Inheritance in Biology

Inheritance in biology refers to the process by which traits or characteristics are passed from parents to their offspring. These traits include physical features, internal functions, and even certain behaviors. The basis of inheritance is DNA, which carries the instructions for building and operating living organisms.

Genes

A gene is a segment of DNA that contains the instructions for making a specific protein. Proteins carry out most of the functions in a cell and influence the traits that an organism shows.

Important points about genes:

1. Humans have more than twenty thousand genes.

2. Genes come in pairs. One copy is inherited from the mother and one from the father.

3. Different versions of a gene are called alleles.

4. Some alleles are dominant and some are recessive.

   • Dominant alleles show their effect even if only one copy is present.

   • Recessive alleles show their effect only when two copies are present.

Example: Brown eye color tends to be dominant. Blue eye color tends to be recessive.

Chromosomes

Chromosomes are long structures made of tightly coiled DNA and proteins. They act as storage units for genes.

Key facts:

1. Humans have 46 chromosomes, arranged in 23 pairs.

2. Twenty-two pairs are autosomes, and one pair consists of sex chromosomes.

3. Females have XX; males have XY.

4. Parents each contribute 23 chromosomes to their offspring.

How Genes Are Passed On

Genetic information moves from parent to offspring through the combined processes of meiosis and fertilization.