Set : S&T : Genes : CIVIL SERVICES (PRELIMS), 2026
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Topic : Genes (for G S
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TOPIC : GENES (with questions
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UPSC(CSE)(Prelims) Exams.
MULTIPLE CHOICE QUESTIONS ON CONSTITUTION OF iNDIA
TOPIC : RIGHT TO LIFE
Question : Write short note on 'Mendelian and non-Mendelian traits'. (UPSC CSE (Mains)Exam 2025 Optional Paper-1 : Anthropology
Ans :
Categorising patterns of inheritance as Mendelian and non-Mendelian should be based on genotypic ratios, not phenotypic ratios, in offspring.
1)Genotypic ratios reflect the segregation and independent assortment of
alleles during Meiosis in parents , which are the underpinning of Mendel's Laws.
2)Phenotypic ratios reflect the modes of action of the gene products and the relationship between alleles in offspring.
Mendel developed the principles of segregation, independent assortment, and dominance based on his studies of 7 traits in peas, including flower colour, pea colour , and pear shape
Some examples of non-Mendelian inheritance :
1)Genes that reside in the genomes of mitochondria and chloroplasts display non-Mendelian inheritance.
2)Organelle transmission does not follow Mendel's Laws, the genes in organelles do not display Mendelian inheritance.
3)Epigenetic inheritance provides another example of non-Mendelian inheritance.
The Basis of Non-Mendelian Heredity: -
Non-Mendelian heredity is a term used to describe inheritance patterns that do not fit the classical Mendelian inheritance model, which allows breeders to create new varieties of plants with desired characteristics in a different way.
1)What are the advantages of selection pea by Gregor Mendel ? Ans :
========================================= Gregor Mendel:-
Mendel discovered that by crossing white flower and purple flower plants, the result was not a hybrid offspring.
Rather than being a mix of the two, the offspring was purple flowered. He then conceived the idea of heredity units, which he called "factors", one which is a recessive characteristic and the other dominant.
Mendel said that factors, later called genes, normally occur in pairs in ordinary
body cells, yet segregate during the formation of sex cells. Each member of the pair becomes part of the separate sex cell.
The dominant gene, such as the purple flower in Mendel's plants, will hide the recessive gene, the white flower. After Mendel self-fertilized the F1 generation and obtained the 3:1 ratio, he correctly theorized that genes can be paired in
three different ways for each trait; AA, aa, and Aa. The capital A represents the dominant factor and lowercase a represents the recessive.
Mendel stated that each individual has two factors for each trait, one from each parent. The two factors may or may not contain the same information. If the two factors are identical, the individual is called homozygous for the trait. If the two factors have different information, the individual is called heterozygous. The alternative forms of a factor are called alleles.
The genotype of an individual is made up of the many alleles it possesses. An individual's physical appearance, or phenotype, is determined by its alleles as well as by its environment. An individual possesses two alleles for each trait; one allele is given by the female parent and the other by the male parent. They are passed on when an individual matures and produces gametes: egg and sperm.
When gametes form, the paired alleles separate randomly so that each gamete receives a copy of one of the two alleles. The presence of an allele doesn't promise that the trait will be expressed in the individual that possesses it. In heterozygous individuals the only allele that is expressed is the dominant. The recessive allele is present but its expression is hidden.
Mendel summarized his findings in two laws:-
1)the Law of Segregation and
2)the Law of Independent Assortment.
Law of Segregation (The "First Law"):-
The Law of Segregation states that when any individual produces gametes, the copies of a gene separate, so that each gamete receives only one copy. A gamete will receive one allele or the other. The direct proof of this was later
found when the process of meiosis came to be known. In meiosis the paternal and maternal chromosomes get separated and the alleles with the characters are segregated into two different gametes.
Law of Independent Assortment (The "Second Law")
The Law of Independent Assortment, also known as "Inheritance Law", states that alleles of different genes assort independently of one another during gamete formation. While Mendel's experiments with mixing one trait always resulted in a 3:1 ratio between dominant and recessive phenotypes, his experiments with mixing two traits (dihybrid cross) showed 9:3:3:1 ratios. But the 9:3:3:1 table shows that each of the two genes are independently inherited with a 3:1 ratio. Mendel concluded that different traits are inherited independently of each other, so that there is no relation, for example, between a cat's color and tail length. This is actually only true for genes that are not linked to each other.
Independent assortment occurs during meiosis I in eukaryotic organisms, specifically metaphase I of meiosis, to produce a gamete with a mixture of the organism's maternal and paternal chromosomes. Along with chromosomal crossover, this process aids in increasing genetic diversity by producing novel genetic combinations.
In independent assortment the chromosomes that end up in a newly-formed gamete are randomly sorted from all possible combinations of maternal and paternal chromosomes. Because gametes end up with a random mix instead of a pre-defined "set" from either parent, gametes are therefore considered assorted independently. As such, the gamete can end up with any combination of paternal or maternal chromosomes. Any of the possible combinations of gametes formed from maternal and paternal chromosomes will occur with equal frequency. For human gametes, with 23 pairs of chromosomes, the number of possibilities is 2^23 or 8,388,608 possible combinations. The gametes will normally end up with 23 chromosomes, but the origin of any particular one will be randomly selected from paternal or maternal chromosomes. This contributes to the genetic variability of progeny.
1)What is Genetics ?
Ans : Genetics is a branch of biology which deals with principles of inheritance and its practices.
2)Progeny resembling the parents in morphological and physiological features has attracted the attention of many biologists. Who is the first to study this phenomenon systematically. ?
Ans : Gregor Mendel
3)Gregor Mendel studies which plants ?
Ans : Pea plants.
4)Who proposed the principles of inheritance , which are today referred as ‘Mendel’s Laws of Inheritence’ ?
Ans : While studying the pattern of inheritance in pea plants of contrasting characters, Mendel proposed the principles of inheritance, which are today referred to as ‘Mendel’s Laws of Inheritance’.
5) What Mendel proposed ?
Ans : He proposed that the ‘factors’ (later named as ‘genes’) regulating the characters are found in pairs known as alleles.
6)Which of the following are correct about observations of Gregor Mendel ?
a)He observed that the expression of the characters in the offspring follow a definite pattern in different–first generations (F1 ), second (F2 ) and so on. b)Some characters are dominant over others. The dominant characters are expressed when factors are in heterozygous condition (Law of Dominance). c)The recessive characters are only expressed in homozygous conditions. The characters never blend in heterozygous condition. A recessive character that was not expressed in heterozygous conditon may be expressed again when it becomes homozygous. Hence, characters segregate while formation of gametes
(Law of Segregation)
d)All the above
Ans: d
7)What is ‘genotype’
Ans : The factors (now known as ‘gene’) on chromosomes regulating the characters are called the ‘genotype’.
8)What is ‘phenotype’ ?
Ans : Physical expression of the characters is called ‘phenotype’
9) After knowing that the genes are located on the chromosomes, a good correlation was drawn between Mendel’s laws : segregation and assortment of chromosomes during meiosis
10)Many genes were linked to sexes also, and called as sex-linked genes. The two sexes (male and female) were found to have a set of chromosomes which were common, and another set which was different.
What are sex chromosomes ?
Ans : The chromosomes which were different in two sexes were named as sex chromosomes.
11)What are ‘autosomes’ ?
Ans : The remaining set was named as autosomes. (i.e.,other than sex chromosomes are called autosomes)
12)In human, a normal female has how many autosomes and how many sex chromosomes ?
Ans : In humans, a normal female has 22 pairs of autosomes and a pair of sex chromosomes (XX).
13)A male has how many pairs of autosomes and how many pairs of sex chromosomes ? Ans : A male has 22 pairs of autosomes and a pair of sex chromosome as XY.
14)In chicken which are sex chromosomes ?
Ans : In chicken, sex chromosomes in male are ZZ, and in females are ZW
15)What is ‘mutation’ in genetics ?
Ans : Mutation is defined as change in the genetic material.
A point mutation is a change of a single base pair in DNA.
16)What is the cause for Sickle-cell anemia ?
Ans : Sickle-cell anemia is caused due to change of one base in the gene coding for
beta-chain of hemoglobin.
17)How a ‘pedigree is useful ?
Ans : Inheritable mutations can be studied by generating a pedigree of a family.
18)What is ‘polyploidy’ ? What is ‘aneuploidy?
Ans : Some mutations involve changes in whole set of chromosomes (polyploidy) or change in a subset of chromosome number (aneuploidy).
This helped in understanding the mutational basis of genetic disorders.
19)What is the reason for Down’s syndrome ?
Ans : Down’s syndrome is due to trisomy of chromosome 21, where there is an extra copy of chromosome 21 and consequently the total number of chromosome becomes 47.
20)What is the reason for Turner’s syndrome ?
Ans : In Turner’s syndrome, one X chromosome is missing and the sex chromosome is as XO,
21)What is reason for Klineferlter’s syndrome ?
Ans : In Klinefelter’s syndrome, the condition is XXY. These can be easily studied by analysis of Karyotypes.
22)Who described Down’s syndrome ?
Ans : This disorder was first described by Langdon Down (1866)
23)What are the features of Down’s syndrome ?
Ans : The affected individual is short statured with small round head, furrowed tongue and partially open mouth . Palm is broad with characteristic palm crease. Physical, psychomotor and mental development is retarded.
24) Which are common examples of chromosomal disorders ?
Ans :
1)Down’s syndrome,
2)Turner’s syndrome,
3)Klinefelter’s syndrome are common examples of chromosomal disorders.
25)Which of the following are the correct characters’ of Down’s Syndrome’ ?
Ans : : The cause of this genetic disorder is the presence of an additional copy of the chromosome number 21 (trisomy of 21).
This disorder was first described by Langdon Down (1866). The affected individual is short statured with small round head, furrowed tongue and partially open mouth . Palm is broad with characteristic palm crease. Physical, psychomotor and mental development is retarded.
26) What is Klinefelter’s Syndrome ?
Ans : Klinefelter’s Syndrome : This genetic disorder is also caused due to the presence of an additional copy of Xchromosome resulting into a karyotype of 47, XXY. Such an individual has overall masculine development, however, the feminine development (development of breast, i.e., Gynaecomastia) is also expressed (Figure 4.17 a). Such individuals are sterile.
27)What is Turner’s syndrome ?
Ans : Turner’s Syndrome : Such a disorder is caused due to the absence of one of the X chromosomes, i.e., 45 with X0, Such females are sterile as ovaries are rudimentary besides other features including lack of other secondary sexual characters
28) What is pedigree analysis? Suggest how such an analysis can be useful?
Solution: Pedigree analysis is the study of family history over generations to trace the inheritance of specific traits.
It is useful in:-
i) Identifying genetic disorders and understanding inheritance atterns.
ii)Helping genetic counselors assess the risk of genetic diseases.
iii)Understanding how certain traits are passed through families.
29)Briefly mention the contribution of T.H. Morgan to genetics?
Solution: T.H. Morgan made several important contributions, including:-
● Proving that genes are located on chromosomes.
● Discovering sex-linked inheritance.
● Studying gene linkage and recombination.
● Developing the concept of chromosome mapping.
30) What is Dominance and Recessive ?
Ans:
Dominance: A dominant allele expresses itself in the presence of a recessive allele.
Recessive: A recessive allele only expresses itself in the absence of a dominant allele.
31)What is Homozygous and Heterozygous?
Ans :
Homozygous: An individual has two identical alleles for a trait (e.g., TT or tt).
Heterozygous: An individual has two different alleles for a trait (e.g., Tt)
32) What is Monohybrid and Dihybrid?
Ans :
Monohybrid: A cross between two organisms differing in a single trait (e.g., seed color).
Dihybrid: A cross between two organisms differing in two traits (e.g., seed color and seed shape)
33) Mention the advantages of selecting a pea plant for the experiment by Mendel?
Solution: Mendel chose pea plants for his experiments because:
● Pea plants show clear, contrasting traits (e.g., tall vs. short, round vs. wrinkled seeds, yellow vs. green pods), making it easier to study inheritance patterns.
● Pea plants have bisexual flowers, allowing for self-pollination, which helps in controlling the genetic cross.
● Cross-pollination can be easily controlled through emasculation. ● They have a short life cycle, producing many seeds quickly, which facilitates the study of multiple generations.
34)What is Co-dominance?
Ans : Co-dominance refers to the situation where both alleles in a heterozygote are fully expressed, neither being dominant over the other. Both alleles contribute equally to the phenotype.
Example: In human blood groups, the A and B alleles are co-dominant. If a person inherits the A allele from one parent and the B allele from the other, the result is AB blood type, where both A and B antigens are expressed on the surface of red blood cells.
35)What is Incomplete dominance?
Incomplete dominance is the phenomenon where neither allele is completely dominant over the other, leading to a blending of traits in the heterozygote. In the F1 generation, the resulting phenotype is an intermediate expression of the two parental traits.
Example: In Mirabilis jalapa (four o'clock plant), when a red-flowered plant is
crossed with a white-flowered plant, the F1 hybrid produces pink flowers, which is a blend of the red and white traits, demonstrating incomplete dominance.
36)What is point mutation? Give one example.
Solution: Point mutation refers to a genetic mutation where there is a change in a single nucleotide base pair in the DNA sequence. This can occur due to a substitution, insertion, or deletion of a single base pair, leading to a change in the codon, which may result in a change in the protein produced. Point mutations can sometimes cause significant effects, especially if they occur in crucial regions of the gene.
Example: Sickle Cell Anaemia
Sickle cell anaemia is caused by a point mutation where a single nitrogen base, guanine, is replaced by adenine at the sixth codon of the β-globin gene. This substitution causes the amino acid glutamic acid to be replaced by valine in the hemoglobin protein. This slight change leads to the formation of sickle-shaped red blood cells instead of the normal biconcave discs. The sickle-shaped cells are less flexible and can obstruct blood flow, causing the symptoms of sickle cell anaemia, such as pain and organ damage.
37)Who proposed the chromosomal theory of inheritance?
Solution: The chromosome theory of inheritance was proposed by Walter Sutton and Theodor Boveri in the early 20th century. They suggested that chromosomes, which carry genes, are the vehicles of inheritance and that the segregation and independent assortment of chromosomes during meiosis explain the inheritance patterns observed by Gregor Mendel.
38)Mention any two autosomal genetic disorders with their symptoms.
Solution: Autosomal Genetic Disorders and Their Symptoms
1)Down's Syndrome Symptoms :
● Flat hands and short neck
● Broad forehead
● Partially open mouth with a furrowed tongue
● Mongolian-type eyelid fold and stubby fingers
● Stunted psychomotor, physical, and mental development ● Heart deformities and deformities in other organs
● Underdeveloped genitalia and gonads
2)Sickle Cell Anaemia Symptoms :
● The shape of red blood cells (RBCs) changes from round, biconcave discs to sickle-shaped (curved) under low oxygen tension.
● Sickle-shaped RBCs are rigid and less flexible, causing them to get stuck in small blood vessels, which can lead to pain episodes, anemia, and organ damage.
● Individuals may experience episodes of severe pain, known as "sickle cell crises."
● Increased risk of infections, fatigue, and delayed growth.
39)What is the mode of inheritance of traits causing haemophilia? Ans: X-linked recessive transmission
====================================
MITOSIS :
40)In multicellular organisms , body growth is by ___________ division of cells . Ans : Mitotic / mitosis
41) For replacement of worn out tissues/cells (e.g. blood cells, skin cells) and repair of the injured tissues is by ___________ .
Ans : mitoses
42)Uncontrolled cell division (mitosis) in certain tissues/organs (cancer) results in ________ .
Ans : tumours
43) In Mitosis , cell division,how many daughter cells are formed ? Ans : Two
44)________ is the process in which the chromosomes of a nucleus undergo longitudinal duplication and their split halves migrate to the poles to constitute two daughter nuclei, identical to each other and also to the parent nucleus.
Ans : Mitosis
45) Mitosis is also known as _______ , as the number ofr chromosomes in the
parent cell and the daughter cells is the same .
Ans : equational division
======================================
MEIOSIS :
Meiosis is a type of cell division where the number of chromosomes is reduced to half in the daughter cells, hence it is also known as reduction division .
46)Which type of cell division is known as ‘reduction division’ ? Ans : Meiosis
47)In which type of cell division, the number of chromosomes is reduced to half in the daughnter cells ?
Ans : Meiosis
48) In Meiosis cell division , how many daughter cells are produced ? Ans : Four
49)Why the Meiosis cell division is called as reduction division ? Ans : The number of chromosomes is reduced to half.
50)Where the Meiosis cell division takes place ?
Ans : Meiosis occurs during different stages in the life cycle of different organisms in the body.
51)The crossing over results in variation of genetic characters in the offspring; variation form the raw material material for evolution. Happens in which stage ?
Ans : Meiosis II ( i.e., Cytokinesis)
52)What is the average cell cycle span for a mammalian cell ?
Ans : 24 Hours
53)Which part of the human body should one use to demonstrate stages of Mitosis ? Ans : Bone marrow
54)It is observed that heart cells do not exhibit cell division. Such cells do not divide further and exit G1 phase (Gap-1 phase) to enter an inactive stage, called _______ of cell cycle.
Ans : Go Phase
54)What is ‘Interphase’ in the phases of cell cycle ?
Ans : Interphase is the most active stage in the cell cycle , when the cell prepares for the division phase.
It consists of three sub-stages : -
i)G1 phase or Gap-2 phase: It corresponds to the interval between Mitosis (M-phase) and initiation of replication of DNA; the cell grows in size
ii)S Phase or Synthetic phase : It is the period during which DNA replication takes place and the amount of nucleic acid doubles.
iii)G2 phase or Gap-2 Phase : During this phase, more RNAs and proteins are synthesised in preparation for Mitosis and also for the growth of cells.
Note: Go - phase: Dedifferentiation
============================================ 55)What is Go (quiescent phase) of cell cycle ?
Ans : Go (Quiscent phase) represents an inactive stage in the cell cycle, where cells are metabolically active but do not undergo division, unless it becomes necessary to replace the worn out or injured cells. (Example : Heat cells )
=============================================
56)Question: List the main differences between Mitosis and Meiosis ?
Ans:
=============================================================== Genetic diseases :
57) Which of the following is correct about Down’s Syndrome ?
a)It is also called Trisomy 21
b)47 chromosomes in a cell instead of 46 chromosomes
c)Mental retardation , abnormal pattern of palm creases, flat face, sparse, straight hair and short stature ; Risk of cardiac anomalies, leukaemia, cataract, digestive blockages, lesser life expectancy . Down’s syndrome common in children born to old aged women (mmore than 40 years age)
d) All the above
Ans: d
Explanation : It is one of the Autosomal Genetic Disorders and Their Symptoms.
Down's Syndrome Symptoms :
a)Flat hands and short neck
b)Broad forehead
c)Partially open mouth with a furrowed tongue
d)Mongolian-type eyelid fold and stubby fingers
e)Stunted psychomotor, physical, and mental development
f)Heart deformities and deformities in other organs
g)Underdeveloped genitalia and gonads
58)Which of the following is correct about Turner syndrome ?
a)Sexually underdeveloped, short stature, folds of skin on the back of neck b)wide nipples, narrow aorta
c)pigmented moles, malformed elbows , infertile, normal intelligence d)All the above
Ans : d
59) Which of the following is correct about Klinifelter’s syndrome (XXY) ? a) Males have two or more X chromosomes instead of one
b)Reduced sexual maturity and secondary sexual characteristics c)breast swelling back of sperm formation. Slow learning or mental retardation d)All the above
Ans : d
60) Which of the following is correct about Jacob’s syndrome (XYY) ? a)Males have 2 T chromosomes
b)They are tall, have acne,
c)Speech and reading problems
d)All the above
Ans : d
61)Which of the following is correct about Cri-du-chat ?
a)Deletion of a portion of chromosome
b)mentally retarded
c)infants’ cry sounds like cat
d)All the above
Ans : d
62) “What could be the reason for Tay Sachs ?
Ans : Single defective enzyme which normally digests the fatty material. 63)Which of the following is correct about Phenylketonuria (PKU) ?
a)Recessive or genetic diseases lack of ability to breakdown the amino acid phenylanine in blood affects the development of nervous system.
b)Children should be on phenylalanine restricted diet throughout life c)Both (a) & (b)
d) None of these
Ans : c
64) Which of the following is correct about sickle cell anaemia ?
a)Abnormality in the amino acid sequence in haemoglobin
b)At the time of low oxygen concentration , the haemoglobin moles stick together to form long rods which stick together
c)The breakdown of the cells may result in clogging of blood vessels causing pain, poor circulation, jaundice, anaemia, internal haemorrhage, low resistance, damage to internal organs.
d)All the above
Ans : d
Explanation : Autosomal Genetic Disorders and Their Symptoms:
Sickle cell anaemia is caused by a point mutation where a single nitrogen base, guanine, is replaced by adenine at the sixth codon of the β-globin gene. This substitution causes the amino acid glutamic acid to be replaced by valine in the hemoglobin protein. This slight change leads to the formation of sickle-shaped red blood cells instead of the normal biconcave discs. The sickle-shaped cells are less flexible and can obstruct blood flow, causing the symptoms of sickle cell anaemia, such as pain and organ damage
● The shape of red blood cells (RBCs) changes from round, biconcave discs to sickle-shaped (curved) under low oxygen tension. ● Sickle-shaped RBCs are rigid and less flexible, causing them to get stuck in small blood vessels, which can lead to pain episodes, anemia, and organ damage.
● Individuals may experience episodes of severe pain, known as "sickle cell crises."
● Increased risk of infections, fatigue, and delayed growth.
65)Which of the following is correct about Hemochromatosis ?
a)This disease causes absorption of more iron from food than normal b)high iron content results in organ damage
c)Joint pain, fatigue and abdominal pain are the symptoms
d)All the above
Ans : d
66)Which of the following is correct about Neurofibromatosis (NF)?
a)The presence of a gene on chromosome 17 may cause the formation of benign tumours on the nerve cells
b)This may result in learning disabilities and hyperactivity
c)Both (a) and (b)
d) None of these
Ans : c
67) Which of the following is correct about Huntington’s disease ? a)Slow degeneration of brain cells produces jerking muscles, slurred speech
b)swallowing discomfort , loss of balance, mood swings, reasoning and memory loss, incapacitation.
c)This is due to the repeated DNA sequence
d)All the above
Ans : d
68)Which of the following is correct about colour blindness ?
a)X linked gene (green insensitive in females)
b)X linked gene causes red insensitivity in males
c)Both (a) & (b)
d)None of these
Ans : c
69)Which of the following is correct about Hemophilia ?
a)Lack of a clotting factor in the blood
b)Absence of clotting results in the excessive bleeding even from minor cuts c)Both (a) and ( b)
d) None of these
Ans : c
================================================= 70)How is sex determined in human beings?
a)Humans have an XX/XY sex determination pattern.
b)Female sex chromosomes are XX, while male sex chromosomes are XY.
c)Females can only generate gametes with X chromosomes, but males can produce gametes with both X and Y chromosomes.
d)When a male Y chromosome-containing gamete fertilizes with a female X chromosome-containing gamete, the result is a male fetus.
e)When a male X chromosome-containing gamete fertilizes with a female X chromosome-containing gamete, the fetus is female.
Ans : All the above
======================================== 71)Who rediscovered Mendel’s Work (the birth of Genetics)?
Ans : It was in 1900 AD that three botanists independently rediscovered the principles of heredity already worked out by Mendel.
They were :–
1)Karl Correns – Germany – Worked on maize (Zea mays). 2)Hugo de Vries – Holland – Worked on evening primrose (Oenothera). 3)Erich von Tschermak – Austria – Worked on flowering plants.
Correns gave the two law of Mendelism – law of segregation and law of independent assortment.
Hugo de Vries also found out the paper of Mendel and got it published in “Flora” in 1901.
Bateson, Punnet and other subsequent workers found Mendel’s work to be of universal application including animals.
=======================================
Question: Who coined the word Genetics ?
Ans : The word Genetics was coined by an English biologist William Bateson in 1905 [regarded as Father of Modern Genetics. The word
Genetics is derived from a greek word ‘gen’ meaning to become or to grow into. Genetics is the branch of biology which deals with the study of heredity and variation.
============================================
Autoploids commonly occur as a result of duplication of the genome(s) of a single species, thus, the genomes possessed by an autoploid are identical. An autotetraploid (4x) has four sets of the same genome, e.g., four sets of the A genome (AAAA).
Note:Reduced fertility—Abnormalities in meiosis may interfere with chromosome pairing, resulting in unbalanced chromosomal distribution between daughter cells, and thus, nonviable gametes. Gametes possessing an extra chromosome or missing a chromosome (i.e., aneuploids) are usually nonviable. This feature is utilized by breeders to develop seedless crops such as seedless watermelon. ===========================================
What is ‘ploidy ‘ ?
Ans : ‘Ploidy’ refers to the number of chromosome sets in a cell. Prefixes are used to specify the number of chromosome sets in a particular organism. The symbol x is used to indicate the number of chromosomes in a set.
1)Monoploids have one set (1x) and diploids have two sets (2x) of chromosomes, and so forth.
2)Haploidy—individual with half (n=x) of the somatic cell chromosome number.
3) Diploidy—individual with two sets of the basic, complete genome (2n=2x).
4)Polyploidy—individual with more than two basic, complete sets of chromosomes in its somatic cells. Among polyploids, there are two main types:
5)Autoploidy:- Autoploidy individual has more than two complete
chromosome sets from a single genome. Also known as autopolyploidy.
6)Allopoidy: Alloploidy individual has two or more genomes contributed from different parental species in their ancestral lineage. Also known as allopolyploidy. Most naturally occurring polyploids are alloploids.
7)Amphidiploids: Amphidiploids (also called amphiploids) are allotetraploids that contain two sets of genomes from each of two different parents. Amphidiploids are so-called because they behave like diploids during meiosis.
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