Download DNA info

DNA, Genes, & Chromosomes
Genes are the basic structural and functional unit of heredity. Together they form
chromosomes which are made up of DNA, histones, and other support proteins. Therefore
genes are found on DNA. All of the hereditary material could be called ‘instructions for making
a living thing’!
A gene is a specific segment of DNA that has a specific location on a chromosome. Humans
have 23 pairs of chromosomes. Our chromosomes come in pairs (expect for the x and the y
chromosome in males), and each pair is made up of a single molecule of double-stranded DNA
tightly coiled many times around a protein called a histone that supports its structure. If you
imagine this strand of DNA being uncoiled and stretched out, it might look like a long ladder.
The sides of the ladder are made from phosphate (sugar) groups and each rung of the ladder is
actually a base pair of proteins (Adenine & Thymine or Cytosine & Guanine. Segments of these
base pairs of varying lengths are called genes. Each gene contains a piece of genetic
information that tells the cell to make a specific protein. Thousands of genes are found on each
strand of DNA that makes up your chromosomes.
It has been thought that much of the length of DNA does not seem to code for any specific
protein and does not seem to be genes. This was long referred to as ‘junk DNA’ and is now
more often referred to as noncoding and structural DNA. Current evidence indicates that these
regions are important for regulating gene activity. They also help position DNA in threedimensional space within the nucleus, which in turn affects rates of gene expression. Put
another way, DNA has information stored in its folding patterns, not just in the GATC code of
the ‘ladder rungs’.