Mendelism Questions in English

(A) Mendelism refers to the principles of inheritance formulated by Gregor Johann Mendel.
He was the first to conduct systematic experiments on pea plants and formulate clear-cut laws of heredity,which explain how traits are passed from parents to offspring.
Therefore,Mendelism is primarily related to the study of heredity in living beings.

(C) . Genetics is the branch of biology that deals with the study of heredity and the variations in organisms.

(C) The term 'genetics' was first proposed and used by William Bateson in $1905$ to describe the study of heredity and variation.

(B) Gregor Johann Mendel ($1822-1884$, Austria) is known as the father of genetics. He is considered the first geneticist because he was the first to demonstrate the mechanism of transmission of characters from one generation to the next through his experiments on pea plants.

(C) Gregor Mendel was born on July $20, 1822$, and passed away on January $6, 1884$.
Since the year $1822$ falls within the $19^{th}$ century (which spans from $1801$ to $1900$), the correct answer is $19^{th}$ century.

(D) Gregor Mendel was a native of Austria. He served as an abbot (head) of the Augustinian monastery of St. Thomas at Brunn,which was located in the Austrian Empire (now Brno,Czech Republic) in $1847$.

(C) Gregor Mendel was an Augustinian friar who performed his pioneering experiments on garden pea plants $(Pisum \text{ } sativum)$ in the garden of the St. Thomas's Abbey (a monastery) in Brünn, which was then part of the Austrian Empire (now Brno, Czech Republic). Therefore, the correct location is the Monastery of Brünn.

(A) Mendel proposed the term $Factor$ (or $determiner$) for the units of inheritance.
These factors are now known as $genes$ (a term coined by $Johannsen$ in $1905$).
Therefore,the correct option is $A$.

(A) The correct answer is $A$.
$Heredity$ is the process by which genetic characters are transmitted from parents to their offspring,resulting in the resemblance of individuals to their progenitors.

(C) The correct answer is $C$.
The checkerboard,commonly known as the $Punnett$ square,was developed by the British geneticist $R.C. Punnett$ in $1927$.
It is a graphical representation used to predict the probability of all possible genotypes and phenotypes of offspring resulting from a genetic cross between two organisms.

(A) Gregor Mendel's work remained unrecognized for many years until it was rediscovered in $1900$ $A.D.$
Three scientists,Hugo de Vries (Netherlands),Carl Correns (Germany),and Erich von Tschermak (Austria),independently conducted experiments and reached conclusions similar to Mendel's,thereby validating his principles of inheritance.

(D) In tomato plants $(Solanum \ lycopersicum)$,several traits follow Mendelian inheritance patterns.
$1$. Fruit color: Red fruit color is dominant over yellow fruit color.
$2$. Fruit shape: Rounded fruit shape is dominant over pear-shaped fruit.
$3$. Stem color: Violet (purple) stem color is dominant over green stem color.
Since all three traits listed are dominant characters in tomato plants,the correct answer is $D$.

(C) pure line refers to a population of individuals that are homozygous for a particular trait.
Because they are homozygous,they consistently produce offspring that exhibit the same phenotype and genotype as the parents,generation after generation.
Therefore,a pure line organism produces individuals of its own characters.

(A) The transmission of characters from parents to offspring is known as heredity or inheritance. When an offspring exhibits a character present in either of its parents,it indicates that the trait has been passed down through genetic material (genes) located on chromosomes. Therefore,such a character is defined as a hereditary character.

(A) Gregor Johann Mendel is known as the 'Father of Genetics'.
He conducted his hybridization experiments on the garden pea plant,scientifically known as $Pisum$ $sativum$.
He chose this plant because it has a short life cycle,produces many seeds,and exhibits several contrasting traits,which made it ideal for studying inheritance patterns over multiple generations.

(A) Gregor Johann Mendel conducted his hybridization experiments on the garden pea plant,scientifically known as $Pisum$ $sativum$. He chose this plant because it has several contrasting traits,a short life cycle,and is easy to cultivate,which allowed him to observe inheritance patterns over several generations.

(B) Gregor Johann Mendel's success in his experiments on pea plants was primarily due to his systematic approach.
He focused on studying one or two contrasting traits (characters) at a time,which allowed him to analyze the inheritance patterns clearly without confusion.
By keeping accurate records and using statistical analysis for the large number of offspring,he was able to derive the laws of inheritance.
Therefore,the study of one character at one time was a key factor in his success.

(B) Mendel chose pea plants $(Pisum \text{ } sativum)$ because they possessed several distinct, easily observable, and contrasting traits.
Specifically, he identified $7$ pairs of contrasting characters:
$(1)$ Stem height (tall/dwarf)
$(2)$ Flower position (axial/terminal)
$(3)$ Pod shape (inflated/constricted)
$(4)$ Pod colour (green/yellow)
$(5)$ Seed shape (round/wrinkled)
$(6)$ Seed colour (yellow/green)
$(7)$ Seed coat colour (coloured/white).

(D) Mendel chose $7$ pairs of contrasting characters in pea plants $(Pisum \text{ } sativum)$ for his experiments.
These characters are:
$1$. Stem height (Tall/Dwarf)
$2$. Flower colour (Violet/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)
Therefore, the correct option is $D$.

(B) Mendel studied seven pairs of contrasting traits in pea plants.
Later research revealed that the genes responsible for these seven traits are located on only four different pairs of chromosomes in the pea plant $(Pisum \text{ } sativum)$.
These chromosomes are chromosome numbers $1, 4, 5,$ and $7$.

(D) The term "genotype" was coined by the Danish botanist $W.L. Johanssen$ in $1909$.
It refers to the genetic constitution or the entire genetic makeup of an individual organism, which determines its hereditary characteristics.

(A) The genetic constitution or the genetic makeup of an organism is known as its $Genotype$.
$Phenotype$ refers to the observable physical or biochemical characteristics of an organism,as determined by both genetic makeup and environmental influences.
$Holotype$ is a term used in taxonomy to refer to a single physical specimen of an organism that was used when the species was formally described.

(D) The term 'Allelomorph' was proposed by William Bateson in $1902$.
It is used to describe alternative forms of a gene that occupy the same locus on a homologous chromosome.
The term 'Allele' is an abbreviated form of 'Allelomorph'.

(B) The term 'allelomorphic' (or allele) refers to alternative forms of a gene that occupy the same locus on homologous chromosomes. These forms control the same trait but result in different expressions,which are known as a pair of contrasting characters. For example,in pea plants,the gene for height has two alleles: one for tallness and one for dwarfness.

(C) dominant allele is defined as an allele that expresses its phenotype even in the presence of a recessive allele.
Therefore,it is expressed in both the homozygous condition (e.g.,$TT$) and the heterozygous condition (e.g.,$Tt$).
Conventionally,dominant alleles are represented by capital letters,such as $T$ for tallness in pea plants or $R$ for round seeds.

(B) The correct answer is $(b)$.
According to Mendel's Law of Dominance,when two homozygous individuals with contrasting traits are crossed,the trait that appears in the $F_1$ generation is called the dominant trait.
Since all $F_1$ plants have yellow seeds,the allele for yellow color expresses itself in the presence of the green allele,confirming that the yellow seed allele is dominant.

(A) An organism is said to be homozygous for a specific trait if it possesses two identical alleles for that trait (e.g.,$TT$ or $tt$).
Homozygous individuals are pure for the character and breed true,meaning they produce offspring with the same character upon self-fertilization.

(A) In $F_2$ generation,the dwarf trait is expressed only when the genotype is homozygous recessive $(tt)$.
According to Mendel's law of dominance,the factor that is unable to express its effect in the presence of its contrasting dominant factor in a heterozygote is called a recessive factor.
Since dwarfness is masked by tallness in the $F_1$ generation and only reappears in the $F_2$ generation in homozygous condition,it is considered a recessive trait.

(B) test cross is performed to determine the genotype of an organism showing a dominant phenotype. In this cross,the individual is crossed with a parent that is homozygous recessive for the trait. If the offspring show a $1:1$ ratio of dominant to recessive phenotypes,the individual is heterozygous. If all offspring show the dominant phenotype,the individual is homozygous dominant.

(A) In a genetic cross,the trait that appears in the majority of the offspring in the $F_1$ generation is considered the dominant trait. Since the red flower colour appears more frequently than the white flower colour,the red colour is the dominant character,while the white colour is the recessive character.

(A) In $Pisum \text{ } sativum$ (pea plant), Mendel identified seven pairs of contrasting traits.
For the pod colour trait, green pod colour is the dominant character, while yellow pod colour is the recessive character.
Therefore, the green colour of the pod is a dominant trait.

(D) According to Mendel's experiments on pea plants $(Pisum \text{ } sativum)$, the dominant traits include tall stem, axial flower position, green pod colour, inflated pod shape, yellow seed colour, round seed shape, and grey seed coat.
In option $(D)$, green coloured pod and rounded seed are both dominant characters.
In option $(A)$, dwarf plant is recessive.
In option $(B)$, terminal fruit (flower) and wrinkled seed are both recessive.
In option $(C)$, white testa (seed coat) is recessive.

(B) In $Mendelian$ genetics,$Gregor$ $Mendel$ identified seven pairs of contrasting traits in pea plants. For the pod shape,the $Inflated$ shape is the dominant trait,while the $Constricted$ shape is the recessive trait. Therefore,option $(b)$ is the correct answer.

(C) In $Mendelian$ genetics,the flower color in pea plants is determined by specific alleles. The white flower color is a recessive trait. According to the law of segregation,a plant will always produce white flowers if it is homozygous recessive for the flower color gene (genotype $ww$). The presence of a white seed coat is often correlated with white flowers because both traits are linked to the same genetic background in many pea varieties (specifically,the $A$ gene locus). Therefore,a plant with a white seed coat is homozygous recessive for the flower color trait and will always produce white flowers.

(C) In genetics,the observable physical or biochemical characteristics of an organism,as determined by both genetic makeup and environmental influences,are called phenotypes.
Gregor Mendel studied seven pairs of contrasting traits in pea plants,such as stem height (tall/dwarf),flower colour (violet/white),and seed coat colour (grey/white).
Since these traits represent the physical appearance or observable characteristics of the plant,they are classified as phenotypes.

(B) Mendel selected $7$ pairs of contrasting characters in the garden pea $(Pisum \text{ } sativum)$.
These characters were: stem height, flower colour, flower position, pod shape, pod colour, seed shape, and seed colour.
Among the given options, plant colour (specifically flower colour was considered, but plant colour as a whole was not a specific trait) was not one of the $7$ pairs of contrasting characters he studied.
Therefore, the correct option is $B$.

(B) Mendel's Law of Independent Assortment states that the alleles of two (or more) different genes get sorted into gametes independently of one another.
Linkage refers to the physical association of genes on the same chromosome,which causes them to be inherited together,thereby violating the Law of Independent Assortment.
Since Mendel chose traits that were either on different chromosomes or far apart on the same chromosome,he observed independent assortment and did not encounter the phenomenon of linkage.

(B) Mendel's laws of inheritance,specifically the Law of Segregation and the Law of Independent Assortment,are based on the behavior of chromosomes during cell division.
Meiosis is the specialized type of cell division that reduces the chromosome number by half,leading to the formation of gametes.
During meiosis,homologous chromosomes segregate into different gametes,which provides the physical basis for Mendel's Law of Segregation.
Furthermore,the independent alignment of different pairs of homologous chromosomes during metaphase $I$ explains the Law of Independent Assortment.
Therefore,meiosis is the process that explains the transmission of genetic material from parents to offspring according to Mendelian principles.

(C) reciprocal cross is a breeding experiment designed to test the role of parental sex on a given inheritance pattern. In this process,two crosses are performed: in the first cross,a male of strain $A$ is crossed with a female of strain $B$,and in the second cross,a female of strain $A$ is crossed with a male of strain $B$. This reversal of parental sexes helps determine if a trait is sex-linked or autosomal.

(C) Test cross: $A$ test cross is performed to determine the genotype of an individual showing a dominant phenotype.
In this cross,the individual is crossed with a homozygous recessive parent.
If the offspring show a $1:1$ phenotypic ratio,the individual is heterozygous.
If all offspring show the dominant trait,the individual is homozygous dominant.

(C) cross between an organism with an unknown genotype (or a heterozygous individual) and a homozygous recessive parent is known as a test cross.
In this cross,the $F_1$ hybrid (heterozygous,$Tt$) is crossed with a homozygous recessive parent $(tt)$.
The purpose of a test cross is to determine the genotype of an organism showing a dominant phenotype.
The resulting offspring ratio in a monohybrid test cross is $1:1$ (heterozygous $Tt$ : homozygous recessive $tt$).

(B) cross between an $F_1$ hybrid and its recessive parent is specifically known as a $Test \ cross$.
This type of cross is used to determine the genotype of an organism showing a dominant phenotype.
If the offspring show a $1:1$ phenotypic ratio,the parent was heterozygous.
If all offspring show the dominant trait,the parent was homozygous dominant.

(C) cross between an $F_1$ hybrid and one of its parents is called a back cross. This technique is frequently used in plant breeding to improve the traits of a specific parent by repeatedly crossing the offspring with that parent.

(B) back cross is a cross between an $F_1$ hybrid and either of its parents. $A$ test cross is a specific type of back cross where an $F_1$ hybrid is crossed with the recessive parent only. Therefore,every test cross is a back cross,but not every back cross is a test cross.

(D) When an $F_1$ hybrid (heterozygous, $Tt$) is crossed with a homozygous dominant parent $(TT)$, this is known as a backcross.
The cross is represented as: $Tt \times TT$.

Gametes	$T$	$T$
$T$	$TT$	$TT$
$t$	$Tt$	$Tt$

As shown in the table, all offspring are phenotypically dominant ($TT$ and $Tt$). Therefore, no recessive offspring are produced.

(B) According to Mendel's law of dominance,when a pure dominant trait is crossed with a pure recessive trait,the $F_1$ generation expresses only the dominant trait.
Here,the red flower color $(R)$ is dominant over the white flower color $(r)$.
When a pure red-flowered plant $(RR)$ is crossed with a pure white-flowered plant $(rr)$,all offspring in the $F_1$ generation will have the genotype $Rr$.
Since $R$ is dominant,all $F_1$ plants will be red-flowered.
$\mathop {RR}\limits_{\text{(Pure Red)}} \times \mathop {rr}\limits_{\text{(Pure White)}} \xrightarrow{} Rr \text{ (All Red-flowered plants)}$

(A) The total number of plants produced is $140 + 40 = 180$.
Since both tall and dwarf plants are produced from the same parent,the parent must be heterozygous $(Tt)$.
When a heterozygous plant $(Tt)$ is self-pollinated,the offspring genotypes follow the Mendelian ratio of $1:2:1$ for $TT:Tt:tt$.
$TT$ represents homozygous tall plants,$Tt$ represents heterozygous tall plants,and $tt$ represents homozygous dwarf plants.
Therefore,the offspring will consist of all three genotypes: $TT, Tt$,and $tt$.

(D) This is a test cross where a hybrid individual $(Bb)$ is crossed with a homozygous recessive individual $(bb)$.
According to Mendelian genetics,the cross $Bb \times bb$ results in a $1:1$ phenotypic ratio of black $(Bb)$ and brown $(bb)$ offspring.
Since there are $24$ offspring in total,we expect approximately $12$ black and $12$ brown mice.
Furthermore,the inheritance of coat color is independent of sex,meaning the distribution of males and females should be approximately equal within each phenotypic group.
Option $(d)$ shows $12$ black mice $(5$ males $+ 7$ females$)$ and $12$ brown mice $(6$ males $+ 6$ females$)$,which perfectly matches the expected $1:1$ ratio for both phenotype and sex.

(D) In mice,black coat color $(B)$ is dominant over brown coat color $(b)$. $A$ pure black mouse has the genotype $BB$,while a hybrid black mouse has the genotype $Bb$. To determine if a black mouse is pure $(BB)$ or hybrid $(Bb)$,we perform a test cross with a recessive individual (brown mouse,$bb$).
$1$. If the black mouse is pure $(BB)$,the cross $BB \times bb$ will result in all offspring being black $(Bb)$.
$2$. If the black mouse is hybrid $(Bb)$,the cross $Bb \times bb$ will result in a $1:1$ ratio of black $(Bb)$ and brown $(bb)$ offspring.
Therefore,crossing it with a brown mouse is the standard method to identify the genotype.

(A) The cross between blue-flowered and white-flowered plants resulting in a $60:40$ ratio (approximately $1:1$) indicates a test cross between a heterozygous dominant $(Ww)$ and a homozygous recessive $(ww)$ parent.
Thus,the blue-flowered progeny are all heterozygous $(Ww)$.
When these blue-flowered $(Ww)$ plants are self-pollinated,the cross is $Ww \times Ww$.
According to Mendelian inheritance,the phenotypic ratio of the offspring will be $3$ blue-flowered $(WW, Ww, Ww)$ to $1$ white-flowered $(ww)$.
This $3:1$ ratio corresponds to $75\%$ blue and $25\%$ white,which is approximately $76:24$.