Science: Middle School: Grades 6, 7 and 8 Quiz - Genetics (Questions)

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Genes are the very basic molecular unit of inheritance in every living organism. The study of genes is known as Genetics.

Have you ever wondered why some people have blue eyes while others have brown? Or why some people are tall and some people are short? And then there’s hair color – why blond, brunette, auburn or red hair? All of these traits, and many, many others, including health issues, are passed down through generations in a family. We refer to this as traits that are inherited. Each inherited trait is found in the genes of a living thing.

The smallest unit of life is a cell.

A cell is the basic structure of all known living organisms. Each cell contains protoplasm enclosed within a membrane. The number of cells in living things varies from species to species but humans are made up of some 100 trillion cells. Each cell in the human body contains 25,000 to 35,000 genes. Each gene carries a genetic code or blueprint of inherited traits. This blueprint is called DNA.

DNA is organized into chromosomes. Chromosomes are tiny spaghetti-like structures to which the genes cling to. Chromosomes come in matching pairs. There are hundreds, if not thousands, of genes in just one chromosome.

Each cell has a nucleus that acts rather like the brain of the cell. It tells the cell what to do. Even though the nucleus is extremely small, it contains more information in it than several volumes of books.

In humans, a cell nucleus contains a total of 46 individual chromosomes. As chromosomes come in pairs, this means that there are 23 pairs of chromosomes. The father contributes 23 chromosomes and the mother contributes 23 chromosomes to make up the 23 pairs.

There are different kinds of inherited traits. These include dominate traits and recessive traits.

Dominate traits can push aside other family traits. For example, if one parent has brown eyes and one parent has blue eyes, chances are higher that their offspring will have brown eyes as brown is more dominate than blue. However, blue can sometimes win or you can get a mix and the offspring will have hazel eyes.

Recessive traits are traits that are pushed aside by a dominate trait. Using the example above, even if the offspring has the gene of producing blue eyes, the brown eye gene pushes it aside.