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Chapter 7: Inheritance

Download free PDF notes covering chromosome structure (thread-like structures of DNA and proteins, compact into thick chromatids during division, nucleosome consists of DNA wrapped around eight histone proteins, sister chromatids attached at centromere, telomeres as protective caps at ends), genotype vs phenotype (genotype is genetic makeup e.g., RR or Rr; phenotype is observable physical trait e.g., round seeds), alleles as different forms of a gene at same locus, Mendel's Law of Segregation (during gamete formation, two alleles for a trait separate so each gamete receives only one; pair restored at fertilization), Mendel's Law of Independent Assortment (alleles for different traits assort independently), monohybrid cross (3:1 phenotypic ratio, 1:2:1 genotypic ratio), dihybrid cross (9:3:3:1 phenotypic ratio), test cross (crossing dominant trait organism with homozygous recessive rr to determine if parent is homozygous dominant RR or heterozygous Rr based on offspring phenotypes), and nucleosome structure - strictly according to FBISE 2026 SLOs.

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Chapter Overview & SLOs

What is inheritance? Inheritance is the transmission of genetic information from parents to offspring. It explains how traits are passed from one generation to the next.

What is the basic organization of a chromosome? Chromosomes are thread-like structures made of DNA and proteins. During division, they compact into thick chromatids to prevent damage.

  • Nucleosome: Consists of DNA wrapped around eight histone proteins (like beads on a string).
  • Sister chromatids: Two identical copies of a chromosome attached at the centromere.
  • Centromere: Constricted region where sister chromatids are attached.
  • Telomeres: Protective caps at the ends of chromosomes to prevent degradation of genetic information.

How do Genotype and Phenotype differ?

  • Genotype: The specific genetic makeup of an individual (e.g., RR or Rr).
  • Phenotype: The observable physical trait expressed (e.g., round seeds).
  • Alleles: Different forms of a gene located at the same locus on homologous chromosomes.

What is Mendel''s Law of Segregation? During gamete formation, the two alleles for a trait segregate (separate) so each gamete receives only one allele. The pair is restored when gametes are fertilized.

What is Mendel''s Law of Independent Assortment? Alleles for different traits assort independently during gamete formation. This explains the 9:3:3:1 ratio in dihybrid crosses.

What are the results of a monohybrid cross? A monohybrid cross involves one trait:

  • Phenotypic ratio: 3:1 (dominant : recessive)
  • Genotypic ratio: 1:2:1 (RR : Rr : rr)

What are the results of a dihybrid cross? A dihybrid cross involves two traits (e.g., seed shape and color) and results in a phenotypic ratio of 9:3:3:1, demonstrating independent assortment.

What is a test cross? A test cross is used to determine an unknown genotype. By crossing an organism showing a dominant trait with a homozygous recessive (rr) individual, we can identify if the parent is homozygous dominant (RR) or heterozygous (Rr) based on the offspring''s phenotypes.

These notes are strictly aligned with the Student Learning Outcomes (SLOs) for the FBISE 2026 annual examination.

  • How do we describe the parts of a chromosome? A chromosome consists of sister chromatids attached at a constricted region called the centromere, with protective repetitive nucleotide sequences known as telomeres at the ends. DNA is wrapped around eight histone proteins to form nucleosomes.
  • How does the Law of Segregation ensure genetic inheritance? During gamete formation, the two alleles for a trait segregate (separate) so each gamete receives only one; the pair is restored when gametes are fertilized.
  • How do we interpret the results of a dihybrid cross? Crossing individuals for two traits (e.g., seed shape and color) results in a phenotypic ratio of 9:3:3:1, demonstrating that alleles for different traits assort independently (Law of Independent Assortment).
  • How can a test cross determine an unknown genotype? By crossing an organism showing a dominant trait with a homozygous recessive (rr) individual, we can identify if the parent is homozygous dominant (RR) or heterozygous (Rr) based on the offspring's phenotypes.

Frequently Asked Questions (FAQ)

1. Are these Class 10 Biology notes based on the latest FBISE syllabus for 2026?
Yes, these notes are strictly designed according to the Student Learning Outcomes (SLO) provided by the Federal Board (FBISE) for the 2026 academic year. We regularly update our content to match the latest curriculum changes and exam patterns.

2. Do these Biology 7 notes include solved exercise questions and diagrams?
Absolutely. These notes contain comprehensive solutions to all textbook exercise questions, including Multiple Choice Questions (MCQs), Short Questions, and detailed Long Questions. We also include labeled diagrams and key definitions to help you secure maximum marks in your board exams.

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