This chapter explains how traits and characteristics are passed from parents to offspring through the process of reproduction. It describes how variations arise and accumulate over generations, leading to diversity among living organisms. The chapter introduces the basic rules of inheritance discovered by Gregor Mendel, explaining concepts such as dominant and recessive traits, genes, and chromosomes. It also explains how traits are inherited independently, how genes control the expression of characteristics, and how sex determination takes place in human beings.
Key Points
Heredity is the transfer of traits from parents to offspring.
Variations arise during reproduction and may be inherited.
Variations help organisms survive in changing environments.
Asexual reproduction produces fewer variations than sexual reproduction.
Genes are units of inheritance present on DNA.
Each gene controls a specific trait.
In sexual reproduction, offspring inherit two copies of each gene, one from each parent.
Gregor Mendel studied inheritance using pea plants.
A dominant trait expresses itself even if one copy is present.
A recessive trait expresses itself only when both copies are recessive.
Mendel showed that traits are inherited in fixed patterns.
Traits for different characters can be inherited independently of each other.
Chromosomes carry genes and occur in pairs in body cells.
Gametes contain only one set of chromosomes.
Fertilisation restores the normal chromosome number.
In humans, sex determination depends on the X and Y chromosomes.
Females have XX chromosomes, while males have XY chromosomes.
The father determines the sex of the child.
👉 👉Heredity helps us understand how life continues with both similarities and differences. By learning how traits are inherited and how variations arise, we gain insight into diversity, evolution, and the responsibility of respecting and protecting life in all its forms.