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Background: Nearly every cell in our body contains DNA, which is a very important molecule as it contains important genetic information that tells the cells in your body what to do.
The sequence of A, T, G, and C stores information on how to build and run your body.
The DNA structure is known as a "Double Helix."
DNA Double Helix
Deoxyribonucleic acid, known as DNA, is a self-replicating molecule that carries genetic information. All living creatures on the planet have DNA. It is found in the nucleus of nearly all cells in the body.
"Deoxy" means that it is lacking an oxygen atom on "ribose", a type of sugar.
"Nucleic" refers to the fact that this molecule can be found in the nucleus of each cell.
Lastly, the molecule is acidic.
Alleles, genes, and chromosomes are made out of DNA.
DNA Structure
DNA Structure
Francis H. Crick, James D. Watson, and Rosalind Franklin.
James D. Watson, an American biologist, and Francis H. Crick, a British biophysicist, originally postulated the double helix model in 1953.
Rosalind Franklin's X-ray diffraction images confirming the helical structure of DNA were shown to Watson without her approval or knowledge.
The men received the Nobel Prize. She did not. Big scandal!
Bases
Bases
Adenine
Adenine
Thymine
Thymine
Cytosine
Cytosine
Guanine
Guanine
A matches T and C matches G
A matches T and C matches G
3 hydrogen bonds connect G with C.
2 hydrogen bonds connect A with T.
Which pair of bases do you think has a stronger bond? G and C or A and T?
The answer is G and C. This is because there are 3 hydrogen bonds between the bases.
If 20% of a DNA sample was Adenine, how much of the sample would be Thymine?
The answer is 20% because A matches with T.
If 10% of a DNA sample was Adenine, how much of the sample would be Cytosine? The answer is 40% because A + T = 20%. That leaves 80% for C + G. Half of 80% is 40%
Erwin Chargaff - Discovered that the amount of A was the same amount of T. A = T and G = C!
Erwin Chargaff
Nucleotides
Nucleotides
Nucleotides are the smallest chunk or subunit of DNA. Each nucleotide is a monomer. Monomers link up to form a polymer.
Each nucleotide contains a sugar molecule (deoxyribose), a phosphate group, and a nitrogen base.
As you can see, the nitrogenous base rung of a DNA ladder connects directly with sugar. Sugar sticks to phosphates and bases.
DNA is made up of six parts: Sugar, Phosphate, A, T, G, and C.
A and T form a base pair. G and C form a base pair.
Nucleotides join together to make huge DNA molecules. DNA is a polymer.
The backbone or sides of DNA are made of alternating sugars and phosphate groups.
Deoxyribose sugar connects to phosphate as well as a nitrogenous base.
Information concerning how your body is built, as well as how it is supposed to function, is stored in the base sequence of DNA. In fact, the order of bases (A, T, G, and C) stores the information. The sequence of nucleotides stores the information.
A change in the sequence of DNA is called a mutation. Mutations can be neutral, beneficial, or harmful.
All lifeforms have the same DNA, but they develop differently because the number and arrangement of the bases are different in each lifeform.
DNA Polymer
DNA Polymer
DNA is a polymer – that means it is made from lots of small, almost identical, units called nucleotides.
During meiosis and mitosis, DNA becomes tightly coiled, and forms structures called chromosomes.
Humans have 46 chromosomes in their body cells, but 23 chromosomes in each gamete (sperm or egg cell).
DNA Replication
DNA Replication
When it is time for a cell to divide, DNA must be copied.
The molecule simply untwists and separates. As this happens, new nucleotides match up with each of the original strands.
The end result is 2 new DNA copies, each with a newer side as well as the older, original side.
Think of DNA as a reference book that cannot leave the library. The nucleus is like the library.
You can make a copy of the DNA, however. This copy is called messenger RNA, or mRNA. The copy goes to the ribosome which is like a 3-D printer, or factory.
Building supplies in the cells are amino acids. They are sort of like bricks, cement, wood and nails.
Amino acids are put in order on the ribosome to make protein, the finished product that used in the body. More information concerning protein synthesis can be found here.
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