomycin is an aminoglycoside antibiotic that binds to the $30S$ ribosomal subunit of bacteria. In eukaryotic cells,it can interfere with the protein synthesis machinery of organelles like mitochondria and chloroplasts,which possess their own $DNA$ (cytoplasmic genes). By disrupting the translation process in these organelles,it can lead to mutations or the loss of cytoplasmic genetic information. Therefore,it is commonly used in research to induce mutations in cytoplasmic genes.

(B) : $A$ dominant epistatic allele suppresses the expression of a non-allelic gene, whether the latter is dominant or recessive.
The gene that suppresses the expression of a non-allelic gene is known as an epistatic gene.
The gene or locus that is suppressed by the presence of a non-allelic gene is termed as a hypostatic gene.
In summer squash or $Cucurbita \text{ } pepo$, there are three types of fruit colour: white, yellow, and green.
White colour is dominant over other colours, while yellow is dominant over green.
Yellow colour is formed only when the dominant epistatic gene is represented by its recessive allele $(w)$.
When the hypostatic gene is also recessive $(y)$, the colour of the fruit is green.
Thus, the inheritance pattern is:
$W-Y- \text{ or } W-yy \rightarrow \text{White}$
$wwY- \rightarrow \text{Yellow}$
$wwyy \rightarrow \text{Green}$

(A) Extranuclear inheritance,also known as cytoplasmic inheritance,refers to the transmission of genes located outside the nucleus,typically in mitochondria or chloroplasts,or through cytoplasmic particles.
In $Paramecium$,the presence of 'kappa particles' in the cytoplasm is a classic example of extranuclear inheritance.
These particles are responsible for the 'killer' trait,where individuals containing them can kill sensitive strains.
Color blindness,Phenylketonuria,and Tay-Sachs disease are all examples of nuclear (Mendelian) genetic disorders.

(A) Extranuclear inheritance,also known as cytoplasmic inheritance,refers to the transmission of genes that are located outside the nucleus.
In eukaryotic cells,the organelles that contain their own $DNA$ (extranuclear $DNA$) are the mitochondria and the chloroplasts.
These organelles possess their own genome,which is inherited independently of the nuclear chromosomes,typically through the cytoplasm of the egg cell.
Therefore,the presence of genes in mitochondria and chloroplasts is responsible for extranuclear inheritance.

(A) Epistasis is a genetic interaction where the expression of one gene is modified or masked by the presence of one or more other genes.
In this phenomenon,the gene that suppresses the effect of another gene is called the epistatic gene,and the gene whose effect is suppressed is called the hypostatic gene.
Unlike dominance,which involves the interaction between alleles of the same gene,epistasis involves the interaction between different gene loci.

(B) Cytoplasmic inheritance,also known as extranuclear inheritance,refers to the transmission of genes present in cytoplasmic organelles like mitochondria or chloroplasts.
Since the zygote receives the majority of its cytoplasm from the egg cell (ovum) during fertilization,traits controlled by these organellar genes are inherited exclusively from the female parent.
This phenomenon is also known as maternal inheritance.

(C) The phenomenon where a trait is inherited exclusively from the mother is known as cytoplasmic inheritance or maternal inheritance.
In plants,male sterility is often associated with genes located in the mitochondrial $DNA$.
This is known as Cytoplasmic Male Sterility $(CMS)$.
Since mitochondria are inherited through the egg cytoplasm during fertilization,the trait follows maternal inheritance patterns.
Therefore,the correct option is $C$.

(A) Complementary genes are two independent pairs of genes that interact to produce a single trait,where each gene is required for the expression of the other.
In the $F_2$ generation of a dihybrid cross involving complementary genes,the phenotypic ratio is modified from the standard $9 : 3 : 3 : 1$ to $9 : 7$.
This occurs because the presence of at least one dominant allele at both loci $(A-B-)$ results in one phenotype (ratio $9$),while any other combination (where one or both genes are homozygous recessive) results in the alternative phenotype (ratio $3+3+1 = 7$).

(D) Complementary genes are two non-allelic genes that interact to produce a specific phenotype, which neither gene can produce on its own. For example, in the sweet pea $(Lathyrus \, odoratus)$, the production of purple flower color requires the presence of two dominant genes ($C$ and $P$). If either gene is absent (e.g., $ccPP$ or $Ccpp$), the flower remains white. Thus, these genes complement each other to express the trait.

$(A)$ Extranuclear inheritance, also known as cytoplasmic inheritance, refers to the transmission of genes present in cytoplasmic organelles like mitochondria or chloroplasts, or other cytoplasmic factors.
In $Paramecium$, the 'killer' trait is determined by cytoplasmic particles called $\kappa$ particles.
These $\kappa$ particles contain $DNA$ and are capable of self-replication, which is a classic example of extranuclear or cytoplasmic inheritance.
Therefore, the correct option is $A$.

(D) Cytoplasmic male sterility $(CMS)$ is a condition in plants where the plant is unable to produce functional pollen.
This trait is inherited through the cytoplasm,specifically through the extranuclear $DNA$.
In most cases,the genes responsible for $CMS$ are located in the mitochondrial genome rather than the nuclear or chloroplast genome.
Therefore,the correct option is $D$.

(B) Mitochondrial $DNA$ is inherited exclusively through the cytoplasm of the egg cell (maternal inheritance).
Since the parent with the mitochondrial mutation is used as the male,the sperm contributes only nuclear $DNA$ and virtually no cytoplasm to the zygote.
Therefore,the mitochondrial mutation is not transmitted to the $F_1$ generation,and consequently,it will not be present in the $F_2$ generation.
Thus,the mutation is not observed in any offspring.

(A) Extranuclear inheritance,also known as cytoplasmic inheritance,refers to the transmission of genes that are located outside the nucleus.
In eukaryotic cells,organelles such as mitochondria and chloroplasts contain their own circular $DNA$,which is independent of the nuclear genome.
This $DNA$ is inherited through the cytoplasm,typically from the maternal parent,and is responsible for extranuclear inheritance.
Therefore,the correct option is $A$.

(B) Cytoplasmic inheritance (also known as extranuclear or organellar inheritance) is the transmission of genes located in the cytoplasm,specifically within organelles like mitochondria or chloroplasts.
In most sexually reproducing organisms,the zygote receives the vast majority of its cytoplasm from the egg cell (ovum),while the sperm contributes little to no cytoplasm.
Therefore,traits governed by genes in the mitochondria or chloroplasts are almost exclusively inherited from the mother to all her offspring,regardless of their sex.
This results in a strong maternal effect observed in the progeny.

(N/A) Complementary genes are two pairs of non-allelic dominant genes that interact to produce a single phenotypic trait. However,neither gene can produce the trait on its own; the presence of both dominant genes is required for the expression of the phenotype.

(N/A) Epistasis is a form of gene interaction where one non-allelic gene masks or suppresses the phenotypic expression of another non-allelic gene. The gene that suppresses the other is known as the epistatic gene,while the gene whose expression is masked is called the hypostatic gene. This interaction is a deviation from standard Mendelian inheritance patterns.

(D) $1$. In the pedigree,the trait is present in every generation,which suggests it is a dominant trait.
$2$. The trait is observed in both males and females.
$3$. $A$ key observation is that an affected father passes the trait to his daughters,and an affected mother passes it to all her children (both sons and daughters).
$4$. This pattern of inheritance,where the trait is passed from an affected mother to all her offspring,is characteristic of mitochondrial or maternal inheritance.

(C) In genetics,$Epistasis$ is a phenomenon where the effect of one gene is dependent on the presence of one or more 'modifier' genes.
$1$. The gene that suppresses or masks the expression of another gene is called the $Epistatic$ gene.
$2$. The gene whose expression is suppressed or masked by the epistatic gene is known as the $Hypostatic$ gene.
$3$. Since the question asks for the name of the gene whose expression is not occurring (the one being suppressed),the correct term is $Hypostatic$ gene.

(B) Dominance refers to the interaction between two alleles of the same gene,where one allele masks the expression of the other in a heterozygote.
Epistasis refers to the interaction between two or more different (non-allelic) genes,where one gene masks or modifies the phenotypic expression of another gene.
Therefore,the key difference is that dominance involves alleles of the same locus,whereas epistasis involves the interaction between different loci.

(D) Epistasis is a genetic interaction where one gene masks or interferes with the expression of another gene.
$1$. In poultry,the white plumage color is often due to a dominant epistatic gene $(I)$ that inhibits the expression of color genes.
$2$. In mice,coat color inheritance often involves epistatic interactions where one gene determines the presence of pigment and another determines the color.
$3$. In summer squash,fruit color inheritance (white,yellow,and green) is a classic example of dominant epistasis.
Since all these organisms exhibit various forms of epistasis,the correct answer is $D$.

(A) The collective term for all the cytoplasmic genes present in the cytoplasm of a cell is known as the $Plasmon$.
Cytoplasmic inheritance refers to the transmission of genes located in the cytoplasm (specifically in organelles like mitochondria and chloroplasts) rather than the nucleus.
These genes are collectively referred to as the $Plasmon$.

(B) Cytoplasmic inheritance,also known as extranuclear inheritance,refers to the transmission of genes located in organelles like mitochondria or chloroplasts.
In most sexually reproducing organisms,the zygote receives the majority of its cytoplasm from the egg cell (ovum),while the sperm contributes primarily its nucleus.
Therefore,cytoplasmic genes are inherited through the female parent (maternal inheritance).
Thus,the correct option is $B$.

(B) Cytoplasmic inheritance,also known as extranuclear inheritance,refers to the transmission of genes located in organelles like mitochondria or chloroplasts. In most organisms,these organelles are inherited from the mother through the egg cell,as the sperm contributes very little or no cytoplasm to the zygote. Therefore,cytoplasmic inheritance is commonly referred to as maternal inheritance. Since it is not passed through the father,it is not paternal inheritance.

(C) Cytoplasmic inheritance (also known as extranuclear inheritance) refers to the transmission of genes located outside the nucleus. In plants,these genes are primarily found in the $DNA$ of organelles such as mitochondria and chloroplasts. Since chloroplasts are the most prominent site for such inheritance in photosynthetic plants,option $C$ is the most appropriate answer.

(B) Cytoplasmic inheritance,also known as extranuclear inheritance,involves the transmission of genes located in organelles like mitochondria or chloroplasts. Since the zygote receives the majority of its cytoplasm from the egg cell (ovum) and very little or none from the sperm,the traits governed by these cytoplasmic genes are inherited exclusively from the mother. Therefore,cytoplasmic inheritance always shows maternal characters.

(D) $W. Bateson$ and $R. C. Punnett$ observed complementary gene interaction for flower colour in sweet pea $(Lathyrus \text{ } odoratus)$.
In complementary interaction, two separate pairs of genes interact to produce the phenotype in such a way that neither of the dominant genes is expressive unless the other one is present.
In $F_{2}$ generation, complementary genes produce a ratio of $9: 7$.

(A) Cytoplasmic male sterility $(CMS)$ is a condition in plants where the plant is unable to produce functional pollen.
This trait is inherited maternally because the genes responsible for $CMS$ are located in the mitochondrial genome.
Since mitochondria are inherited through the egg cytoplasm,the progeny exhibit the male sterile phenotype.
Therefore,the genes responsible for this phenomenon reside in the mitochondria.

(B) The cross is between $CcAa$ (agouti) and $ccAA$ (albino).
The gametes produced by $CcAa$ are $CA, Ca, cA, ca$.
The gametes produced by $ccAA$ are $cA$.
Performing the Punnett square cross:
$1$. $CA \times cA = CcAA$ (Agouti)
$2$. $Ca \times cA = CcAa$ (Agouti)
$3$. $cA \times cA = ccAA$ (Albino)
$4$. $ca \times cA = ccAa$ (Albino)
In the resulting progeny,there are $2$ albino mice ($ccAA$ and $ccAa$) out of $4$ total offspring. Therefore,the number of albino mice produced is $2$.

(C) Dominance is an interaction between two alleles of the same gene (intra-allelic or intragenic interaction),where one allele masks the expression of the other.
Epistasis is an interaction between two different genes where one gene masks or modifies the expression of another gene (intergenic or non-allelic interaction).
Therefore,epistasis is non-allelic (intergenic) and dominance is interallelic (intragenic).