Mechanism of Heredity Transmission

Every child inherits some traits from their parents, like hair type, height, eye color, or even behavior. Yet, no two children—even from the same parents—are exactly alike. This happens because of a biological process called hereditary transmission, which works at the time of conception.

• Hereditary transmission means the passing of traits and qualities from parents and ancestors to their children through genes at the time of conception.
• When the sperm from the father combine with the egg from the mother, a fertilized egg or zygote is formed.
• This zygote contains all the hereditary information needed for the growth and features of the child.

• Chromosomes are small, thread-like structures found in the nucleus of every cell.
• They are made up of DNA and carry genes, which are the real carriers of heredity.
• Each human cell has 46 chromosomes, arranged in 23 pairs.
• 23 comes from the father
• 23 comes from the mother
• Genes carry instructions that decide the physical and some mental traits of the child (for example: skin color, eye color, body shape, height, etc.).

• Every child receives half of their genes from the mother and half from the father.
• Which 50% of each parent’s genes are inherited is completely by chance.
• That’s why brothers and sisters from the same parents show different combinations of traits.
• Example: one child may inherit the father’s eye color and the mother’s hair type, while another child inherits the opposite.

• Each time a new sperm or egg cell forms, a different combination of genes is chosen.
• Therefore, every child gets a unique mixture of genes.
• This is why even though children come from the same parents, they look and behave differently.

• The selection of which traits will be passed to the child is fixed at the moment of conception.
• Once fertilization takes place, the combination of genes inside the fertilized egg cannot be changed, added to, or removed.
• Therefore, the inherited qualities are permanent and remain for the entire life.

According to Kuhlen and Thompson,

• The child inherits certain physical and mental qualities from its parents and ancestors only once — at the time of conception.
• These inherited materials (chromosomes and genes) remain fixed inside the fertilized egg and guide the child’s development throughout life.

• When germ cells (sperm and egg) are formed, a process called crossing over happens.
• In this process, paired chromosomes exchange small parts of genetic material.
• This increases the chances that every sperm and egg cell — and therefore every person — will be genetically different.
• Because of this, no two humans are genetically identical, except identical twins.

• Identical twins are formed when one fertilized egg splits into two identical parts.
• Both share the same genes and chromosomes, so they are genetically identical.
• All other people (even siblings) are genetically and biologically different.

• Hereditary transmission is the passing of traits from parents to children through genes at conception.
• A zygote is formed when a sperm and an egg combine, carrying all the hereditary information.
• Each child receives 23 chromosomes from each parent, making a total of 46.
• Genes (made of DNA) control physical and some mental traits, such as height, eye colour, and behaviour.
• Each child gets a unique combination of genes, so siblings are different from each other.
• Traits are fixed at conception and remain unchanged throughout life.
• Identical twins are the only ones with the same genes, while others are genetically different.