• Heredity transfers traits from parents to offspring; variation arises more in sexual than asexual reproduction.
• Gene → Protein → Trait: DNA segment (gene) encodes protein; protein/enzymes influence hormones & structure → visible trait.
• Chromosome basics: DNA + proteins; visible in cell division; centromere position defines metacentric, sub-metacentric, acrocentric, telocentric.
• Humans: 46 (23 pairs) = 44 autosomes + XX/XY. Women: 44+XX; Men: 44+XY.
• DNA structure: Double helix; sugar–phosphate rails; A–T and G–C base pairing by H-bonds.
• RNA types: mRNA (message), tRNA (brings amino acids), rRNA (ribosome component).
• Mendel (pea plant): Mono-trait (monohybrid) gives F₂ phenotypic ratio \(3:1\), genotypic ratio \(1:2:1\). Two-trait (dihybrid) F₂ phenotypic ratio \(9:3:3:1\).
• Dominance: Dominant allele masks recessive in heterozygote; alleles segregate during gamete formation.
• Independent assortment: Allele pairs of different traits assort independently in gametes (seen in dihybrid cross).
• Genetic disorders:
  • Chromosomal number changes: Down (trisomy 21 → 47, 46+1), Turner (44+X), Klinefelter (44+XXY).
  • Monogenic (single-gene): albinism, sickle-cell anaemia, haemophilia, PKU, CF, etc.
  • Mitochondrial (maternal): e.g., Leber hereditary optic neuropathy.
  • Polygenic: cleft palate, diabetes, hypertension, heart disease, asthma, obesity—gene × environment.
• Sickle-cell genetics: Genotypes—AA (normal), AS (carrier), SS (sufferer). Match-ups decide risk; carriers should avoid marrying carriers/sufferers.

1) Who is the Father of Genetics?

Gregor Johann Mendel.

2) Unit of heredity?

Gene.

3) Chemical nature of genes?

DNA segments.

4) Human chromosome number?

46 (23 pairs) → 44 autosomes + 2 allosomes.

5) Base pair rules in DNA?

A–T and G–C.

6) Define allele.

Alternative forms of a gene controlling the same trait.

7) Phenotype vs genotype (one line)?

Phenotype = visible trait; genotype = allele combination.

8) F₂ monohybrid phenotypic ratio?

\(3:1\) (dominant:recessive).

9) F₂ monohybrid genotypic ratio?

\(1:2:1\) (TT:Tt:tt).

10) F₂ dihybrid phenotypic ratio?

\(9:3:3:1\).

11) Law explaining 3:1?

Law of Segregation.

12) Law explaining 9:3:3:1?

Law of Independent Assortment.

13) Carrier genotype in sickle-cell?

AS.

14) Trisomy of 21 causes?

Down syndrome.

15) 44+X condition named?

Turner syndrome (female, monosomy X).

16) 44+XXY condition named?

Klinefelter syndrome (male).

17) The double-helix model was proposed by?

Watson and Crick (1953).

18) Three types of RNA?

mRNA, tRNA, rRNA.

19) DNA fingerprinting is used for?

Lineage/criminal identification (unique DNA profile).

20) Example of a polygenic disorder?

Diabetes / Hypertension / Cleft palate (any one).

1) What composes a nucleotide?

Sugar (deoxyribose), phosphate, and a nitrogenous base.

2) Which bases are purines?

Adenine and Guanine.

3) Which bases are pyrimidines?

Cytosine and Thymine (Uracil in RNA).

4) Define homologous chromosomes.

A pair similar in size/shape/genes (one maternal, one paternal).

5) Name four centromere-based chromosome types.

Metacentric, Sub-metacentric, Acrocentric, Telocentric.

6) What is a monohybrid cross?

A cross involving one pair of contrasting traits.

7) Why are F₁ monohybrids uniform?

Dominance masks recessive allele (all show dominant phenotype).

8) Write Mendel’s F₂ genotypic ratio for monohybrid.

\(1\,\text{TT} : 2\,\text{Tt} : 1\,\text{tt}\).

9) In dihybrid F₁, how many gamete types form?

Four: RY, Ry, rY, ry.

10) Define independent assortment.

Allele pairs separate independently into gametes.

11) What fails to form in albinism?

Melanin pigment.

12) Molecular change in sickle-cell Hb?

Glu (6th) → Val substitution in β-chain.

13) Inheritance in mitochondrial disorders?

Maternal (ovum provides mitochondria).

14) Give two symptoms of Down syndrome.

Intellectual disability, characteristic facial features/short stature.

15) State sex chromosomes in male.

XY.

16) State sex chromosomes in female.

XX.

17) What is DNA fingerprinting?

Profiling unique DNA sequence to identify individuals.

18) rRNA’s role?

Forms ribosomes where proteins are synthesized.

19) tRNA’s role?

Transfers specific amino acids to ribosome per mRNA code.

20) Why genetic counselling before marriage (certain areas)?

To detect carriers (e.g., sickle-cell) and reduce disease risk in offspring.

1) Relate gene → enzyme → hormone → trait (plant height).

Gene encodes enzyme; efficient enzyme elevates hormone (growth hormone) level → taller phenotype.

2) Distinguish phenotype and genotype with example.

Phenotype = tall plant; genotype could be TT or Tt—same look, different alleles.

3) Explain Law of Segregation.

Alleles separate during gamete formation; each gamete gets one allele, giving F₂ 1:2:1 genotypes.

4) Give dihybrid F₂ phenotypic ratio with categories.

\(9\) Round-Yellow : \(3\) Round-Green : \(3\) Wrinkled-Yellow : \(1\) Wrinkled-Green.

5) Why did F₁ of dihybrid show only Round-Yellow?

Round (R) and Yellow (Y) are dominant over wrinkled (r) and green (y); F₁ genotype RrYy appears Round-Yellow.

6) Write the gametes from RrYy.

RY, Ry, rY, ry (all four in equal proportion).

7) What are autosomes and allosomes?

Autosomes: non-sex chromosomes (22 pairs in humans). Allosomes: sex chromosomes (XX/XY).

8) List centromere positions with shapes.

Metacentric (V), Sub-metacentric (L), Acrocentric (j), Telocentric (i).

9) Mention two features each: DNA vs RNA.

DNA: deoxyribose, A-T/G-C, double helix. RNA: ribose, A-U/G-C, single-stranded (mostly).

10) Why is F₂ monohybrid phenotypic 3:1 but genotypic 1:2:1?

Heterozygotes (Tt) look like TT (dominant), masking recessive tt.

11) Describe two key symptoms of sickle-cell anaemia.

Pain crises & anaemia due to sickling and haemolysis; fatigue/organ damage due to low O₂ carriage.

12) Suggest two preventive steps for sickle-cell spread.

Screening (solubility test/electrophoresis); avoid carrier × carrier or carrier × sufferer marriages.

13) State karyotypes for three chromosomal disorders.

Down: \(47\) (trisomy 21). Turner: \(44+X\). Klinefelter: \(44+XXY\).

14) Why are mitochondrial disorders maternal?

Zygote receives mitochondria almost exclusively from ovum (mother).

15) Give examples of monogenic vs polygenic.

Monogenic: albinism, haemophilia. Polygenic: diabetes, hypertension.

16) Write the meaning of DNA fingerprinting and one use.

Unique DNA profiling; used in forensics/parentage testing.

17) What is independent assortment’s outcome in gametes?

All allele combinations appear with equal probability (RY, Ry, rY, ry).

18) Why do sexually produced offspring show more variation?

Meiosis (independent assortment, crossing over) and random fertilization mix alleles.

19) Define carrier.

Heterozygote for a recessive disease allele (phenotypically normal, can pass allele).

20) State one social action to reduce tobacco-linked cancers.

Awareness drives; avoid smoking/chewing tobacco; strict regulations on sales/ads.

1) Complete the sentences (choose correct words).

a) Hereditary characters are transferred by genes; hence they are structural and functional units of heredity.
b) Organisms produced by asexual reproduction show minor variations.
c) The nuclear component carrying hereditary characteristics is the chromosome.
d) Chromosomes are mainly made up of DNA (and proteins).
e) Organisms produced through sexual reproduction show major variations.

2) Explain (any as asked).

a) Mendel’s monohybrid progeny (Tall × Dwarf): P: TT × tt → F₁ all Tt (all tall). Selfing F₁: Tt × Tt → F₂ \(1\) TT : \(2\) Tt : \(1\) tt (phenotype \(3\) tall : \(1\) dwarf).
b) Dihybrid ratio: P: RRYY × rryy → F₁ all RrYy (Round-Yellow). Selfing: RrYy × RrYy → F₂ phenotypes \(9\) RY : \(3\) Ry : \(3\) rY : \(1\) ry i.e. \(9:3:3:1\).
c) Monohybrid vs Dihybrid: One trait vs two traits; F₂ \(3:1\) vs \(9:3:3:1\); single allele pair segregation vs independent assortment of two allele pairs.
d) Is avoidance of persons with genetic disorder right? No. Genetic disorders require care, counselling and inclusion, not stigma. Focus on screening, management, and informed marital counselling where relevant.

3) Answer in your own words.

a) Chromosome & types: DNA-protein bodies in nucleus carrying genes. Types by centromere: metacentric, sub-metacentric, acrocentric, telocentric.
b) DNA structure: Double helix; anti-parallel sugar–phosphate backbones; base pairs A–T, G–C via H-bonds; genes are specific base sequences.
c) Use of DNA fingerprinting: Unique identity for crime investigation, paternity disputes, disaster victim ID—high accuracy when used ethically.
d) RNA—structure/function/types: Ribose sugar, bases A/U/G/C; single-stranded. mRNA (message), tRNA (amino acid carrier), rRNA (ribosome).
e) Need for blood tests before marriage (certain regions): Detect carriers of heritable disorders (e.g., sickle-cell); genetic counselling reduces disease burden.

4) Brief notes.

a) Down syndrome: Trisomy 21 (47 chromosomes). Features: intellectual disability, characteristic face, short stature; reduced lifespan.
b) Monogenic disorders: Single-gene defects; product absent/defective → abnormal metabolism. Examples: albinism, Tay-Sachs, PKU, CF, haemophilia.
c) Sickle-cell—symptoms/treatment: Pain crises, anaemia, fatigue; confirmed by electrophoresis. Management: folic acid, hydration, pain control, avoid infections; genetic counselling.

5) Inter-relate items in A, B, C.

Leber hereditary optic neuropathy → Mitochondrial disorder (maternal).
Albinism → Monogenic disorder (pale skin/white hairs).
Diabetes → Polygenic disorder (affects blood-glucose level).
Turner syndrome → 44+X (women are sterile).
Klinefelter syndrome → 44+XXY (men are sterile).

6) Fill in the blanks based on the relationship.

a) 44+X : Turner syndrome :: 44+XXY : Klinefelter syndrome.
b) 3:1 Monohybrid :: 9:3:3:1 : Dihybrid.
c) Women : Turner syndrome :: Men : Klinefelter syndrome.

7) Complete the tree (types of hereditary disorders).

Hereditary disorders → (i) Chromosomal (number/structure; e.g., Down, Turner, Klinefelter) • (ii) Monogenic (single-gene; e.g., albinism, sickle-cell) • (iii) Mitochondrial (maternal; e.g., LHON) • (iv) Polygenic (multi-gene + environment; e.g., diabetes, BP).

• Monohybrid F₂: \( \text{Phenotype } 3:1,\; \text{Genotype } 1:2:1 \).
• Dihybrid F₂: \( 9:3:3:1 \) for dominant–dominant, dominant–recessive, recessive–dominant, recessive–recessive.
• Gametes from \( \text{RrYy} \): \( \{ \text{RY}, \text{Ry}, \text{rY}, \text{ry} \} \).