Class 10 Science - PUNJAB
Heredity
The chapter 'Heredity' in Class 10 Science explores how traits and characteristics are passed down from parents to offspring through generations. Students will learn about Gregor Mendel's groundbreaking experiments on pea plants, understanding concepts like dominant and recessive traits, genotypes, and phenotypes. The chapter also covers the mechanisms of sex determination in humans and the role of DNA. For the Punjab (PSEB) board exams, this is a high-scoring chapter that frequently features conceptual questions, cross-breeding problems, and diagram-based questions on monohybrid and dihybrid crosses, making a clear understanding of genetic terminology essential.
Start Learning FreeKey Concepts
Heredity
The transmission of characters or traits from parents to their offspring, which is responsible for similarities and variations among individuals of the same species.
Dominant and Recessive Traits
A dominant trait is expressed in the offspring even when only one copy is present (e.g., tallness in pea plants), while a recessive trait is masked unless two copies are present (e.g., dwarfness).
Genotype and Phenotype
Genotype refers to the genetic makeup of an organism (e.g., TT, Tt, tt), whereas phenotype is the observable physical or biochemical characteristic resulting from the genotype.
Mendel's Monohybrid Cross
A genetic cross focusing on a single pair of contrasting traits, which led Mendel to formulate the Law of Segregation and resulted in a 3:1 phenotypic ratio in the F2 generation.
Sex Determination in Humans
The process by which the sex of a newborn is determined by chromosomes; humans have 23 pairs, where females have XX and males have XY chromosomes, making the male sperm responsible for determining the child's sex.
Important Formulas
Board Exam Info
In the Punjab School Education Board (PSEB) Class 10 Science exam, the 'Heredity' chapter typically carries around 4 to 6 marks. Questions usually include 1-mark objective or fill-in-the-blank questions, short-answer questions defining terms like variations or heredity, and 3-to-5-mark long-answer questions involving Mendel's laws or drawing a Punnett square for a monohybrid cross.
Frequently Asked Questions
What is the difference between acquired and inherited traits?
Inherited traits are genetic characteristics passed from parents to offspring (like eye color) and can be passed to future generations. Acquired traits are developed during an individual's lifetime due to experience or environment (like muscle building) and cannot be inherited.
Why did Mendel choose pea plants for his experiments?
Mendel chose pea plants (Pisum sativum) because they have distinct contrasting characters, are easy to grow, have a short life cycle, and naturally self-pollinate but can also be easily cross-pollinated artificially.
How is the sex of a child determined in human beings?
Human females have two X chromosomes (XX) and produce eggs with an X chromosome. Males have an X and a Y chromosome (XY) and produce two types of sperm: 50% with X and 50% with Y. If a sperm carrying an X fertilizes the egg, it forms a girl (XX); if a Y-bearing sperm fertilizes the egg, it forms a boy (XY).
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