Download DNA - Doktorscience

DNA
• DNA stands for Deoxyribonucleic Acid and is found in
structures called chromosomes in the nucleus of cells.
• Chromosomes are made of both proteins and nucleic
acids, and when a cell is not dividing they are stored as a
spaghetti like tangle called chromatin.
• DNA directs everything a cell does and is the code that
dictates what proteins a cell makes
• DNA structure: a twisted ladder made of two
strands of nucleotides connected by hydrogen
bonds between the nitrogen bases of the opposite
nucleotides (these make the “rungs” of the ladder)
• The nitrogen base parings in DNA are always:
o Thymine + Adenine
o Guanine + Cytosine
Steps in DNA Replication
• For a cell to replicate the DNA must first double itself
by: unwinding, splitting in half, and then duplicating.
1. DNA unwinds
2. Hydrogen bonds between nitrogen bases break and
DNA “unzips”
3. New nucleotides (from the food we eat) are added
to each side of the now unzipped DNA by an enzyme
called DNA polymerase
4. Two complete DNA ladders now exist where only one
did before (each one is half the old strand, and half
new) This is called semi conservative replication