What Is Genetics?

Genetics is the study of how different qualities, called traits, are passed down from parents to child. Genetics helps explain what makes you unique, why family members look alike, and why some diseases run in families. When we trace the paths of these qualities, we are following packages of information called genes.

How Do Genes Work?

Your body is made up of trillions of tiny cells. Almost every cell in your body has a nucleus, a sort of headquarters that contains your genes. Your mix of genes is unique to you—even your full brothers or sisters have a slightly different mix. Genes are instructions for building the parts of your body and doing the work that keeps you alive, from carrying oxygen to digesting to food and everything else we do. The genes are grouped into collections called chromosomes. Most humans have 23 pairs of chromosomes.


A specific characteristic of an individual.


The basic unit of inheritance. Genes are made up of DNA and are arranged along a chromosome.


The basic building blocks of all living things.


A membrane-bounded region inside each cell that provides a sanctuary for genetic information, including the long strands of DNA that encode this genetic information.


In humans, chromosomes are found in the cell nucleus and are made of DNA and proteins. Chromosomes carry genetic information.

What is DNA?

Deoxyribonucleic acid (DNA) is made of four molecules called bases, which are abbreviated as letters:

A = Adenine

T = Thymine

C = Cytosine

G = Guanine

Structure of DNA

The letters or bases are linked together to make a strand of DNA. Two strands of DNA are paired together and form a structure called a double helix.

·        Adenine, A, is always paired with thymine, T.

·        Cytosine, C, is always paired with guanine, G.

The three-dimensional shape of a double helix looks like a twisted ladder. The paired bases (A-T and C-G) are like the rungs of the ladder.

Genes are made of DNA

The language of genetics has only four letters (A,T,C, and G).  These four letters are combined

Into three-letter words.  The words make up “genes” which are like sentences.  Each sentence has an important meaning or story to tell.  Genes provide the instructions to keep cells in your body doing their jobs.

Genes are packaged into chromosomes

DNA is organized into about 20,000 genes, and genes are packaged into chromosomes.  You can think of your entire genetic code as a set of encyclopedias, and each chromosome as a separate volume.  Normally, a person inherits half of their chromosomes from their mother and the other half from their father.  

Most people have 23 pairs of chromosomes, for a total of 46 chromosomes.

Chromosomes are called “sex chromosomes” and “autosomes”

Of these 46 chromosomes, two chromosomes determine if a baby is a male or female.  The sex chromosomes are called “X” and “Y”.  Most males have one X chromosome and one Y chromosome.  Most females have two X chromosomes.  In addition to the two sex chromosomes, the other chromosomes are called “autosomes” and are numbered 1-22.


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