Lesson 2
Transcription and translation (discussed in the next lesson) are the two processes that form protein in our bodies. Protein is made up of amino acids (there are twenty different kinds of amino acids). It comes in many different arrays of organic compounds. A living organism must have protein in order to function. Proteins are so versatile, and there are so many of them (approximately 30,000 exist for humans) that their functions reflect this. Some proteins make up hormones, some are tough fibers that make hair and connective tissue, and yet others carry hereditary characteristics in the form of genes.
A gene is a section of genetic material called DNA (DeoxyRibonucleicAcid). It governs the inheritance of a certain group of traits, or even a singular characteristic or trait. Genes are located on chromosomes. Each gene occupies a locus, or place on the chromosome. DNA is a molecule that provides the structure for the chromosome, and the description of the gene.
The most successful model of the gene was proposed by Francis Harry Compton Crick and James Dewey Watson in 1953. They said that the DNA molecule is a long doublestrand that is twisted around itself, creating what is called a double helix. Each of the DNA strands is made up of a chain of nucleotides which are made of a sugar (deoxyribose) a phosphate group and a base that contains nitrogen. There are four different kinds of nucleotides, each has a different base. The four different bases are, adenine (A), thymine (T), guanine (G), and cytosine (C). The nucleotides are joined together by their sugar and phosphate parts, and because of this, the sugars and phosphates are what give the strands their form. Each of the bases from one of the strands attaches to another base on the other strand, but there are some rules. The bases adenine and thymine may pair with each other but thymine may not pair with guanine or cytosine, and neither can adenine. Guanine and cytosine may pair but, obviously, they cannot pair with the other two bases.
When a cell splits via mitosis, its chromosomes have replicated, meaning that the DNA has replicated. The double strands of DNA are attached to each other because of the matching base pairs, but the attachment is a weak one. When the DNA must replicate it simply has two unzip itself, and then complementary strands form. Here's and example, imagine a gene on the DNA that is about to be replicated. This gene is coded as follows:
A-T
T-A
C-G
C-G
T-A
A-T
G-C
C-G
A-T
The dashes are a symbol of the connection between base pairs. Okay, now the DNA unzips, so we have two single strands floating around:
A T
T A
C G
C G
T A
A T
G C
C G
A T
Now complementary strands connect themselves to the two originals:
A-T A-T
T-A T-A
C-G C-G
C-G C-G
T-A T-A
A-T A-T
G-C G-C
C-G C-G
A-T A-T
And wa la! we've got two identical copies of the original section of DNA. This of course goes on not just through one section, but through the whole piece of DNA.
Genes control the traits that make us what we are, but how do they do this? The genes do it through proteins. Genes are essentially an instruction set for the building of protein. They determine which kind of protein it is and what function it has. This means that if you possess a gene that has the instruction to assemble a hair protein that is curly, you'll have curly hair. To sum it up, genes determine whether or not your body will generate specific proteins that ultimately express themselves as traits. Genes get their instructions through transcription and translation.
On to Lesson 3 -- Transcription and Translation (And Other Related Things)