Inheritance
1. Inheritance
Inheritance is the process by which traits (characteristics) are passed from parents to their offspring.
What are traits?
Traits are features such as:
Eye color
Hair color
Height
Blood group
Shape of nose
Intelligence (partly)
Why inheritance happens
Inheritance happens because parents pass genes to their children.
Types of inherited traits
Physical traits – height, skin color
Physiological traits – blood group
Behavioral traits – talents, temperament (partly)
Example
If both parents have brown eyes, the child is likely to have brown eyes.
Blood group is inherited from parents.
2. Genes
Genes are the units of inheritance.
What are genes?
Genes are small sections of DNA
They carry instructions for making proteins
These proteins decide traits
Where are genes found?
Genes are located on chromosomes
Chromosomes are inside the nucleus of a cell
Function of genes
Genes control:
Growth
Development
Appearance
Body functions
Example
A gene may decide whether hair is curly or straight.
3. Genes and Environment
Traits are influenced by both genes and environment.
Genes
Provide the potential
Decide what can happen
Environment
Decides how much of that potential is expressed
Examples
Height
Genes decide height potential
Nutrition decides actual height
Intelligence
Genes give ability
Education and practice improve it
Skin color
Genes decide base color
Sun exposure changes shade
Conclusion
👉 Genes load the gun, environment pulls the trigger
4. Genes and Chromosomes
Chromosomes
Thread-like structures
Made of DNA and proteins
Humans have 46 chromosomes (23 pairs)
Relationship between genes and chromosomes
Chromosomes are like books
Genes are like sentences inside the book
Types of chromosomes
Autosomes – 22 pairs (control body traits)
Sex chromosomes – 1 pair (XX in females, XY in males)
Genes on chromosomes
Each chromosome carries many genes
Genes are arranged in a specific order
5. Passing On Genes
How genes are passed
Genes are passed through reproductive cells:
Sperm (father)
Egg (mother)
During fertilization
Sperm gives 23 chromosomes
Egg gives 23 chromosomes
Child gets 46 chromosomes
Why children resemble parents
Half of genes come from mother
Half come from father
Variation
Every child gets a different combination of genes
This causes differences between siblings
Example
One sibling may resemble father
Another may resemble mother