-: Questions :-

Q1. Who is the father of modern genetics?
Answer: The science of genetics is generally said to have been founded by Gregory John Mendel. He is considered the Father of Genetics due to his experiments on garden peas and the formulation of his laws of inheritance.

Q2. What is heredity?
Answer: Heredity is the transmission of physical traits from parents to offspring. It is part of the modern experimental study of the laws of inheritance, which is the field of genetics.

Q3. For how many years Mendel carried out his experiment?
Answer: The document mentions that Mendel published his important conclusions in regard to heredity in 1866. It does not explicitly state the number of years he carried out his experiment.

Q4. Where Mendel published his result?
Answer: Mendel published his important conclusions in regard to heredity in the proceedings of the Natural History Society of Brunn.

Q5. Who rediscovered Mendel laws of inheritance?
Answer: Mendel’s laws were rediscovered in 1900, sixteen years after his death, by three European scientists: Correns, De-Vries, and Von Tshermak.

Q6. What is Mendel’s monohybrid ratio?
Answer: Mendel’s monohybrid ratio, based on the cross of a single contrasting character (like tallness vs. dwarfness), is:
Phenotypic ratio: 3:1 (3 Dominant: 1 Recessive, e.g., 3 Tall: 1 Dwarf).
Genotypic ratio: 1:2:1 (1 Homozygous Dominant: 2 Heterozygous: 1 Homozygous Recessive, e.g., 1 TT: 2 T(D): 1 DD).

Q7. What is gene?
Answer: A gene is the basic unit of inheritance. Genes are located in the chromosome and are arranged in a single linear order. They determine the biological characteristics in a living system and are capable of duplicating themselves (replication). The concept of the gene was proposed by Sutton in 1902, and the term was first used by Johannsen in 1909.

Q8. What is Mendel’s dihybrid ratio?
Answer: Mendel’s dihybrid ratio, which considers the simultaneous inheritance of two pairs of contrasting characters, is 9:3:3:1.
The four combinations in this phenotypic ratio are:
9 Round Tall (Double Dominant)
3 Wrinkled Tall (One Recessive, One Dominant)
3 Round Dwarf (One Dominant, One Recessive)
1 Wrinkled Dwarf (Double Recessive)

Q9. What is eugenics?
Answer: Eugenics is the science of bringing into the world only the good germplasm, or improving the genetic qualities of individuals yet to be born by exercising selective mating. It was defined by Galton as “The study of eugenics under social control which may improve the racial qualities of future generations, both physically and mentally with the application of principles of genetics”.

Q10. Who is the father of eugenics?
Answer: Sir Francis Galton, an English statistician, demographer, and ethnologist, is considered the father of Eugenics. He established this discipline in 1883.

Q11. What are the two types of eugenics?
Answer: The two types of eugenics are:

1. Positive Eugenics: Aimed to improve the human race by encouraging individuals with desirable traits to breed.
2. Negative Eugenics: Focused on reducing “degenerate offspring” by preventing or eliminating those with undesirable traits from breeding, often through sterilization or segregation.

Q12. What is another name for down syndrome?
Answer: Another name for Down’s Syndrome is Mongoloid Idiocy or Trisomy 21.

Q13. What is the number of chromosomes in a female having Turner syndrome?
Answer: A female with Turner’s Syndrome has 45 chromosomes instead of the normal 46. Their chromosomal constitution is XO because one of the X chromosomes is missing, partially or completely.

Q14. Who discovered Klinefelter syndrome?
Answer: Dr. Henry Klinefelter discovered and identified this syndrome in 1950.

Q15. Write a short note on down syndrome.
Answer: Down Syndrome, also known as Trisomy 21 or historically as Mongoloid Idiocy, was first described by Langdon Down in 1866. It is a chromosomal disorder caused by the presence of an extra copy of the 21st chromosome, giving the individual 47 chromosomes instead of the normal 46. This genetic abnormality leads to several characteristic features, including short stature, stubby hands and feet, a fissured tongue, epicanthic eye folds, and intellectual disability. Individuals with Down Syndrome often exhibit a cheerful, friendly, and sociable behavior, making them distinct in personality despite their physical and cognitive challenges.

Q16. Write short note on:

(a) Turner Syndrome
Answer: This syndrome was first described by Henri Turner in 1938 and is the most common sex chromosomal abnormality found in females. It results from a numerical aberration of sex chromosomes where one X chromosome is missing (partially or completely). The chromosomal constitution is XO (45 chromosomes). The individual is treated as a female with an abnormal genotype and is often an “incomplete female” due to lack of the second X chromosome.

(b) Klinefelter Syndrome
Answer: This syndrome was discovered by Dr. Henry Klinefelter in 1950 and affects males. It is caused by an additional X chromosome (47 chromosomes — 44+XXY). Patients have underdeveloped testicles, sterility, sparse body hair, long legs, and may develop small female-like breasts (gynaecomastia).

(c) Eugenics
Answer: Eugenics, established by Sir Francis Galton in 1883, focuses on improving human genetic traits. It promotes higher reproduction of people with desired traits (Positive Eugenics) and restricts reproduction of those with undesired traits (Negative Eugenics). However, it was later criticized for unethical applications during Nazi Germany.

(d) Gene and Allele
Answer: A gene is the basic unit of inheritance, located on chromosomes, that carries coded information responsible for the development and functioning of specific traits in an organism. Each gene can exist in different forms, called alleles, which occupy the same position, or locus, on homologous chromosomes. Alleles determine variations in a particular trait; for example, in pea plants, the gene for plant height has alleles ‘T’ (tall) and ‘D’ (dwarf), which control whether the plant grows tall or short.

(e) Genotype and Phenotype
Answer: The genotype of an organism refers to its total genetic makeup, representing the combination of alleles present for a particular trait. For example, in pea plants, the height gene can have genotypes TT, TD, or DD. The phenotype is the observable physical appearance or characteristics of an organism, which results from the interaction of its genotype with the environment. For instance, depending on the genotype, a pea plant may appear tall or dwarf.

(f) Homozygous and Heterozygous
Answer: An organism is homozygous for a trait when both alleles for that gene are identical, such as TT or DD, resulting in a uniform expression of the trait. In contrast, an organism is heterozygous when the two alleles for a trait are different, such as TD, which is commonly seen in hybrid plants. The heterozygous condition may result in one allele being dominant, masking the effect of the other recessive allele in the phenotype.

Q17. Describe Mendel’s monohybrid ratio with a neat diagram.
Answer: The monohybrid ratio is obtained by studying the inheritance of a single pair of contrasting traits, such as tallness (T) and dwarfness (D) in pea plants. In the parental generation (P), a pure-bred tall plant (TT) was crossed with a pure-bred dwarf plant (DD). In the F₁ generation, all the offspring were tall, indicating that tallness is the dominant trait, and their genotype was heterozygous (T(D)). When the F₁ hybrids were self-fertilized to produce the F₂ generation, the offspring displayed tall and dwarf plants in a ratio of 3:1, demonstrating the segregation of alleles according to Mendel’s law of dominance.

P: TT × DD
│
F₁: T(D) (All Tall)
│
F₂: T(D) × T(D)
┌─────┬─────┐
TT T(D) DD

• Phenotype: Tall Tall Dwarf
• Genotypic Ratio: 1 2 1 
• Phenotypic Ratio = Tall : Dwarf : : 3 : 1 Dwarf

Q18. Describe Mendel’s dihybrid ratio.
Answer: Mendel’s Law of Independent Assortment states that two or more traits are inherited independently of each other. In the parental generation (P), a pure-bred Tall Round (RRTT) pea plant was crossed with a pure-bred Dwarf Wrinkled (rrtt) plant. All offspring in the F₁ generation were Tall Round (RrTt), showing that tallness and roundness are dominant traits. When the F₁ hybrids were self-fertilized, the F₂ generation displayed a phenotypic ratio of 9:3:3:1, consisting of 9 Round Tall, 3 Wrinkled Tall, 3 Round Dwarf, and 1 Wrinkled Dwarf, demonstrating that the two traits segregate independently according to Mendel’s principle.