DNA-The Code of Life Mr. Price 7 th Grade

What is DNA? DNA stands for deoxyribonucleic acid. DNA is a chemical that controls the activities of cells with coded instructions. It tells your cells what to look like and how to behave. Through cell division DNA is passed on to new cells.

Structure of DNA DNA has two twisted strands of sugar and phosphate molecules held apart by pairs of nitrogen bases. This makes it look like a twisted ladder. The nitrogen bases always pair up with the same partner. Adenine-Thymine Guanine-Cytosine

I Like Your “Genes” Genes are small sections of DNA that make up our chromosomes. Initially it was hypothesized that human cells had anywhere from 100,000-1,000,000 different types of genes. Back in the mid 1990’s and earlier 2000’s the entire genome (genetic sequence) for human’s was mapped out. Scientists now estimate there are only 19,000 different unique genes that make up our chromosomes. How to Sequence the Human Genome Video Most of your chromosomes are made up of what is commonly called “junk DNA.” This DNA doesn’t currently have a function and isn’t considered to be part of a gene because it doesn’t code for any building materials for the cell (aka proteins).

Interpreting the DNA Code Like Morse code, which has just two sounds, these bases can be put together in numerous ways to make the code of life. For example, Guanine-Cytosine Cytosine-Guanine Adenine-Thymine Guanine-Cytosine Thymine-Adenine For DNA that makes up our individual genes every 3 nitrogen base pairs code for a specific amino acid. Amino acids combine 3 at a time to form specific types of proteins. Cells are made up almost entirely of proteins so when you look in the mirror you are seeing the results of your cells reading your DNA and making specific proteins for your body.

Proteins and Amino Acids Proteins are large molecules that are make up of chains of amino acids. Proteins make up the cells that make up bodily tissues, such as muscle tissue and epithelial tissue. Many proteins have essential jobs that they perform inside of a cell. If a cell doesn’t have all the necessary proteins needed for life it won’t function properly. Amino acids are the building materials for proteins and come in twenty different types. For every 3 DNA base pairs a specific amino acid is created. These amino acids combine to form proteins. Your proteins combine to form cells……tissues…..organs……organ systems….and eventually an entire organism.

Genetic Mistakes=Genetic Mutations The first cells that combined to form you had DNA that was copied from your parent’s chromosomes. However every time our cells copy their DNA (chromosomes) they make mistakes. Let’s face it nobody is perfect and that applies to our cells as well. Your cells make mistakes but these mistakes aren’t very common. Human DNA has 3.2 billion base pairs that have to be copied when new daughter cells are being created. The proteins (DNA Polymerase) that copy your DNA make a mistake about once in every 100,000 base pairs. That means if copying your DNA was a test DNA Polymerase would get 99,999 out of 100,000. However that also means that when all of your DNA is copied 32,000 mistakes are being made. Most of these mistakes are made when copying “junk DNA” but sometimes mistakes can be made when copying essential DNA segments (genes). It’s also important to note that these mistakes are only important when reproductive cells are combining for the first time because those genetic mistakes will be part of the DNA for all of your cells. These genetic mistakes in humans create genetic mutations that all of us have. (We’re all MUTANTS!!!!!!!!) And we are all in some degree very slightly different from our parent’s genetically speaking.

Genetic Mutations Point Mutation is a change in a single base pair which changes one nitrogen base pair for another. Deletion Mutation occurs when genetic material is removed or deleted. A few bases can be deleted or it can be a complete or total loss of a chromosome. Insertion Mutation when genetic material is put into another region of DNA. This could be the insertion of 1 or more base pairs of DNA. Frame-shift Mutation is caused when insertion or deletion of genes is not in a multiple of 3. This then causes further problems with DNA sequencing down the line.

Gene Therapy Scientists have found where many genes are at on chromosomes. One way they do this is to fluorescently tag certain genes. Doing this then causes different genes to be fluorescent within organisms. Additionally individuals that suffer from certain diseases and disorders have a near identical code to one another within the genes that cause these genetic disorders. (Ex. Cancer, Sickle Cell Anemia, Cystic Fibrosis, etc.) Geneticists are now practicing a new type of medicine called gene therapy. They use viruses and bacteria to transfer healthy genes into cells that have unhealthy versions of those genes. Gene therapy can also be used to determine the gender of your child and certain attributes they will have. (hair color, eye color, etc.)