Heredity and Cell Nuclei

Study Notes

Building an Organism

A plan and building materials are necessary to build a living organism, similar to building a house.
The plan is found inside the nuclei of cells and consists of chemicals called genes.
Genes instruct the body to make proteins, which determine the shape and behavior of the body.
Each gene controls the production of one particular protein or a group of proteins.
Genes are joined together to make long strands called chromosomes.
Chromosomes and genes are made of deoxyribonucleic acid (DNA), which is a blueprint for life.

DNA and Chromosomes

DNA is a small part of a model that shows how the body is to be built.
Every cell in a living organism contains a copy of this plan.
When cells divide, DNA copies itself, and a copy of this plan is passed from one generation to the next.
This is the reason why we inherit characteristics from our parents.

Growth and Cell Division

All living things grow from a fertilized egg-cell.
The only way for the organism to grow is for this fertilized egg-cell to divide into two, then four, eight, sixteen cells, and so on.
Each time a cell divides, the plans for making the organism are passed on to the new cell.
Copies of the chromosomes and genes are made so that the plan is available in the new cells.

Mitosis

Mitosis is the process by which a cell and its nucleus divide into two.
The chromosomes make copies of themselves before the nucleus divides into two.
The individual chromosomes split along their length, and a web-like structure called a spindle begins to form.
The chromosomes arrange themselves around the equator of the spindle, and the halves of each chromosome, called chromatids, pull apart.
The chromatids are pulled towards the two poles of the spindle, and a new nuclear membrane begins to form around each daughter nucleus.

Inherited Characteristics

Humans inherit characteristics from both parents.
A gene is a set of chemical instructions that controls some detail of how to build a human or a plant.
Each gene controls the production of one particular protein or a group of proteins.

Description

Learn about the importance of cell nuclei in building a new organism. Understand how the plan for building a living organism is found inside the nuclei of its cells, similar to a blueprint for building a house.