Vardaan Learning Institute

Ans: (b) Genotype
Genotype describes the genetic makeup (e.g., TT, Tt), while phenotype describes the physical appearance.

Ans: (b) 50%
Cross between Tt (Heterozygous Tall) and tt (Homozygous Dwarf) yields 50% Tall (Tt) and 50% Dwarf (tt).

Ans: (b) XY
Males have XY chromosomes while females have XX.

Ans: (d) Wrinkled Seed
Tall, Round, and Green Pod are dominant traits. Wrinkled seed is recessive.

Ans: (c) They had many contrasting characters
Peas had distinct traits (tall/short, violet/white flowers) which made them ideal for study.

Ans: (b) Gregor Johann Mendel
Mendel is known as the Father of Genetics for his work on pea plants.

Ans: (b) Girl
Mother always contributes X. If Father contributes X, the zygote is XX (Girl). If Father contributes Y, the zygote is XY (Boy).

Ans: (c) Colour of eyes
Eye colour is genetically determined and passed from parents to offspring. The others are acquired traits.

Ans: (d) 100%, 75%
TT x tt -> F1 is Tt (100% Tall). F1 x F1 (Tt x Tt) -> F2 is TT, Tt, Tt, tt (3 Tall : 1 Dwarf), so 75% Tall.

Ans: (b) The Y chromosome in zygote
Presence of Y chromosome triggers male development.

Ans: (a) Both A and R are true and R is the correct explanation of A.
Father produces two types of sperms (X and Y). If Y sperm fertilizes egg (X), child is male. Hence father determines sex.

Ans: (d) A is false but R is true.
Variations generally *increase* the chances of survival (e.g., heat resistant bacteria) in changing environments. A is false. R is true.

Ans: (a) Both A and R are true and R is the correct explanation of A.
In F1 generation, only dominant trait appears. Since all were violet, violet is dominant and white is recessive.

Ans: (c) A is true but R is false.
Traits are inherited independently (A is true). But TT x tt gives Tt (Tall), not medium height. Blending does not occur in simple Mendelian genetics.

(i) Gene: Functional unit of heredity located on DNA that controls a specific trait.
(ii) Heredity: Transmission of characters/traits from parents to offspring.
(iii) Variation: Differences in the characters among individuals of a species.

P: TT x tt $\rightarrow$ F1: Tt (All Tall).
F1 selfing: Tt x Tt.
F2: TT (Tall), Tt (Tall), Tt (Tall), tt (Dwarf).
Phenotypic Ratio: 3:1 (Tall : Dwarf).
Genotypic Ratio: 1:2:1 (TT : Tt : tt).

Female: XX, produce only X eggs.
Male: XY, produce X and Y sperms (50% each).
If X sperm fuses with egg $\rightarrow$ XX (Girl). If Y sperm fuses with egg $\rightarrow$ XY (Boy).

Genes control traits by synthesizing specific proteins. For example, a gene for tallness produces an enzyme (protein) that synthesizes plant growth hormones efficiently, resulting in a tall plant. If the gene is altered, the enzyme is less efficient, less hormone is produced, and the plant becomes dwarf.

Acquired Traits: Developed during lifetime, not passed to progeny (e.g., building muscles, knowledge).
Inherited Traits: Present from birth, passed to progeny via gametes (e.g., eye colour, blood group).

Genetic: In humans, sex is determined by sex chromosomes (XX or XY).
Environmental: In some reptiles like turtles, the temperature at which fertilized eggs are incubated determines the sex (high temp -> female, low temp -> male). In snails, individuals can change sex.

(i) F1 Genotype: RrYy.
(ii) F1 Phenotype: Round Yellow seeds.
(iii) F2 Phenotypic Ratio: 9 (Round Yellow) : 3 (Round Green) : 3 (Wrinkled Yellow) : 1 (Wrinkled Green).
(iv) Dominant: Round Shape / Yellow Color. Recessive: Wrinkled Shape / Green Color.

Law of Dominance: In a heterozygote, one allele (dominant) masks the expression of the other (recessive). e.g., Tt is Tall.
Law of Segregation: During gamete formation, the alleles pair separates so that each gamete receives only one allele. e.g., Tt separates into T and t.

(i) Short life cycle (can get results quickly) OR Many contrasting traits.
(ii) Phenotype: The observable physical appearance/trait of an organism.
(iii) Cross Tt x tt:
Gametes: (T, t) x (t).
Offspring: Tt (Tall), tt (Dwarf).
Fraction of dwarf = 1/2 or 50%.

(i) 50% (1/2).
(ii) Father (because he contributes either X or Y chromosome).
(iii) 23 pairs. 22 pairs are autosomes, 1 pair is sex chromosomes.